Tuesday, February 17, 2015

Drought Survivability Study: Testing limits of landscape plants

Just how much water is required to keep landscapes looking good through a drought in Central Texas?  Or is the question really "good enough" during such times?  These are questions our region has been grappling with during several years of extreme drought conditions.  The challenge is more than lack of rain since our growing population increases the demand for water, while landscapes are a major drain on water resources.

Last week my friend Melody and I traveled down to the Drought Simulator southeast of town to learn more about a new research project headed by Dr. Calvin Finch of Texas A&M's Institute of Renewable Natural Resources.  This Drought Survivability Study will enable researchers to document the performance of 100 of our most popular landscape plants under different drought conditions.  The study is sponsored jointly by the San Antonio Water System (SAWS), the cities of Austin and Georgetown, and the San Antonio River Authority (SARA), as well as Texas A&M.

Dr. Finch opened the presentation with an overview of the study.  I was particularly heartened to hear that Dr. Finch, horticulturist and gardener, is placing importance on keeping our landscapes looking good during drought while conserving water.  According to materials received at the meeting, currently available research indicates we may be overwatering our plants.



Christopher Charles of Austin Water (at table) spoke about the importance of having scientific data to reference when implementing standards for developers and landscapers.  Also in the photo is Tracy Hobson Lehmann of the San Antonio Express-News and Lee Marlowe from San Antonio River Authority.


Input from nurseries and landscapers was used to select 100 different plants for the test, generally according to local popularity among consumers.  Although San Antonio, Austin and Georgetown (north of Austin) span different planting zones, the selected plants are common to all three areas.  Trees, shrubs, perennials, vines and grasses are included in the study which uses 1,600 plants (16 of each of the 100 varieties) divided among four grids.  In this photo you can see the Sago Palms are repeated across the other side of the grid.



After initial watering in to get the plants established, the plants will receive varying amounts of hydration, including some which receive zero water.  In the event of rain a motorized metal roof on tracks will automatically move over the plants designated to receive no water at all during the study.  These plants will only be hydrated after the summer is over to see which plants revitalize.  Reclaimed water supplied by SAWS will be used during the study.


All the plants will receive the same amount of water for the first 90 days to get them established then watering will be varied based on percentage of "potential evapotranspiration to determine the actual amount of water they need to survive."  Potential evapotranspiration or PET is a new phrase to me so it was interesting to learn just how scientists determine the amount of water each plant needs.  It's an estimate of the "amount of water moving through the plant and from the soil based on the weather conditions" according to handout we received at the presentation.  We have had a particularly good winter for rain and this brings to mind a question on how water will be controlled to the other three grids if we have above-average rainfall.


Each plant will have drip irrigation to closely control water application.  Chile Pequin, a native chile plant, sports bright red fruit throughout the year.



After a year of observation and data gathering, the best performers will be part of two recommended landscape plans for our region.


The City of Georgetown will have a second site running a concurrent test.  The 5,000 square feet Drought Simulator structure was previously used for a turf grass study.  The area to the right is under the structure when not in use and will not be planted.


After our walking tour, Melody (in the blue jacket) chatted with Tracy from the Express-News about upcoming garden events in San Antonio.  On the right, representatives from the City of Georgetown, San Antonio Water System, and Texas A&M discuss the project.


I'll be following the project over the next year and look forward to posting the progress and results as information becomes available.  More details are available at Texas Agrilife Today.

29 comments:

  1. Really interesting...thank you!

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    1. I'll try to keep up my interest even in August when it will be incredibly hot out there.

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  2. Such a great initiative that will pave the way in achieving great landscaping without being a burden to water sources. I'm very curious now which plants will do well.

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    1. It will be important to have measured results along with garden experience. I attended another seminar yesterday on the subject of watering plants. It does seem that as little water as I use now I just might be able to cut back some more.

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  3. I look forward to hearing the results of this test. Cool stuff!

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    1. And you live in rainy Tacoma!

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  4. Take a great big parasol in August, Shirley. I'm so glad you reported on this plant trial. I'd not heard about it. I'll be eager to hear the results.

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    1. I'm thinking a golf umbrella is a good idea. With all this interest I'll probably trek out there about every 90 days or so.

