Soil Depth and Plant Selection

Minimum soil depth for plant growth is a frequent subject of discussion of late and while you cannot search The Plantium based upon soil depth, we thought we’d gather some information to assist in your criteria based plant designs!

Let’s first look at the question at hand. As designers and installers we are asked to create landscapes in all sorts of conditions. Often these conditions are challenging and not necessarily conditions that plants might face in their natural environments. That said, we have all seen these images at some point in our lives…. the beautiful and resilient plant that appears to be growing happily, in what appears to be NO soil depth AT ALL!

 

 

 

 

 

 

 

 

 

For those looking for answers regarding bed construction and just soil depth in general, let’s send you to one of our Plantium brands for some fantastic basic information regarding bed construction in the field.

https://www.provenwinners.com/learn/make-your-bed

Soil depth for OPTIMAL plant growth in more challenging situations such as green roof conditions, large planters, tree wells, etc. is dependent on four main factors. These factors are proper drainage, proper plant selection, plant longevity, and soil depth to plant height ratio. We’ll discuss these factors in this order because the very last issue you should be considering in your plant design is soil depth. If you have not addressed the first three issues in your bed design then regardless of soil depth, plants will not thrive.

Proper Drainage

Whether your planting bed is in the lawn, green roof or contained planters, proper drainage is crucial. While certain plants can survive inundation in a natural setting, standing water or improper drainage will QUICKLY de-oxygenate and compact the soil in contained situations and kill the plants. There are many ways to tackle drainage and all are dependent on the design situation. Working closely with the horticulture team is the best way to find an effective drainage solution.

Proper Plant Selection

Let’s look at those tough little plants growing in the cracks and crevasses! You need to keep in mind the type of plant you are specifying when dealing with challenging planting situations. Plants that grow in these conditions in the natural world tend to be tough, resilient, vigorous, and drought tolerant plants. If you have all the right soil and bed conditions but choose more sensitive plants, it is likely that those plants will struggle. Also, remember that as the soil profile for any plant is constrained so will the plant’s natural habit be constrained. Street trees planted in minimum soil volumes will never reach the full mature height or width that they would under optimal growing conditions.

 

 

Plant Longevity

Planting designs are being designed and installed with a maximum 20 year life span. A controversial statement, perhaps, so feel free to challenge it! It appears long gone are the days of an Olmsteadian landscape that appreciates with time and just barely reaches its full glory at 20 years. Here at The Plantium we vehemently disagree with this trend and firmly believe that criteria based plant selection can reverse this trend. Better plant choices! We’d love to hear your comments on this issue!

All that said, green roof and enclosed planter situations pose different challenges. Small planters and shallow green roof systems need very carefully management to maintain soil health and ultimately plant health. The shallower the soil profile the more quickly that soil will be depleted of nutrients and micro-organisms crucial to the plant’s health. If a refresh of the plant material (and soil) is planned over time, then shallower soil profiles can be a great fit. If the design contemplates trees and shrubs that are intended to grow to maturity over time, then a more significant soil depth should be considered.

Soil Depth

On to the question at hand. Let’s simplify the soil depth for optimal plant growth under container type situations into the following categories. Again, exact soil depth is probably debatable by many so we welcome other thoughts from our expert crowd!

Plant Type Plant Height Minimum Soil Depth
Annuals Any 3”
Turf Grass NA 4” (3” in warm climates)
Perennials <8” 4” (3” in warm climates)
Perennials 8”-16” 6”-8”
Perennials/ Ornamental Grasses/ Shrubs 16”-24” 12”-18”
Perennials/ Ornamental Grasses/ Shrubs 2’-6’ 24”
Shrubs/ Small Trees >6’ 3’ Minimum (should consider overall volume as well)
Trees All Should be calculated on overall volume for each tree and not just soil depth

 

Maintenance

Lastly, on-going maintenance is the greatest issue facing these planting designs. Over-watering is perhaps the most frequent maintenance faux pas committed against our container plants. Carefully working with the maintenance team is critical to head off this issue early on.

Happy Planting Y’all!

 

Connect One Design Shout Out

The Plantium is made for landscape professionals BY landscape professionals. To that end, it’s been an exciting summer in the Colorado mountains and the Connect One Design landscape architecture team has been hard at work. Check out Connect One Design in the media. We couldn’t do what we do without an amazing staff and The Plantium software!

Here’s just a few fun pics from the field. Enjoy!

 

Importance of the Allergy Friendly Landscape

Most of us think summer sneezing just ‘comes with the territory’ but did you know that you can alleviate some of it with an allergy friendly landscape!  As landscape professionals, the concept of an allergy friendly landscape is a crucial one. Regardless of the scale of a project our understanding of high pollen generating plants is critical to making some changes for the better in our cultivated landscapes.

Wind blown pollen

Wind blown pine tree pollen. Makes me sneeze just looking at it!

Background

Most of us suffer from just a little sneezing and sniffling from seasonal allergies but the implications of high pollen rates can be far more serious. “Deaths from asthma continue to climb each year at alarming epidemic rates”.1 While the causes of these increases can be debated it is clear that high pollen rates play a role in many health related issues, especially in the young, old and those with compromised respiratory and circulatory systems.

Studies have shown death rates among high-risk populations increase on days with high pollen and high pollution. Similar to the association of very hot or very cold weather to higher death rates, one cannot attribute it directly to the weather condition but rather see a correlation in high-risk populations.2 Impacts like thunder death outbreaks also bring home shocking impacts of high pollen in urban settings.3

So, how did we arrive at the increases in allergies and asthma? We all know the issue relates to high pollen counts, but what is pollen and has atmospheric pollen been on the rise in recent years? Pollen is the microscopic grain carrying the male gamete of a plant that will pollinate (via transport by insects, birds, wind, etc.) the female ovule of a plant. This microscopic grain is both an irritant and a nasal allergen in humans (and other animals; yup, dogs get allergies). Anemophilous plants generally cause the most allergies because they pollinate primarily by wind. The pollen grains of those plants are light and small, in order to be easily dispersed by the wind (and therefore tend to stay airborne and easily breathed in by humans). The role of female plants in an allergy friendly landscape is critical because they are attractive (for sure 🙂 )! The pistil of female plants is STICKY in order to capture the pollen grain. In an allergy friendly landscape female plants (and flowers) are important because they both do NOT produce pollen, AND they pull pollen out of the air with sticky attractiveness! Two other important aspects of pollen creation are important to understand as well – pollen production is increased dramatically with additional CO2 in the atmosphere (urban settings) and changes to the timing of pollen generation is being sparked by increased climatic temperatures.

