A “New” Technique for Arid Land Revegetation Projects TALL POT TREES A “New” Technique for Arid Land Revegetation Projects Welcome. The word “New” is in quotes because the idea of using tubes to grow seedlings has actually been around for quite some time in forestry and horticultural growing programs. Diana Stuart, Environmental Program Manager Flood Control District of Maricopa County

Where did this idea come from? European forestry departments have used tube-growing methods for several decades. Tube-grown horticultural plants have been used in the S/E United States for about 20 years. The Canadian Department of Forestry has also grown thousands of seedlings in tubes for at least 30 years.

In the mid-1980s, a researcher from San Diego State University began experimenting with using long tubes to grow arid land tree species. The idea started to catch on - - -

- - - In the late 1980s, Joshua Tree National Park began growing tall pot plants on a large-scale for revegetation projects in California; In the 1990s, the Arizona Game and Fish Department, and the Center for Native and Urban Wildlife at Scottsdale Community College began growing tall pot plants in Arizona.

Part of Joshua Tree N P Nursery Set Up The Joshua Tree National Park Tall Pot Nursery has the capacity for over 10,000 plants to be grown at one time. Part of Joshua Tree N P Nursery Set Up

Tall Pot Nursery – Scottsdale Community College Scottsdale Community College grows approximately 3000 plants at one time for the college’s Center for Native and Urban Wildlife projects. Tall Pot Nursery – Scottsdale Community College

Flood Control’s Tall Pot History In 2001, after seeing the success of using tall-pot grown trees at Arizona Game and Fish and Scottsdale Community College projects, Theresa Pinto started the District’s Tall Pot Nursery. On a “shoestring” the Nursery produced over 1000 trees in its first year.

The early Tall Pot Nursery with pots on the ground and an overhead irrigation system.

The Flood Control District has experimented with several irrigation system layouts, several germination techniques, and several planting methods. The FCD Tall Pot Nursery currently has the capacity for 6000 trees, and is growing 4000 this season. Just about everything will work! The keys are a good soil mix, and keeping the soil moist but not wet while the plants germinate and establish in the pots.

Why Tall Pots? Characteristics of Arid Land Trees: Most species have very long, fast-growing tap roots that reach to find soil moisture. Tap root length is several times height of above-ground stems. Foliage grows rapidly in hot weather but goes dormant when weather cools.

Anatomy of an Arid Land Tree

What Happens in a Typical Container? Tap roots grow around and around in bottom of container. Trees become root bound. When planted, root ball needs to be spread by hand. For a horticultural plant, being root bound in a pot prior to planting might not be as much of an issue since irrigation is almost always provided after planting. For an arid land plant that must “fend for itself” after planting, being root bound might mean failure to survive.

Tap root is spread, but still shallow. Tap root has to re-orient and grow toward soil moisture. If not irrigated, tree can become stressed or die before reaching soil moisture.

Typical Root-bound Plants

What Happens in a Tall Pot? Growing in a long tube allows the tap root and the ancillary roots to follow their natural tendency to reach for soil moisture. Even without irrigation, this slight head start is often the difference between tree survival and tree mortality.

Tap Root From A Cut-Open Pot At Scottsdale Community College If the tubes are raised on a platform or set in racks, roots can be allowed to grow out the bottom, or may be cut if planting is delayed. We recommend planting tall pots when they are about 1 to 1-1/2 years old, or when they reach 12-24 inches in height, however, they will do fine in the pots for longer periods of time. Tap Root From A Cut-Open Pot At Scottsdale Community College

What is a “Tall Pot”? Tall Pots are long, narrow tubes with wire mesh at the bottom to hold in soil. The District uses 10-foot lengths of #D2729 PVC, 6-inches in diameter, cut into 4 each 30-inch long tubes. Squares of wire mesh hardware cloth are put in the bottom to hold in the soil.

Tall Pot Tubes Ready for Use in FCD Nursery The wire mesh hardware cloth is held in place by two cross wires run through small holes drilled in the bottom of each pot. Tall Pot Tubes Ready for Use in FCD Nursery

Yes, we have specs - - - The Flood Control District has produced a full set of specifications for tall pot tube fabrication, rack fabrication, soil mixture, and planting methods. These are available for both growers and end-users upon request. A tall pot nursery can be really fancy, or really plain. As noted before, the arid land species we work with don’t seem to care about looks, just the right soil mix and the right watering program.

Typical Tall Pot Cross-section

Planting Tall Pot Trees To provide root/soil moisture contact, planting hole is: narrow diameter and as deep as pot, augured or drilled with post hole digger, filled with water before planting. In very sandy soils, skip the pre-watering of the hole and just slurry in the back-fill when planting.