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  5. Ah - this might put the end to an ongoing "discussion" between the Hub and I about supplemental watering in our xeric areas. He sees plants reacting in natural ways to heat and light (drooping, leaves closing up, etc.) and wants to head out with watering cans. It will be nice not only to have a list of the very best of the best plants to choose, but also some local scientific data on how much water IS enough. Thanks for this!

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    1. I think this question is the key for home gardeners. How long can we let them go and will they recover? I've noticed that some plants wilt in August heat even when the soil is still damp.

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  6. This is just what we need. A sound study and data on how much water to give each plant instead of blanket watering.

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    1. I'm most interested to find out if I can relax on the August watering.

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  7. Shirley, I am so glad you posted about this. I am very interested in learning which plants make the cut! What an important study, and a very useful one. I have several areas where I can not feasibly add irrigation, and this may just allow me to have a garden where I currently have none. These are the type of plants I want to suggest to DD for her landscaping. Looking forward to hearing more.

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    1. While it is our utilities and public institutions funding this study, it seems to have connected with those of us who simply love to grow plants but don't want to water all day in August. I think I'm committed to following through on this. Your daughter lives in the SA area now if I remember this correctly so this will be very helpful to you as you advise her.

      Good to hear from you Holley, I've missed your blog.

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  8. I read about this last week- super exciting project! I know my stuff lives without supp. water...I'm excited for the skeptics to see that it is possible with many plants (as long as the gardener is okay with lush and not so lush years)...I am!

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    1. One of the most important elements of this will be to understand the wilt and recovery tolerance of my plants. I don't mind the wilt as long as they recover in time.

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  9. I'm glad to hear that there are people doing this kind of study. I hope there are similar studies being conducted in California as well, although I haven't heard of any. In any case, I'll be very interested to hear the results of yours.

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    1. The drought info should be helpful even though we get a good bit hotter and colder than you do on your beautiful Pacific hillside perch. We grow some of the same plants and you have similar interest in learning how to landscape for severe drought.

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  10. Fascinating. I love to visit these test gardens to see how plants really perform in various situations. There's a University of Wisconsin test garden in Madison that plants various species and cultivars side-by-side and publishes online research that the public can check to see how each plant performed during the season. It's fascinating to see which plants the pollinators prefer, too. It can be eye-opening to a gardener. Great post! I'll be curious to read more about this Texas project through your posts.

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    1. I'll have to check that out. I have seen some posts on the gardens there. We don't get quite as cold but the science is always interesting.

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  11. What a great study! Our region receives significantly more rain than you do but we all still need improved guidelines. Perhaps better alternatives to water hogging non-natives can be promoted at local garden centers.

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    1. Virginia is lawn country and that means lots of watering in the summer! Even when surrounded by rivers as you are it's a good idea to conserve water and cut down on the costs of supplying that water.

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  12. It isn't just the availability of water that is the problem in a drought. Even a slight increase in temperature can make or break a plant's survival. It is a happy coincidence to see this post as I -just- finished reading A Great Aridness: Climate Change and the Future of the American Southwest by William deBuys. I highly recommend it for anyone who wants to learn more about how drought affects plants.

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  13. I saw this on Channel 12 News about 2 weeks ago. Didn't know it was open to the public. Did they by chance list the plants that are being tested? I know it sounds naïve, but every time I see all that snow up north I wish they had a pipeline for that to Texas. We have enough oil! Keep up the good reporting.

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    1. There's a link to the plant list in this article from the Rivard Report. Scroll down to find it.

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  14. Thanks for reporting on this important project! Like the others, I'll be very interested to see the results.

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  15. With the water shortages and hotter temperatures this is a really interesting study. It may not pertain to my area much since it's colder here so the plants may not be hardy enough, but we don't have any rainfall all summer so it's an imposed drought even though we get lots of water in the wet season.

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  16. What a great study...I look forward to your updates. People are often shocked to know I do not water my garden. My veg garden yes if we have not had much rain in so many days...containers if they are dry, but the bulk of the garden is now a majority of natives. They are established and seem to thrive on the water we get from snow and rain as does the lawn. I do think many people all over overwater their gardens....even those of us not in a drought need to conserve water.

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  17. Great post, lovely series of photos.

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