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Wednesday - September 01, 2010

From: Austin, TX
Region: Southwest
Topic: Invasive Plants, Non-Natives, Trees
Title: What about Asian Jasmine and scrub oaks?
Answered by: Jimmy Mills


Dear Mr. Smarty Plants, I have several clusters of native scrub oaks in my yard. I planted Asian jasmine under them many years ago. The trees look fine, but an arborist has told me that the Asian jasmine is suffocating them, like when you put too much soil around them. So, what should I have put underneath the trees? Is it best to leave the area under them bare soil? In nature, they can have understory plants including vines underneath them. So, why is the jasmine not good? Is the vine just too thick? Thanks for your thoughts!


Lets start with the Jasmine part of the question. Asian Jasmine (Trachelospermum asiaticum)  is an evergreen ground cover for sun and shade. As its name suggests, it is non-native although it is widely used by landscapers because of its vigorous growth once it becomes established. This agressive growth can become a problem when it invades flower beds, climbs trees and shrubs, and even grows into houses. This link to Dave's garden has some comments from both admirers and detractors of the plant.

I think your arborist's concern may be about the competition between the oaks and the jasmine. The jasmine is competing with the oak tree for water, minerals, and oxygen. As the jasmine becomes more dense, it can deprive the oaks feeder roots near the surface of crucial oxygen, thus "suffocating" the trees. The oak trees have roots that extend out to the drip line and beyond; if the jasmine bed doesn't extend that far, the problem is lessened.

So what are the alternatives to Asian Jasmine and bare soil? One possibility is to mulch under the trees with decorative mulch, or do hardscaping with flag stones and gravel. To find plants to use in this situation, go to our Native Plants Database and scroll down to Recommended Species and click on the Cenreal Texas portion of the map. This will bring up a list of 155 commercially available native plant species suitable for planned landscapes in Central Texas. Clicking on the name of each plant will take you to its NPIN page that describes the plant and tells about its growth characteristics and requirements. Next go to the Narrow Your Search box and make these selections: Select Texas under State, Herb under General Appearance, and Perrenial under Lifespan. Check Part shade under Light Requirement, Moist under Soil Moisture, and click the Narrow Your Search button. Your list has been narrowed down to 14 species. You can alter your list by repeating the process and making differet selections e.g. choose Shrub instead of Herb under General Appearance etc. This answer to a previous question similar to yours provides some possibilities for plants under oak trees.


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