Neil Sperry's Mailbag

DEAR NEIL: I have a fungus in my St. Augustine. I tried several products, then hired a lawn care company. They sprayed four times and the fungus is still there. A nurseryman recommended a fungicide, but it says on its label that it only controls it -- that it won't eliminate the fungus. What can I do?

Actually, there are several disease problems with St. Augustine (as there are with most plants). Most of them will wash or blow back into the yard at their favored time each year. In other words, no fungicide is going to guarantee permanent elimination of a disease on any plant. Find out which specific disease is attacking your St. Augustine (take-all patch is common in the spring, gray leaf spot in the summer and brown patch in the fall), then follow the appropriate steps to stop it for that season.

DEAR NEIL: I have five Gulfstream nandinas. It looks like they are dying. The leaves have all dried up and the stems are brittle. What could have caused that?

I get notes relating to various parts of Texas. Soil conditions and weather will vary a great deal. For the record, Gulfstream nandinas show serious problems with iron deficiency in really alkaline soils. Actually, all nandinas have that same potential, but Gulfstream tends to become stemmy, yellowed and clumpy looking. Sometimes you can dig the clumps out almost as you would a clump of perennials, cut the canes back to within 3 or 4 inches of the ground to encourage regrowth, then rework the soil completely, mixing in generous amounts of new organic matter such as peat, compost and pine bark mulch. On the other hand, you might prefer simply to start with new plants, maybe even of a different species. In my garden I don't have a serious alkalinity problem, but I've switched back to the second tallest nandina, one called Compacta. It grows to about 40 inches tall and I've never had any of this problem with it. Gardeners with neutral or acidic soils have far fewer of these issues.

I plant them in pots and leave them outside all spring until it turns hot, then put them down in our basement (unusual for Texas) where it's cooler until fall, will I be able to raise rhubarb here? The thing I don't understand is that it also gets hot in Iowa.

I'm going to try to explain why bluegrass, lilacs and rhubarb struggle in Texas, and I'm going to use a bank account example. Let's say that you start with $100. On good days you put in $10, but on bad days you take out $15. If you have enough bad days and not enough good days to balance, your account will eventually shut down. Now, switching to plants: if you start the summer with a healthy, vigorous rhubarb plant that is busily storing food from each days' sunlight, it will be producing slightly more food (sugars) than it needs to sustain its own life. However, when temperatures move past its preferred level and stay there for 3 or 4 months at a time, its "bank account" of stored sugars is exhausted. The plant literally cannot keep pace. We have probably 100 days at or near 100 degrees here.

Iowa has far, far fewer. Or, to put it in one other set of terms, with winter cold-hardiness temperatures, each species pretty much has one temperature below which that species cannot survive. With summer high temperatures, it's more the length and frequency of high temperatures than it is the actual temperature reached. Long answer, but I'm trying to save you a ton of trouble that will never work.

DEAR NEIL: I have enclosed leaves and a photo from my oak tree. It has a disease. What should I do for it?

The leaves were pretty mushy and moldy by the time they arrived, but they didn't look like oak leaves - more like a mulberry or elm due to their large size, oval shape and notched leaf margins. To your point, you probably have seen a fungal leaf spot this summer and fall due to the prolonged wet weather of late spring and summer. There is absolutely nothing you would need to do for such a problem at this time.

Have a question you'd like Neil to consider? Mail it to him in care of this newspaper or e-mail him at mailbag@sperry-gardens.com. Neil regrets that he cannot reply to questions individually.

Neil Sperry
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