>Growing my garden knowledge

>I’ve mentioned before how grateful I am to have taken the Master Gardening class last year. It is so fascinating to take a casual hobby and really intensely focus on growing your knowledge in the area and finding out whether what you knew before is factual or urban garden legend. I find that working at the Master Gardeners phone desk answering calls from the public on gardening helps me continue to develop my knowledge base and hone my skills. I still feel very much a beginner but it is wonderful being surrounded by those who have been involved for many more years.

Austin bloggers have commented a lot about our unusually wet year this year. One of the issues we have been getting a lot of calls on this year is Oak Leaf Drop- not to be confused with Oak Wilt which is terrifying to have happen to a prize large oak tree. Here is some information should any of you be interested in Oak Leaf Drop and how the wet weather has affected trees.

Abundant rains have continued to fall across most areas of Texas all summer and into the early fall. These rains coupled with abundant humidity from the Gulf have extended the early summer symptomatic outbreaks of leaf disease in oaks, specifically live oaks, this year. Oaks are still experiencing significant leaf drop (defoliation) throughout their canopies and especially on the lower half of the tree. Affected trees look very thin and sickly from a distance. Their fallen leaves on the ground appear spotted or mottled with blotches colored yellow, brown, and light-green. However, the live oaks are still putting on a sustained growth flush starting in mid August and extending into October. This can be seen as long twig extensions (candling) at the outer edge of the canopies.

As we cautioned in early summer, this defoliation is not oak wilt. This problem is only confined to the leaf tissues. Branches remain alive and viable for new leaves to form still this fall or next spring. The trees are not dying. Fungicides are ineffective as infection occurred earlier in the year. Raking up and disposing of the fallen leaves on the ground is a good strategy to remove the local inoculum. This defoliation is a natural occurrence and something that typically happens to the oaks in high rainfall years. This year is different since the rains have continued to come since late winter and leaf disease conditions and subsequent leaf defoliations have persisted all summer.

Again, this is not oak wilt. Oak wilt leaf symptoms are completely different. Also a pattern of mortality in the stand of trees over time is not apparent, i.e. an infection center radiating out over the landscape for several years. The oaks will recover and put on new leaves. This year’s excellent growing conditions will carry over into next year’s growth and the oaks of Texas will continue to grow and provide us with their many benefits.


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