Microscopic Helianthus Pollen

Microscopic Helianthus Pollen – it sure looks like it would irritate anybody’s nose!

So what does this have to do with the cultivated landscape and an allergy friendly landscape? This is where the concept of botanical sexism comes into our vocabulary. “Arborists often claim that all-male plants are ‘litter-free’ because they shed no messy seeds, fruits or pods. In the 1949 USDA Yearbook of Agriculture, which focused on trees and forests, this advice was given to readers: ‘When used for street plantings, only male trees should be selected, to avoid the nuisance from the seed.’ In the years following, the USDA produced and released into the market almost 100 new red maple and hybrid-maple-named clones (cultivars), and every single one of them was male.”4 At The Plantium, we believe male cultivars have an important place in the landscape, but it is important to understand that the use of male (and only male) cultivars and overall plant selection play the most important role in developing an allergy friendly landscape.

Scope and Scale

When and where it is important to think about an allergy friendly landscape? There are many projects where understanding the right plants for a low allergy and allergy friendly landscape are important. Being conscious of pollen generation on all your projects can help address the growing issue of high pollen in the cultivated landscape. Our responsibility as landscape professionals should be taken seriously! Consider your client when embarking on a residential design. Just asking the question about any allergy or asthma sufferers in the household (and then designing an allergy friendly landscape) can help make a successful landscape and a happy client. Allergy friendly landscape plant selection is most important around high risk populations, including playgrounds and senior living projects. Finally, projects in urban centers should be addressed carefully as the greatest population of allergy and asthma sufferers per capita reside in cities.

Amaryllis Stamen

Up close and personal on the Amaryllis stamen. The sticky pistil of an amaryllis flower gathers up all this pollen for fertilization!

Making Great Plant Choices

All of this background begs the question… what do we do now? Here are a few thoughts.

  1. Understand and educate yourself on the benefits of the allergy friendly landscape.
  2. Familiarize yourself with the OPALS rating system. Thomas Ogren created the first and only known rating system that ranks the allergy potential of plants.
  3. Discuss the need for an allergy friendly landscape with your client.
  4. Educate yourself on types of plants that might fit in an allergy friendly landscape and follow a few best practices such as:
  • Gender balance the landscape.
  • Use fewer wind pollinated species.
  • Encourage sterile cultivars and showy flowers (most plants with big colorful flowers are insect pollinated! Bees welcome?!).
  • Avoid high pollinators: male only willows, poplars, aspens, ash, (fruitless) mulberry, cypress, junipers, yews, myrtles, currants, etc., olive trees, Bermuda grass. Fruit trees are good but nut trees tend to be allergenic.
  • Develop maintenance manuals for your clients that encourages trimming of existing high pollinators and good maintenance of installed plants (e.g. trimming privet before it flowers). The Healthy Schoolyards Initiative5 has a great start at a list of maintenance measures that can be undertaken on existing landscapes.

The Politics of Allergy Friendly Landscapes

While it appears uncertain that low pollen ordinances are having an impact, landscape professionals should be aware that there are a growing number of urban centers enacting pollen control ordinances, including Pima County, AZ, Clark County, NV, Albuquerque, NM, Phoenix and Tucson, AZ, and El Paso, TX, among others. Other cities such as Louisville are embarking on some truly innovative approaches to understanding and addressing the epidemic.

Conclusion

While we can thank pollen for so many wonderful things like solving murders (it’s a plant’s fingerprint!), determining the age and quality of coal seams, and our delicious fruits and vegetables we now need to be stewards of our own air and address the issue of excessive pollen in our cultivated landscapes!

References:

  1. http://www.academia.edu/4110694/Politics_of_Pollen_Article Copyright 2001, Tom Ogren
  2. http://www.webmd.com/allergies/news/20000427/high-pollen-linked-death#1
  3. http://www.bbc.com/news/world-australia-38121579
  4. https://blogs.scientificamerican.com/guest-blog/botanical-sexism-cultivates-home-grown-allergies/
  5. http://www.healthyschoolyards.org/

Image References

https://commons.wikimedia.org

Xeriscape: A to X

Welcome, Soon-To-Be Xeriscape Experts

Even if you have never heard of xeriscape before now, this article will provide you with all the info necessary to confidently execute a xeriscape project, whether its for your client or in your own back yard.

For those of you already familiar with the concept of Xersicape, don’t worry! This post covers not just the basics, but also gives great details on elements of xeriscape with which you may not have been familiar.

 

What is Xeriscape?

zeroscape crop

Lets get this out of the way first. It is not ZEROscape! “Xeriscape” is a combination of the Greek word “xeros,” which means dry, and the word “landscape.” “Zeroscape” is a common mispronunciation and misconception that we will discuss more later in the article.

Xeriscape Definition:

Xeriscape is a system of principles to create gardens and landscapes that reduce, or even eliminate, the need for additional irrigation. Xeriscape is not a garden style, and it does not mean just rocks! Xeriscape principles can be applied in any region across the world.

Xeriscape History:

While Coloradans did not invent water-conscious landscaping, we did invent “xeriscape!” Denver Water, Colorado’s oldest and largest water utility, coined the term ‘Xeriscape’ in 1981 as part of an effort to make water-wise landscaping a recognizable concept. At the same time they assigned 7 simple, accessible principles to xeriscaping so that anyone creating or maintaining a landscape could incorporate water-conserving techniques.

