Tall Pots

8/17/2019 Tall Pots

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I’m drawn to the call of frogs congregating on a

lone desert tree - the only dry anchor they can

find. The tree stands isolated, on an island cut

from recent eroding floodwaters. A muddy river

now separates me from this last tree standing in a

landscape scoured by downed limbs, tumbling

rocks, and long discarded man-made debris.

Yesterday, this expanse of desert in Maricopa

County was silent, dry, and sparsely vegetated.

The natural desert plants must have been cleared

years ago for a farm or perhaps a housing devel-

opment on the edge of Scottsdale. Now it’s barren

land. Had the native mesquite, creosote, palo

verde, rabbit brush, and various cacti been left

undisturbed, the established network of deep na-

tive plant roots may have weakened the recent

torrent’s damage. Unfortunately, damaged land-

scapes like this are common in disturbed desert

environments. But the Flood Control District of Mari-

copa County hopes to combat the destruction. One

tree at a time.

Tall ots in a Shallow World

Scientists have figured out how to restore damaged urban desert landscapes with na-

tive plants that use less surface water and prevent erosion. Problem is, the scraggly lit-

tle saplings with long roots just aren’t as pretty as their conventionally grown counter-

parts.

Wayne Warrington

8/17/2019 Tall Pots


An obscure and time-tested solution

The salvation of flood-ravaged desert landscapes lies

in an obscure but time-tested planting method for

native plants. A decade ago, the county embarked on

an experiment to plant native trees and shrubs in tall

pots, hoping to create plants with more robust root

systems better adapted for our arid climate. Since

native plants have a natural propensity to create root

structures that seek ground water dozens of feet be-

low the surface, it made sense to pot new desert

plants in a way that encouraged long root structures.

Conventional growing methods, conversely, create

unnaturally dense balls of matted roots. While they

may be hearty to start with, they struggle with a

shallow root structure in the harsh environment of

the Sonoran desert. But the rub is that native plants

transplanted from tall pots are not immediately

pretty. During the early growing phase, plants trans-

planted from tall pots have reduced foliage, thanks

to their long roots.

The longer root structure allows vegetation to anchor

itself in the desert soil, while reaching for the water

table that may lay dozens of feet below the surface.

Such an anchor provides additional support for fledg-

ling or established trees in fierce winds that can occur

during the height of monsoon storms. Anchored plants

also hold soil in place and retain healthy populations of

vegetation, allowing wildlife, like chorusing frogs, to

remain dispersed, instead of clinging to islands.

The tall pot nursery

Harry Cooper, the Flood Control District’s landscape

architect, inherited the tall pot experiment in 2014. His

inheritance included a tall pot tree nursery, an office

stocked with bookshelves and file drawers containing

related materials, and a collection of digital data.

I met with Cooper early on a windy morning in mid-

October, in the Flood Control District building in the

county complex in south Phoenix. Smells from the

landfill directly to the south become noticeable each

time the wind picks up.

Cooper’s voice is deep and gravely, and his profession-

ally proper greeting reinforces his serious demeanor.

I’m interested in looking at his data, but he’s eager to

showcase the tall pot nursery. We cross the agency

parking lot to a fenced off plot of land marked

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“Maricopa County Flood Control District Tall Pot

Nursery”. He unlocks the gate and leads me to rows

of vegetation growing in 30-inch sections of PVC

pipe. Standing amongst the scraggly sapling and

yearling trees, I wonder where the notion of incubat-

ing native plants in tall pots began.

The modern development of growing methods em-

phasizing elongated roots had originated in southern

California during the 1980s in experiments in arid

lands restoration. The tall pot tubes surrounding

Cooper and me were developed from planting prac-

tices started in Joshua Tree National Park, were im-

proved by research conducted by David Bainbridge

in San Diego, were transported to Arizona by way of

revegetation specialists at Arizona Game and Fish

Department, and were shared with the Center for

Native and Urban Wildlife at Scottsdale Community

College before ultimately being embraced by Mari-

copa County’s Flood Control District. And, while

it’s still relatively unheard of today, it boasts an en-

viously high survival rate.

Once considered impractical and improbable, arid

lands restoration projects have become examples of

ingenuity and successful persistence.

If climate changes, tall pot plants will fill valuable role

If monsoon storms continue to intensify and prolonged

high temperature periods increase, plants grown with

minimal water and robust roots will fill a valuable role

in and around Phoenix.

Richard Adkins, forestry supervisor for the city, is

charged with managing its urban forest. In an interview

with azcentral.com, Adkins admits that the largest chal-

lenge he faces is lack of citizen awareness of the exis-

tence and benefit of Phoenix’s urban forest. Surprising

and frustrating, since a 2013 inventory documented

over 92,000 trees, palms, and tall cacti within the city.

The U.S. Department of Agriculture says urban forests

cool cities, save energy, improve air quality, strengthen

quality of place and local economy, reduce storm water

runoff, improve social connections, help promote smart

growth, and create walkable communities. With such

tangible benefits directly available from a well-

managed urban forest, public funds should be pouring

into Adkins’ office. Unfortunately, they do not. As az-

central.com points out, the city designates funds for the

maintenance of established trees in its urban forest, but

8/17/2019 Tall Pots


not for the planting of new trees, or even for replace-

ment of lost trees.

In an email, Adkins writes he’s “familiar with the bene-

fits of tall pots” and “if the opportunity to utilize tall

pot material for a project was to arise, I am certainly in

favor of using the material.”

Given the ability of tall pot vegetation to thrive in arid

environments with minimal maintenance and limited

irrigation, the connection between Richard Adkins, the

forestry supervisor, and Harry Cooper, the flood con-

trol district’s landscape architect, should be an instant

win.

Adkins says in an email that public preference dramati-

cally favors top growth when selecting plants for resi-

dential or commercial use. Cooper, surrounded by his

nursery saplings, emphatically and disappointedly

agrees. Despite the demonstrable superiority of tall pot

trees in dry desert environments, these plants are not

mass- produced because there’s just not a market for

them. They are not as aesthetically pleasing as conven-

tionally grown plants when first transplanted.

While tall pot plant use in urban areas may remain a

challenge, their suitability for restoration projects is

being properly utilized. The Flood Control District’s

nursery maintains the ability to grow 8,500 trees at a

time and typically coordinates two to three restora-

tion efforts each year in conjunction with their flood

control construction projects.

At least with these efforts I may find myself once

again listening to frogs in the desert after a summer

storm. This time, however, thanks to tall pot plant

restoration, I will hopefully stroll through a grove of

trees, instead of standing staring at just one.

8/17/2019 Tall Pots


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Tall Pots