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!

 

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

The Plantium: Changing the way the world sees plants.

Welcome to The Plantium! As landscape architects and designers we have always held a close relationship with plants. With the implications of a changing climate hitting close to home, this relationship with plants has never been more important. We are looked to by our clients and our peers to make appropriate plant decisions. While in years past these decisions may have been based heavily on aesthetics and survivability, we are now faced with making decisions that are better for the environment. This is a responsibility that we cannot take lightly. The links below are just the beginning of the resources available to help professionals recognize the impact of our design solutions. Resources like these are far and wide but we are still faced with the critical task of finding the right plants for the right situation and the right design solution.

At The Plantium we are committed to changing the way the world sees plants. Our tools help professionals make better choices in their plants and then easily communicate these decisions within their own company, to clients and other contractors. This tool will be a critical step in elevating the dialog around choosing, growing, planting and maintaining plants that now satisfy our aesthetic and environmental needs.

The Plantium. Find. Organize. Evaluate

Copyright 2014 Connect One Design

Related Resources:
Join us at #asla2015 booth- 1259
ASLA WEBSITE – GREEN INFRASTRUCTURE

ASLA WEBSITE – SUSTAINABLE RESIDENTIAL DESIGN: MAXIMIZING THE BENEFITS OF PLANTS