Xeriscape Principles:

  1. Plan and design
  2. Plant zones
  3. Alternative turf grasses
  4. Soil amendment
  5. Mulch
  6. Efficient irrigation
  7. Maintenance

What is NOT Xeriscape?

Misconceptions

Xeriscaping has been growing in popularity across the country as a way to utilize water resources more sensibly, and create landscapes than can be beautiful and resilient in periods of drought. But misconceptions consistently stand in the way of many people’s acceptance of the concept.

 Misconception 1: Xeriscape is Just Rocks

Not ROcks

As we mentioned before, xeriscape is NOT “zeroscape”. Xeriscape does not mean replacing your lawn or traditional landscape with rocks or hardscape! A field of pavement or gravel does just about as much for your property value as dead grass, and provides even less environmental benefit.

Instead, xeriscape emphasizes:

  1. choosing plants adapted to the rainfall of your region
  2. grouping plants with like water needs
  3. reducing (not eliminating) turf area
  4. using efficient watering techniques to achieve beautiful landscapes

 Misconception 2: You Can’t Have Lawn

Xeriscape does not mean no lawn.

As the popular saying goes, xeriscape does not mean lawn-less, it just means less lawn.

We LOVE our lawn here in the US. While the total square footage of lawns is decreasing, a study done by a NASA scientist in 2005 suggests there are “three times more acres of lawns in the U.S. than irrigated corn” (approx. 49,000 square miles of lawn), which makes it the largest irrigated “crop” in the US by surface area. The lawn has been soliloquized as an aesthetic expression of Manifest Destiny. Whole collegiate majors are devoted to turf grass. This American love of lawn is one of the most prominent barriers to adopting xeriscape principles in residential landscapes.

But fear not! You can still have that patch of emerald green grass for your kids to play on, or even just for your dog to whizz in, by:

  1. carefully placing turf grass only where it will be used
  2. choosing grass species best suited to your climate
  3. watering efficiently

 Misconception 3: Xeriscape is all cactus and pokey things

Xeriscape is not just cacti

 

Just as xeriscape does not mean replacing your lawn with rocks, it does not mean only planting cacti. (Although check out this article to see how cacti can be beautiful in any landscape!)

Xeriscape entails selecting plants of all kinds that will thrive without requiring much additional irrigation. It is important to remember that this is based on the part of the country in which you are planting. Xeriscape plants for Colorado, which receives an average of 15 inches of precipitation per year, will be different than those for Arizona at 8 inches of precipitation, or Florida at 64 inches!

No matter what part of the country or state you live in, there is a large palette of plants, yes even non-pokey ones, which you can use to create a beautiful xeriscape in any style.

Misconception 4: Xeriscape Yards look Shaggy and Unmaintained

Xeriscape yards can be beautiful

The truth is that you can achieve almost any design aesthetic, from formal to cottage to meadow, using xeriscape principles and a combination of native and regionally adapted plants. There are myriad reasons to want a beautiful yard, from HOA requirements, to property values, to the all-important question “What will the neighbors think?!” When many people envision xeriscape, even if they aren’t thinking cactus and gravel, they think of a tangle of unkempt natives.  But in fact, a well-executed xeriscape project can be the envy of the neighborhood!

 

Why should I consider Xeriscape?

Beautiful Landscapes without the Extra Water

Yard Drought

The EPA estimates that outdoor water use (landscape irrigation, etc) accounts for 30% of our national water consumption. CSU estimates that in the arid west it can be as much as 55% to 60% of household water use, with most of that going on lawns.

Why is this important?

Whether or not you live in an arid region, droughts happen somewhere in the country every year. During droughts outdoor watering can be severely curtailed, and it can take a heavy toll on the beauty and diversity of home and public landscapes. By planting plants that are already adapted to the natural rainfall of your region, and that are also drought tolerant (can maintain their vigor during periods of less than normal rainfall), you can have a landscape that thrives even during water shortages.

A five-year study (YARDX) of 357 residential landscapes conducted by Metro Water Conservation, The Bureau of Reclamation, and 7 Colorado front range municipalities worked to quantify the water savings of xeriscape. It found that homes which utilize xeriscape principles, halve their current lawn, and plant ¼ low water use plants and ¼ medium water use plants reduced their outdoor water usage by an average of 30% and up to 50%.

Time and $$$$$$!

Water Value

Unless you are fortunate enough to be on a ditch or well, reduced water consumption directly results in money savings!

Another financial benefit of xeriscaping is increased home value. A study by the Virginia Cooperative Extension found that a beautiful landscape increased perceived home values among buyers by an average of 11%, and the numbers were highest for landscapes that were not exclusively lawn.

Finally, xeriscape requires less input of time and money (fertilizing, seeding, mowing, aerating, etc) than a lawn of comparable size. Why not free up those weekends for something other than lawn maintenance?

Let’s Get to Xeriscaping!

Now that you have a basic idea of what Xeriscape is and is not, and some idea of the benefit, lets dive deeper into the principles of xeriscape and how to take a xeriscape project from beginning to end!

Principle One: Plan and Design

Understand What You Want

As with any project, you’ll get a better product (and save a bit of money) if you take some time to flesh out the goals first. The initial design process for a xeriscape project is just like the process for any other landscape project:

  1. Create the program.
  2. Pick a style. As mentioned above, xeriscape is not a garden style. You can achieve any landscape style you like using xeriscape principles!
  3. Create a plan of hardscape and other improvements, and block out planting areas.

Principle Two: Plant Zones

Definitions:

Low water use plants – Plants that require no additional irrigation after establishment, based on the region’s rainfall.

Medium Water Use Plants – Plants that require a moderate amount of irrigation after establishment, based on the region’s rainfall. (One deep watering every 4 days in warm weather)

Step 1: Establish your Water Use Zones

Although xeriscape emphasizes plants whose water needs are in line with regional rainfall, this does not mean you can’t have higher water use plants and lawn in your landscape. Xeriscape groups medium- and low-water-use plants together maximize watering efficiency.

