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!

 

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

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

Plant of the Month: Gaillardia ‘Oranges and Lemons’

Gaillardia x grandiflora ‘Oranges and Lemons’

With low water use, an exceptionally long bloom season, and low maintenance requirements, Gaillardia x grandiflora ‘Oranges and Lemons’ is a great choice for your next landscape design project.

History

The plant was discovered in 2002 by Rosemary Hardy as a seed from Gaillardia ‘Dazzler’ and an unknown male parent. Patent number 17092 was awarded to the plant in 2004, and it has become a popular perennial choice since its commercial release. Unlike most blanket flowers, which sport dark orange or red ligules (a term for the “petals” of the composite inflorescences on Gaillardia), ‘Oranges and Lemons’ stands out with large, showy, light orange ligules fading to yellow at the tips.

Culture

This plant combines many of the ideals sought in planting design: low water use, low maintenance, abundant blooms, long bloom season, and sterility.

‘Oranges and Lemons’ prefers to be planted in full sun, with well drained soil in USDA zones 3-9. It has attractive grey-green foliage, but the abundant flowers are the main attraction. Even in the first year after transplant this cultivar puts on an impressive show that lasts and lasts. When grown in areas with frost, ‘Oranges and Lemons’ will bloom profusely and consistently from the time nights warm up in late spring to the first hard frost in fall. In areas with no frost, this Gaillardia can bloom virtually all year long! This is a sterile cultivar so, while some light deadheading could help make room for new flowers, removing spent blooms to prevent self-seeding is not a concern. The flowers and are highly attractive to bees, and the plant’s copious pollen and long bloom season means it is a great resource for pollen-seekers all growing season.

Once established, ‘Oranges and Lemons’ requires very little supplemental water, and can also withstand high heat. It has a compact habit, reaching 18” high x 24” wide (24” high with flowers). Unlike other Gaillardias which can flop open, ‘Oranges and Lemons’ will maintain its upright stems and mounding habit if planted in full sun. This cheery blanket flower can be virtually ignored in the landscape and still create a show-stopping display!

Design

‘Oranges and Lemons’ is ideal for containers, either by itself or in combination with trailing plants or dark-leaved grasses for contrast. It is also great for edging along pavement, although the significant number of bees it can attract may prevent planting along narrow sidewalks. The landscape pairing possibilities are endless, but it works particularly well with finely-textured purple-flowered plants such as the equally long blooming Nepeta x faassenii or Perovskia atriplicifolia ‘Little Spire’. The showy orange flowers are also a great counter-point to the foliage and texture of small, lower water use evergreens such as Abies concolor ‘Compacta’, or Juniperus squamata ‘Blue Star’.

Gaillardia companion plants

Gaillardia companion plants

Designing with Cactus

What is a Cactus?

Many people, even those who consider themselves familiar with arid plants, get confused when it comes to what really constitutes a cactus. Isn’t it basically anything spikey that grows in dry climates? No! A cactus is, in fact, a very specific thing.

Cacti are members of the family Cactaceae. There are approximately 1,800 species of cactus.

Two specific things set cacti apart from other plants:

  • Not all cacti have spines when they mature, but a great way of distinguishing a spiney cactus from other spikey plants in the field is the presence of “areoles,” little bumps on the plant from which clusters of spines grow. If the spines on the plant are not growing in clusters out of these bumps it’s not a cactus!

Cactus aerole

  • All cacti also have a specific flower structure. Though the flower of each cactus species may be very different, all cactus flowers have many tepals (a term used when the sepals of a flower are indistinguishable from the petals) that are somewhat fused; hundreds of stamens; and many-lobed stigmas.

Yellow prickly pear cactus flower

Designing with Cacti

As a group, cacti are drought tolerant and are a great option for any water-conscious landscape. But xeric gardens aren’t the only ones that can benefit from the use of cactus! Their frequently strong sculptural or geometric forms and punchy colors can add punctuation to any landscape design, as long as the growing conditions are right.

Cacti with upright or twisting forms are popular for use against a striking backdrop such as a richly-colored wall, or for their silhouette against a vista. They can also be grouped together for great large-scale textural effects, or consider pairing their chunky forms with something soft such as Mexican Feather Grass (Nassella tenuissima) for inviting contrast. Barrel cacti are perfect for creating rhythm and reinforcing patterns in design, and the bold textures and colors of pad cacti (Opuntia) provide great backdrops or focal points in the landscape.

Agaves, other succulents, and grasses are great design companions, but cacti can really be added to any composition with complimentary leaf colors, contrasting textures, and similar environmental requirements.

Most cacti are very sensitive to over-watering, so make sure the soil is very well drained, and the other plants in your design have compatible water use requirements. Use The Plantium to easily find great cacti and appropriate design companions for your next project!

Fun Facts about Cacti

  • All cacti are succulent, but not all succulents are cacti!
  • All cacti are native to the Americas, though they have spread around the world post-colonization.
  • Although they are typically slow growers, cacti are very successful in arid climates, so much so that in certain countries like Australia many cacti are considered noxious weeds.
  • Cacti grow in a wide variety of places, though mostly in habitats that experience some drought. People associate cacti with hot climates, but there are many species that are hardy to -30 deg. F and lower!
  • Cacti come in a wild variety of shapes, sizes, and forms, from the stereotypical Saguaro, barrel, and prickly pear, to the Rose Cactus (Pereskia grandifolia) which looks like a tree or shrub at first glance.
  • Most cacti don’t have true leaves, instead performing photosynthesis in their modified stems. However some cacti, like the rose cactus, can be very leafy!