Simple.

Or fancy. Step by step instructions with drawings are included in the specs.

What about irrigation? With irrigation, arid land trees do best if planted in the early spring to take advantage of their peak growing period during the warm/hot months. Without irrigation, arid land trees do best if planted in fall or early winter - - -

Roots continue to grow even when above-ground growth slows; Trees get established without the stress of summer heat; and Winter rains provide just enough water - - - USUALLY. Even without an irrigation system, water is used during planting. The holes are filled with water and allowed to drain before planting the tall pot plant. Back-filling of the hole is done with water to make an air-tight slurry as the tube is being lifted up out of the hole over the plant.

But there’s a trick: The Flood Control District specifies planting with DriWater® at our project sites when irrigation is not feasible. DriWater® is water blended with a cellulose gum and gel-based matrix. Soil organisms consume and metabolize DriWater® and the by-product is free water.

It slowly delivers water to the root zone for up to 90 days; DriWater® gives plants a steady moisture boost as they establish, regardless of seasonal rains; It slowly delivers water to the root zone for up to 90 days; The containers are biodegradable so they can be left in place. It is important to note that DriWater® is not the same as a polymer-based product. Those tend to act as a sponge and actually compete with the soil to grab soil moisture.

Installing DriWater® DriWater® is available from several catalogs or from the distributor, Rain Bird, Inc. Currently there is only one manufacturer of the product.

Protection methods Seedlings and saplings can be protected in several ways. There are advantages to each method: Chicken wire cages Biodegradable protectors Liquid Fence® spray Chicken wire cages provide the most protection from herbivory, but they must be properly anchored, usually with rebar, and then must be removed a year later when the plants are established. Biodegradable protectors should be put on in the nursery after the plants germinate. They are anchored with bamboo stakes. When the plants are planted, care must be taken to bury the bottom of the protector below grade to prevent small rodent entry and wind milling. Unfortunately, biodegradable protectors do not prevent herbivory from deer and javelina which can reach over the top to browse. They tend to restrict a tree from bushing out at first, but they will biodegrade after about 1-1/2 to 2 years, allowing the tree to proceed growing normally. Liquid Fence® is a garlic-based non-toxic spray that comes in several formulations. We have used the deer and rabbit version with good success at our McMicken Dam project. The disadvantage is that it needs to be reapplied occasionally, especially after a heavy rain event, but it is relatively inexpensive, and a little goes a long way.

Biodegradable protectors in the Nursery and at a project sight.

Some Tall Pot Success Stories: In the South to grow more productive Pawpaws. Over 1300 Tall Pots with 98% survivability used for a highway project near Santa Fe, NM. Revegetation project in Death Valley N.P. with 87% survivability.

Several hundred Tall Pot trees used to revegetate Red Rock Canyon State Park in California after the filming of Jurassic Park! More than 10,000 Tall Pot trees used by Cal Trans (California DOT). The revegetation of Cienega Creek in Pima County by Pima FCD. And - - - ?

FCD Chandler Mitigation Site During Planting in 2004, and July, 2005

McMicken Dam Project Site Before Revegetation – Summer 2005 Those of you willing to take the tour today will see how this site looks today. The hydroseeding didn’t take, but the Tall Pot trees did, even after a winter with no rain, and a searing summer with little monsoon rain. McMicken Dam Project Site Before Revegetation – Summer 2005

Summary of Why Using Tall Pots is a Good Policy: Substantial cost savings over installing irrigation systems or frequent use of water trucks; Higher survivability in harsh environments. Irrigation systems can run upwards of $25,000. per acre in revegetation projects. If no water source is available to tap into, frequent visits by watering trucks can also be expensive. Tall Pot plants installed with DriWater® can be left alone to establish on their own if necessary. Works with the natural rooting tendencies of arid land species.

Acknowledgements: Theresa Pinto, Project Manager, Planning Branch, Flood Control District Ben Ganados, Ecology Technician, Planning Branch, Flood Control District Jean Graham, Biologist, Native Tree Nursery, Joshua Tree National Park Roy Barnes, Director, Center for Native and Urban Wildlife, Scottsdale Community College Russ Haughey, Habitat Program Manager, Arizona Game and Fish Department

Questions? For Tall Pot technical questions: Diana Stuart 602.506.4766 dms@mail.maricopa.gov For Planting or Nursery operations: Ben Ganados 602.506.8612 bag@mail.maricopa.gov