Spend your water where you spend your time

  • Focus higher-water-use plants in high-use areas such as decks, patios, paths, etc.
  • Also place higher water use plant in areas where water typically collects such as adjacent to downspouts, in low lying areas, or along ditches or ponds.
  • Concentrate lawn only where feet will be using it, and make it only as big as you need.

A good rule of thumb for many back yards is 1/3 low-water-use plants, 1/3 medium-water-use plants, 1/3 lawn. If feet aren’t using the front lawn then don’t include it! An appropriate front yard is more like 2/3 low-water-use plants, 1/3 medium water use plants. But the more you skew your ratios to low water use plants the more water you will save!

Based on your design, decide where to cluster water uses and where your lawn will be located. This will correlate directly with the irrigation system design, if one is being installed.

Xeriscape water use zones diagram.

Step 2: Pick Some Plants!

After you establish your water use zones, it is time to flesh out the planting design. Appropriate plant selections are not only key to saving water, but also to completing your design vision. This is where criteria-based plant design can really be an asset. Take some time to review this great article on how to make the best plant selections using criteria-based plant design, then use water use as one of your primary plant selection criteria.

Each state and region has resources available to help individuals and professionals choose plant material for xeriscape, many of which are easily searchable online. Several states have programs such as Plant Select, EarthKind, and Texas Superstar (part of EarthKind), and that help identify and introduce the best plants for specific regions. Or check out this list of resources from the EPA to get you started.

 

Principle Three: Alternative Turf Grasses

Alternative Turf Grasses vs. Turf Grass Alternatives

There are two distinct ways to treat lawn areas in xeriscape designs, based on your desires and the amount of foot traffic your lawn will receive.

If you want a true lawn for entertaining, playing, etc. explore your best regional alternatives to standard bluegrass. There are many varieties that will provide you a beautiful lawn with 30% to 75% less water.

If you like the idea of a space that you can occasionally walk across or just put a bench in you might consider turf grass alternatives. There are many that work well in each region and that require significantly less water and maintenance than traditional turf.

Xeriscape thyme lawn

Principle Four: Soil Amendment

We all know that the health of the plants in our landscapes largely depends on soil quality. So before you pop those new plants in the ground remember that almost all types of plants will benefit from the use of compost! Organic matter in compost helps sandy soils retain water better, and helps clay soils release water more effectively and drain more freely. In addition, compost will help replenish the nutrients in soil without the need for fertilizer.

The standard recommendation is 1 to 2 inches of compost over the area to be planted, tilled to a depth of 4 to 6 inches.

 

Principle Five: Mulch

Now the plants are in and looking beautiful, but don’t leave that ground between your new plants exposed! Mulch is a crucial part of any landscape or a variety of reasons. First, it looks much better than bare dirt.

Second, and more importantly, mulch:

  • keeps your soil in place
  • keeps your plant roots cool
  • prevents soil from crusting
  • minimizes evaporation
  • reduces weed growth

Organic and inorganic mulch.

Mulches come in two types: organic, such as fiber, bark, pine needles, etc; and inorganic, such as rocks and gravel. Both types serve the same ultimate purpose and have their own advantages, so your ultimate choice should depend on the desired landscape style.

Organic mulch should be applied 4 inches deep, and inorganic mulch should be applied 2 inches deep.

Principle Six: Efficient Irrigation

The purpose of xeriscape is to reduce the amount of water you need to apply to your landscape. In some cases, you can even eliminate watering altogether! But almost no freshly-planted landscape can thrive in its first two years without additional water.

Establishment Irrigation

Because they have not established a mature root system, transplanted plants almost always require supplemental irrigation during for the first two years after planting. This is true for all transplanted plants from trees to groundcovers. If done correctly, providing your landscape with some additional water during these first two years ensures long-term vigor and the growth of a healthy root system.

While your plants will need slightly more water in these first two years, remember not to kill them with kindness! Keep in mind the overall water use requirements of your planting areas (your plant zones) Low water use plants need only small amounts of supplemental water in their establishment phase, whereas your medium-water-use plant areas will need more.

There is a Wrong Way to Water

Whether manual or automatic, the most important things to remember about irrigating any landscape, but especially xeriscape are:

  • Respect your zones
  • Choose the right delivery method
  • Water at the right time

Zones

Your xeriscape will only use less water if you give it less water! Don’t throw your work creating plant zones out the window by watering everything equally. If a new irrigation system is being included in your project make sure it is zoned according to your water use plan.

Water Delivery Method

Xeriscape can be irrigated efficiently by hand or with an automatic sprinkler system. Regardless of how you water, it is important to choose the most efficient water delivery method.

Fundamentally, the best irrigation:

  • Waters deeply and slowly, allowing water to soak in rather than run off.
  • Delivers large drops of water close to the ground, thus reducing water loss due to evaporation.

Avoid watering systems that throw water high in the air or release a fine mist.

Below are common recommendations for each planting area type:

  • Grass: Use gear-driven rotors or rotary/high-efficiency spray nozzles that have larger droplets and low angles to avoid wind drift.
  • Trees, Shrubs and Perennial Beds: Use low sprays, drip lines or bubbler emitters

For much more in-depth information about watering systems and calculations check out this article from the “Water – Use It Wisely” conservation campaign.

Examples of efficient irrigation methods for xeriscape.

Timing

The following principles apply to frequency and duration of watering your xeriscape to maximize efficiency and create the most robust root systems:

  1. Never water between 10 am and 6 pm, when water loss due to evaporation will be the highest. Watering late at night or early in the morning reduces this loss, and gets the plants ready for the day.
  2. Water more deeply but less often. Frequent shallow irrigation encourages shallow, less vigorous root systems, and leaves the plant more susceptible to drought stress. Conversely, reducing watering frequency and making sure that the water penetrates deep into the soil encourages more vigorous and robust root systems in all your plants, but especially trees and shrubs.
  3. Water-rest-water. As part of allowing water to penetrate more deeply, water each area in intervals. By taking a “water-rest-water” approach, you allow more water to soak into the root zone, and loose less to runoff.

