Planter Design for Desert Species

17 years ago

I am an architect at a firm in Phoenix, AZ. I am working on a commercial project in Scottsdale, AZ that has several large planters sitting on top of a parking garage. The planters are made of concrete and contain around 4-5 feet of soil. My team and I have worked out most of the issues surrounding drainage etc but we are concerned that the trees will tip over in high winds due to the shallowness of the planters. As you all know desert species typically send out a deep tap root for support but that will not be possible in the planters. Do any of you know of any systems for securing the trees roots in the planter. Our thought was perhaps some sort of metal or plastic mesh buried in the soil but secured to the planter so that the roots could grow around and cling to it for support. If any of you have experience with this or any other methods or products for securing tree roots I would appreciate your help.

-J

P.S. This would be in addition to standard tree staking which we would like to remove after 2-3 years.

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Comments (5)

The_Mohave__Kid
17 years ago
I don't believe the depth of your planters will be the limiting factor in anchoring your trees in the planter. More important is the available surface area of the raised beds and your ability to efficiently irrigate the anticipated root zone that will support the tree.

A good product we have started to use in our park system that would really work well in your situation is the "Netafin" drip line. This drip line can be set up in a grid pattern and installed very easily in a raised bed and would provide a high degree of irrigation uniformity giving you the potential to grow a substansial root system.

We work with many desert trees in windy conditions and under cultivation find most of the roots in no more then three feet of soil and mostly two feet of soil. A more problematic situation developes when initial irrigation is limited to the existing root zone at planting time without enough irrigation in the "anticipated" or potential root zone resulting in a root mass filling the original hole and not spreading out around the tree. The Netafin system in our park projects so far shows a great deal of promise in this regard since it irrigates a sizeable area below the tree with no need to make future renovations to the system.

If you gave some thought to your soil texture and mixed in a gravel mix for structure I don't think you would need an additional "artificial" anchoring system.

Keep in mind you can't grow trees in a shoe box. The depth of your beds is fine it's the total area that is what you need to increase .. perhaps ( I don't know what it is ? ). I also think if you need to stake trees for two to three years someting is not right somewhere ??

I'd be interested in hearing more about your project.

Good Day ...
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gardengal48 (PNW Z8/9)
17 years ago
Plants develop tap roots in response to a search for water - provide adequate moisture in the soil and little or no tap root develops. Mohave is correct in stating that the bulk of most tree's root systems will be in the top 24" of the soil and most of the fine feeder roots will reside in the top 12". Spread is more critical than depth.

You may be interested in examining container and rooftop garden planting techniques in other arid climates. The use of perlite as a significant component of the potting medium has provided some rather amazing, lightweight and moisture retentive plantings in places like Israel, India and areas surrounding the Mediterranean. It is also used extensively in green or living roof applications throughout Europe with great success. As usual, we Americans are a bit behind the boat on this one.

Here is a link that might be useful: Israeli roof top and container plantings
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nandina
17 years ago
The use of perlite as a planting medium is known in this country. However, it requires a dedicated (not fly-by-night) landscape maintenance company familiar with its special growing needs for healthy plant growth.

I do not like to stake trees. Much prefer to plant younger ones and let them adjust to the wind conditions. That is not always possible in the world of commercial landscape.

Are the containers of a shape that it would be possible to place one or two immovable, decorative large rocks on each? The additional weight should hold the trees in place and retard water evaporation. This is a parking garage designed for heavy loads.
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mohavemaria
17 years ago
{{gwi:17544}}
Is this what you want to avoid? We were out for pizza when the wind got gusty, no tornados in Las Vegas, and when we went to a large furniture store afterwords we found all the chilean mesquite trees knocked over in the parking lot. Other trees in the area were fine. These were not in a planter so they could send deep tap roots but fell because of improper culture, too much water, too close to the trunk.

Your idea of a type of support network built into the planter sounds good to me but even better IMHO would be to use a tree with a lower wind profile. Something with a sparse canopy that lets the wind through like a desert museum palo verde maintained by an arborist who can keep it thinned even more to match the severly constricted root mass of a planter.

It's great that you are thinking long term, so many don't and that's why we see so many big trees in tight spots and knocked over by wind gusts here.

Good Luck, Maria
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inkognito
17 years ago
You might want to have a look at 'Duckbill' anchors as a possible solution. Thanks for that picture Maria. The closest tree has roots that are girdling (strangling) the tree you will also note some strange things about the supporting stake. I would place a bet, this being Las Vegas,that the available soil is the same depth as that uprooted root.
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Planter Design for Desert Species

Comments (5)

The_Mohave__Kid

gardengal48 (PNW Z8/9)

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nandina

mohavemaria

inkognito

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