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Tuesday - August 28, 2007

From: Austin, TX
Region: Southwest
Topic: Non-Natives, Diseases and Disorders, Trees
Title: Oak leaf fall causing ivy damage
Answered by: Barbara Medford


I read the A/Q in the Austin American-Statesman Saturday, August 25, regarding the leaves falling now from the live oaks. I am experiencing the same thing, but it is the leaves of my post oaks that are falling much too soon. The damage is that my English ivy is dying. Please advise.


Okay, we now come to the point about use of native plants in your landscape. Quercus stellata (post oak) is a native Texas oak, very drought resistant, with large leaves providing shade in the summer garden. They are seldom seen in nurseries, because they are very difficult to transplant; therefore, unless you had the post oak on land where your house is built, you probably wouldn't have it at all. Quercus stellata takes care of its own propagation. Many gardeners, as you have done, use mature native oaks to give shade and shelter to shade-loving ground covers.

Hedera helix, English ivy, is a native of most of Europe and southwest Asia. This summer, in Central Texas, for two months we had a climate like the regions where English ivy originated, cool, cloudy, and rainy. The post oak, unused to such conditions, dropped some leaves in protest. Then, summer came back to Central Texas, along with normal heat and bright sunshine, and the English ivy had lost some of its protection. It is suffering from something like sunburn, as the large, dark leaves are suddenly getting much more sun than they customarily do. Under normal circumstances, by the time the post oak dropped its leaves in the fall, the weather would be cooler, the sun lower, rain more frequent and the English ivy would be fine. The native post oak will easily survive this sudden change, because it IS a native, and its species has seen this kind of trick played by Texas weather before. We suspect the English ivy will also survive; even though it is not a native. English ivy, in fact, can be pretty aggressive in shady landscapes, and in the Pacific Northwest where the climate is similar to that in the native home of Hedera helix, it is often considered invasive. A little more water and perhaps trimming back long runners of the ivy that have browned or lost leaves should tide it over.

Quercus stellata




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