Weather

Don’t forget that you are not the only source of water for your plants! If it has been rainy, cool, or cloudy, your plants will have taken up and lost less moisture, and will therefore need less irrigation. If you have an automated irrigation system, install rain and soil moisture sensors to prevent excess irrigation. If you are watering by hand, you can get tensiometers or use the time-honored “poke a finger in the soil” trick.

Don't be this guy.

Principle Seven: Maintenance

Depending on the design style, xeriscape can be very low maintenance. But we all know there is no such thing as a no-maintenance landscape!

If you have chosen to include it, the lawn will likely still require the most input of time and materials in your xeriscape. Turf requires spring and fall aeration along with regular fertilization every 6 to 8 weeks. To reduce the amount of weeds in your lawn, and reduce its water needs:

  • keep the grass height at 3 inches
  • allow the clippings to fall.

Incidentally, according the NASA study, this also dramatically increases the carbon storage capacity of your lawn!

Aside from the lawn, there are the normal chores of weeding, pruning, trimming, etc that are inherent in any landscape. The intensity of these tasks depends most on your landscape style, but don’t forget to compost the yard waste for reincorporation into your landscapes each fall!

 

Ta Da! You’re an Expert

Now you know: xeriscaping is not mysterious or difficult. With a little bit of forethought, you can have a beautiful landscape and use less water while you’re at it! Go forth and xeriscape.

 

Other Resources

Designing with Dog Friendly Plants

Ever wonder how we get our yards, parks, and streetscapes to be ‘dog friendly’? As in, how do we design a urine and trample resistance landscape filled with dog friendly plants? Well, let’s start with thinking about some alternative groundcovers that can take a little beating. These are plants that can be used as an alternative to turf. Turf alternatives can save water AND help fight off the brown patches that come with a ‘dog heavy’ landscape. A couple good examples in the attached pdf include Elfin Thyme and Ajuga. These are just two great choices, but you can always use your filter criteria and select low growing plants that can withstand foot traffic. In The Plantium’s filter criteria you’ll find the foot traffic filter under ENVIRONMENT.

The second issue is urine resistance. While this is NOT a filter in The Plantium, the attached pdf has some tried and true choices that can withstand the excessive nitrogen content in dog urine. Again, not an exhaustive list but a good start. Remember to also consider any plants that are TOXIC to pets and avoid those. Sending your little furry friend to the vet would definitely NOT be considered dog friendly plants! For those Plantium users, this is a filter criteria under WILDLIFE. For those of you not yet in The Plantium you can visit the ASPCA site (Plantium’s filter criteria is WAY easier, though!) 🙂

Lastly, and perhaps most obvious would be water. The faster you can wash away any leave behinds from the doggie visitors, the better chance of avoiding the burn spots, so let’s take back those brown patches and get into our dog friendly plants!

Dog Friendly List

https://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants

 

Designing with Bulbs

We’ve all read some great articles about designing with bulbs (and corms) so why not keep the discussion going? Designing with bulbs can be daunting. Visiting the botanic gardens in spring nearly blinds us with the glory of huge swaths of spring bulbs. Vast beds of daffodils, crocus and tulips are the sure sign that spring has sprung. A bed of crocus dusted with snow is an iconic image of early spring. Now let’s focus our attention on some other aspects of designing with bulbs, year-round interest and designing to specific bloom heights.

5177_WPFL_Eremurus-himalaicus-WMC_001Dahlia 'XXL Veracruz' AZTEC

The opportunities presented by designing with bulbs can be taken advantage of year-round with a little planning and great execution. Gladiolus and Dahlias can bring in a huge color punch during the mid-summer to late summer in warmer climates and similarly Allium and Autumn Crocus in colder climates. Similarly, lilies can provide a tremendous amount of foliar interest in the early summer months and then finish the season off with splendid color in late summer and even through the fall. The first step is to sort through the vast array of choices in bulbs and corms and remember what you are trying to achieve. Here a sampling of a season-long list for a garden in zone 6a, that’s scented, and attracts bees, hummingbirds, and butterflies. This short list from The Plantium yields plenty of choices to keep you thinking about designing with bulbs all season long! There are so many more to choose from!

Bulb Flowering Season

The next consideration is careful planning around bloom height. This same list now includes plant (foliar) height vs. actual bloom height. Not planning for the bloom height of late blooming bulbs is a common mistake. Some height variations will be minimal but some can be more than a foot or even up to 4’! Check out the Foxtail Lily. Many of these bulbs are not known for lush foliage so you can place them further back in the garden (than you might normally based solely on foliar height) with other perennials or shrubs around them. This leaves their bloom to surprise us when the time is right!

Bulb Flower Heights

Using Denitrifying Plants in the Landscape

Turns out we have an addiction in this country. “Call it the nitrogen fix. It is like a drug mainlined into the planet’s ecosystems, suffusing every cell, every pore — including our own bodies.”1 In response, some jurisdictions (apparently finding dealing with addiction at the source – i.e. agriculture, wastewater, feed lots, poor landscape practices, etc. too difficult) are requiring the end user of non-potable reclaimed effluent to utilize only denitrifying plants in the landscape. Their theory being that if the ornamental plants can take up the nitrogen, then problem solved.

This discussion of overabundance of nitrogen in our water and soil could get really scientific, really fast (and unfortunately make for very dry reading) so instead I’m going to keep things pretty simple and straightforward and provide some great resources for seeking additional information.

The nitrogen problem. “Over the last century, the intensive use of chemical fertilizers has saturated the Earth’s soils and waters with nitrogen. Now scientists are warning that we must move quickly to revolutionize agricultural systems and greatly reduce the amount of nitrogen we put into the planet’s ecosystems.”1 Excessive nitrogen leaches into waterways, feeds algal blooms and contributes to eutrophication of water systems….. effectively starving plant and aquatic life of oxygen. It can even starve our children of oxygen, known as Blue Baby Syndrome, as a result of nitrogen contaminated drinking water.

The good news. Nitrogen is an inorganic compound which, unlike other macronutrients, can be turned to gas and released into the atmosphere. More good news. This means that the use of denitrifying plants can be addressed via phytometabolism in a relatively short period of time and presents good opportunities for field application.2 “Since all plants use nitrogen and support denitrifying bacteria, any kind of plant can provide some form of nitrogen remediation from soils and water. However, the method that provides the quickest remediation tends to be a system that includes plants with very high growth rates and evapotranspiration rates. Nitrogen is used up quickly, or the plant acts like a large reactor, priming the soil bacteria for speedy conversion of the nitrogen into a gas. Plants species that produce a lot of biomass have been those most successfully used in studies to remove high levels of nitrogen in soils and groundwater.”3 Some would then argue for the use of bluegrass and other fast growing turf, but studies have shown that a mixed species landscape will produce a more diverse microbial soil, and therefore denitrify faster via plants AND bacteria.

Finding the right plants. While in no way an exhaustive list, the book Phyto: Principles and resources for site remediation and landscape design, suggests a brief list of high biomass plants such as Bambuseae, Brassica juncea, Brassica napas, Cannabis sativa, Linum usitatissimum, Panicum virgatum, Populus, Salix and Sorghum. Additionally, some high evapotranspiration-rate plants include Alnus, Betula, Eucalyptus, Fraxinus, Populus, Salix, Sarcobatus vermiculatus and Taxodium distichum. Again, while not an exhaustive list one thing to note is that these tend to be high water use species. In a large scale remediation setting this is desirable (because you are purposefully applying large amounts of contaminated water), however, it tends to fly in the face of end user goals in the ornamental landscape that are working hard to reduce overall water consumption.

Unfortunately, it would seem that municipalities, especially in drought plagued areas trying to encourage water reuse, may end up further discouraging effluent reuse with these unnecessary regulations and may find themselves dealing with unintended consequences, such as forcing the use of plants that require even more water to both thrive and denitrify the soil. It is clearly a discussion worth continuing.

 

I’d like to thank Kate Kennen for the amazing information gathered from her book for this article. Kate is always an inspiration and this book is an INCREDIBLE resource for all practical applications, large or small, for phytoremediation and productive landscapes. It is a must read!

Find Kate here….  http://offshootsinc.com/

Find her book here…. https://www.amazon.com/Phyto-Principles-Resources-Remediation-Landscape/dp/0415814154

  1. Fred Pearce. Copyright 2009. http://e360.yale.edu/mobile/feature.msp?id=2207
  2. Kate Kennen and Niall Kirkwood, Phyto: Principles and resources for site remediation and landscape design. Routledge, 2015. Figure 3.1, Page 63
  3. Page 128

Sourcing Plants – New Plant Availability Feature (beta)

Sourcing plants is about to be easier than ever!

UPDATED 5/1/17

Just choose your state and see all of The Plantium’s participating nurseries. Don’t see your favorite nursery? Just complete the form and get their information on our site as soon as possible! You can now also export existing plant lists as a spreadsheet, including availability.

Colorado Nurseries

Plant availability is live on The Plantium. Do you want to sign up a nursery that you frequently go to for plant material? Send them this link. Fill out the quick easy form and we can list that nursery’s stock for FREE! ENJOY!

For Nurseries

Plant Availability (beta) is LIVE! Sourcing plants can be the most disheartening part of planting design.  As a landscape architect I cannot think of anything more frustrating than spending hours choosing just the right plants for a project only to have my contractor or nursery supplier come back and tell me they cannot find half of what I specified. It drives me crazy!

That is why we are so excited to launch the new Plantium availability feature (beta) in Colorado, Utah and beyond. Landscape professionals in these states will soon be able to search for great plants, make lists, evaluate their designs AND locate those plants at nearby nurseries. While only in beta version right now, we are thrilled to make finding plants just a little bit easier. This plant availability feature will be live in the coming weeks. Start your free one month trial now, and take advantage of your free web training session so you can be ready to take full advantage of this new time saver as soon as it hits the primetime!

Thanks and Happy Plant Hunting!

By Heather Henry, President and CEO of The Plantium

Understanding Nursery Stock Sizes

It’s time to build your plant lists…. And there’s one thing to remember. Size matters! But understanding and deciphering standard nursery stock sizes can be like trying to find your way out of an Iowa cornfield. You’re bound to get lost a few times. Everyone calls out nursery stock sizes differently. Gallons, flat size, tree height, or caliper have all appeared in our plant lists. But depending on your familiarity with the nursery industry, you may not know that there is a continuously updated national standard on how to spec nursery stock sizes!

When writing this blog, I set out to include a nice handy, dandy all-purpose cheat sheet for our landscape professionals but it turns out that is easier said than done! Instead, this article provides a brief overview of the standard and can get you started on the right path to learning more for the next time you specify plants. We cannot promise that your suppliers will be following this standard to the number and letter, but if you stay familiar with the standards you will be much more likely to specify the nursery stock sizes that are available.

Specifying the Right Sizes Takes Knowledge

Specifying the Right Sizes Takes Knowledge

Called the American Standard for Nursery Stock, this national standard is published and maintained by AmericanHort, which is a somewhat recently formed consolidation of the American Nursery & Landscape Association and OFA—The Association of Horticultural Professionals.

According to AmericanHort, “The purpose of the American Standard for Nursery Stock … is to provide buyers and sellers of nursery stock with a common terminology, a ‘single language,’ in order to facilitate commercial transactions involving nursery stock. For instance, the Standard establishes common techniques for (a) measuring plants, (b) specifying and stating the size of plants, (c) determining the proper relationship between height and caliper, or height and width, and (d) determining whether a root ball or container is large enough for a particular size plant.”

The organization has been publishing this nursery standard since 1923, and it was adopted as a national standard in 1949 (ANSI Z60.1-2014). The most recent revision to the standard was published in 2014, and is available free from AmericanHort HERE. Use of this standard when growing and specifying plants is voluntary, but it is widely accepted and often referenced in standard specification sections. Using the standard has many benefits for designers and contractors, not the least of which is simplifying the procurement and acceptance processes by relying on clear pre-defined standards for quality and size of nursery stock.

The complete standard may be a daunting 109 pages but it is a surprisingly easy read, and provides in-depth, but digestible information. Below are a few key points from the American Standard for Nursery Stock you may find helpful (along with a cheat sheet to get you to the appropriate tables in the larger document). However, we would HIGHLY recommend reading through the whole standard and having a copy handy. It truly provides an amazing wealth of info (there’s a great section on identifying unacceptable co-dominant leaders – a problem I’ve had first hand issues with!). This resource also provides all the information necessary when accepting or rejecting plant material that shows up at your site!

 General Standards for Nursery Stock Sizes:

  • Specifications must include plant size by caliper, height or width appropriate to the plant type.
  • Certain plants may be specified by container size (see below). ALL others should be specified with caliper, height or width.
  • Typically, plant size specifications should include only the minimum allowable plant size in that interval. In other words, if you specify a 2.5 in. caliper Type 1 shade tree you may get a tree anywhere up to a 3 in caliper because it references the 2.5 to 3 inch range for that type of tree. As long as you specify the minimum, you know you will not get a SMALLER tree.
  • Caliper is always measured six inches above ground or soil level for trees less than 4.5” caliper, and 12 inches above the ground for 4.5” or larger.

General Standards for Containers:

  • These are generally the only plants to specify by container size
    • Herbaceous perennials
    • Non-winter-hardy shrubs
    • Ornamental grasses
    • Groundcovers
    • Vines
  • Containers marketed and sold with a # designation must have volumes within the ranges shown in the ANSI standard in order to comply
  • Container classes #1 through #100 include the volume of a container that, if such a container were manufactured, would hold the equivalent number of gallons as the container class number. #1 = one gallon; #5 = five gallon and so on.
  • Nursery stock specifications that reference only an imperial volume measurement, such as “quarts” or “gallons,” are not in accordance with the Standard. I can tell you that our plant lists have gotten that WRONG for years!!
  • The SP designation refers to ‘small plant’ containers. #SP4, for example, is a 4 inch container, or “quart” container. This designation goes from #SP1 – #SP5 and should reference square or round.
  • Container grown nursery stock shall have a well-established root system reaching the sides of the container to maintain a firm ball, but shall not have excessive root growth encircling the inside of the container (the same holds true for roots in ball and burlap!).

 

Root Bound

Container Growth Gone Wrong – Root Bound Tree

Tree B&B

When Done Right – A Thing of Beauty

 

Shade and Flowering Trees:

  • There are FOUR types of shade and flowering trees identified in the standard with the following associated specifications tables
    • Type 1 – Page 15-16
    • Type 2 – Page 17
    • Type 3 – Page 19
    • Type 4 – Page 21
    • Multi-stem and Shrub Form Trees – Page 24
  • Multi-stem tree specifications should include a minimum number of stems. If none is specified, 3 will be assumed.

Deciduous Shrubs:

  • There are THREE types of deciduous shrubs identified in the standard with associated specifications
    • Type 0 – Page 28
    • Type 1 – Page 28
    • Type 2 – Page 29
    • Type 3 – Page 30
  • Plants may not meet plant size specification or minimum number of canes at time of shipment at certain times of the year, but would be expected to reach the plant size specification and minimum number of canes during the first growing season after shipment.

Coniferous Evergreens:

  • There are SIX types of Coniferous Evergreens identified in the standard with associated specifications
    • Type 1 – Page 32
    • Type 2 – Page 33
    • Type 3 – Page 34
    • Type 4 – Page 36
    • Type 5 – Page 38
    • Type 6 – Page 40
  • Coniferous evergreens will also be described by their shearing:
    • Natural: (showing the form natural for the species)
    • Semi Sheared (sheared when plant is young to maintain symmetrical shape)
    • Sheared (pruned regularly to retain a symmetrical shape)
    • Altered Form (Can you say POODLED!!)

Broadleaf Evergreens:

  • There are SIX types of Coniferous Evergreens identified in the standard with associated specifications
    • Type 1 – Page 42
    • Type 2 – Page 44
    • Type 3 – Page 46
    • Type 4 – Page 48
    • Type 5 – Page 50
    • Type 6 – Page 52

Additional information in the standard provides specs for young plants, roses, palms (and other bare root stock), fruit trees, bulbs, corms/ tubers, and understock/seedling trees and shrubs.

Now, armed with this great information, you can confidently go forth and specify!

Also, check out these other great articles regarding considerations on transplant size:

https://www.michigan.gov/documents/dnr/Influence_of_Tree_Size_on_Transplant_Establishment_277656_7.pdf

http://www.ncufc.org/uploads/Tree_Establishment_A_Review_of_Some_of_the_Factors_(Struve_2009).pdf

Urban Horticulture in a Capital Place: The National Botanic Garden

By, Arabella Beavers, Busy Beavers Gardening. Why would urban horticulture be important to The Plantium roving gardener? As our climate changes, as gardeners our ability to respond to these changes in a sustainable manner has to stay current and relevant. Urban horticulture is the study of the relationship between plants and the urban environment. It focuses on the functional use of horticulture so as to maintain and improve the surrounding urban area.[1] Staying current with the sustainability aspects of horticulture and gardening means being inspired by its new trends.

My inspiration this spring came from our nation’s capital and the gardens of Washington, DC. An amazing tribute to the history of gardens and an inspiration to the future of sustainability in urban horticulture the National Botanic Garden can’t help but stir the gardener’s imagination.

I was fortunate enough to visit Washington, DC and although the weather was a little inclement for spring, I was so delighted to find such spectacular gardens in our nation’s capital. From urban gardens along the city streets to sculpture gardens and the glory that is housed in the National Botanic Gardens – this city definitely is in touch with its green side. The United States Botanic Garden (USBG) is a botanic garden on the grounds of the United States Capitol in Washington, D.C., near Garfield Circle. The Botanic Garden is supervised by the Congress through the Architect of the Capitol, who is responsible for maintaining the grounds of the United States Capitol. The USBG is open every day of the year, including federal holidays. It is the oldest continually operating botanic garden in the United States.

USBG Entrance

The Courtyard Entrance, National Botanic Garden

 

Here’s a little history on this historic garden. The garden began as the Botanical Garden of the Columbian Institute but became the United States Botanic Garden in 1850, thirteen years after the demise of the institute. In 1867, Congress provided money for the construction of the first greenhouses. Constructed by the Architect of the Capitol in 1933, this historic Lord & Burnham greenhouse contains two courtyard gardens and 10 garden rooms under glass, totaling 28,944 square feet of growing space. Several historic trees stood on the site including the Crittenden Oak which marks the spot where John J. Crittenden made an address in an effort to avert the Civil War. Others included the Beck-Washington Elm which was a scion of an elm earlier planted by Washington himself. There was also a plane tree which Thaddeus Stevens brought from the Vale of Cashmere, a sycamore planted by Senator Daniel Voorhees, a Chinese oak from the grave of Confucius, two cedars of Lebanon, and several others that have historic associations.

The Bartholdi Fountain, the work of Frédéric Auguste Bartholdi, the same sculptor who designed the Statue of Liberty in New York Harbor stood in a central site in the gardens, however, it was placed in storage for several years to make way for the memorial to General Meade, the hero of Gettysburg.

The garden “was formally placed under the jurisdiction of the Joint Committee on the Library of Congress in 1856 and has been administered through the Office of the Architect of the Capitol since 1934. The Architect of the Capitol has served as Acting Director of the United States Botanic Garden and is responsible for the maintenance and operation of the Garden and for any construction, changes, or improvements made.” [2]

Today, the United States Botanic Garden is home to almost 10,000 living specimens, some of them over 165 years old.

USBG and Capital Dome

The National Botanic Gardens with Capital Dome Behind

Enough with the history…. Here’s my camera eye view of the experience that I had at the USBG on that wonderful ‘April Showers’ day…..
Nestled Within the shadows of The Capitol – currently under a state of repair, this lush garden was displaying its last flush of spring bulbs and beginning to prepare for a perennial push. With some exceptional displays of roses, iris and flowering bushes such as fragrant aballia. I was so excited to see this wonderful array – especially since it was still snowing back in Colorado!

Rose in USBG

Rose Specimen in the Rose Garden

The irises were particularly beautiful at this time of year, with the Iris tectorum ‘Alba’ being stunning in white and another favorite, the traditional bearded iris, in an array of colors that reminded me of a Monet masterpiece I had just seen in the National Gallery. There was even an iris called the red velvet Elvis iris, sadly not yet in bloom!! While plants such as the Iris tectorum can be hard to find, think about more common ones such as the Iris ‘Immortality’ to achieve the pure beauty of the white iris. https://shar.es/1l6uCg

Iris Specimen in NBG

Blooming Iris at USBG

Iris in Bloom

One of the things I loved so much was that they had many specimen plants – one of my particular favorites was this daisy – the Erigeron pulchellus var. pulchellus ‘Lynnhaven Carpet’, a wondrous woodland plant.

Erigeron pulchellus var. pulchellus 'Lynnhaven Carpet'

Erigeron Specimen

Continuing my walk through, I was particularly impressed by their water gardens with a contemporary gazebo and lovely plantings. It was alive with birds and a pair of mallards taking a bath in the shallow ponds. Examples of water grasses, lilies and water iris were just stunning.

Water garden 2 NBG

The Water Gardens, USBG

The Water Gardens, National Botanic Garden

Moving on through this delightful place, I was getting a soaking of my own as it was turning out to be a wet English type day – so I headed toward the greenhouse conservatory to see what I could find in there. Boy was I in for a colorful treat! It was like entering Aladdin’s cave, magical hothouse full of blooms and delights for the garden enthusiast.
The formal ponds within the main entrance are bedazzling – azure pools surrounded by bright pink azalea’s, orange orchids and surrounded by citrus trees – it was like a mirage. But this is a real garden and its microclimate creates the perfect temperature and humidity for the array or orchids and bromeliads clinging to the exotic trees they call home. At the end of each pool was an extraordinary living wall that contained more orchids –  a tropical display that was stunning to me.

Water Garden_USBG

Indoor Formal Water Gardens

Orchids 2 NBG Orchids_Closeup 2 NBG

Orchids in the Tropical Garden

Orchids in the Tropical Garden

 

As you can see from these close up images, these are not the orchids you buy at the supermarket!!

The national botanic garden houses many specialized gardens with displays including a Mediterranean garden, tropical gardens, desert gardens, tundra and a children’s play garden – something for everyone.  What I liked about it the most was that it had such a diversity of plantings.  Plants that we all know and love and use regularly in our gardens, such as lavender, to really unusual varieties that have been nurtured from far off lands form these magnificent displays.

 

 

Med Garden at USBG

Mediterranean Garden in the Conservatory

This really is a spectacular place and somewhere that I would love to return.  Seeing these magnificent displays not only left me wondering about the hundreds of hours of maintenance these gardens would take – but also how inspired I now am to travel and explore gardens all over the world. The challenge of seeing these plants in their natural environment, just as nature intended, then translating them to the urban horticultural environment is a challenge I am ready to take.

I leave you with some interesting facts and more information – next time you are in DC make sure not to miss these glorious gardens.

https://www.usbg.gov/

Happy Planting!

Arabella Beavers, Busy Beavers Gardening

https://www.facebook.com/Busy-Beavers-Gardening-LLC-201131763257382/?fref=ts

Aspen, Colorado

©ARABELLA BEAVERS, 2016

  1. Tukey, HB Jr. (1983). “Urban horticulture: horticulture for populated areas”.HortScience: 11–13.
  2. https://www.usbg.gov/brief-history-us-botanic-garden
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