GARDENER'S MAILBAG

Hybrid oaks are likely hand-selected live oaks

By Neil Sperry | Published Wednesday, August 6, 2014

Dear Neil: More than 30 years ago, we purchased what the nursery called a “hybrid” oak. It looks like a live oak. Do you have any idea what it would be a hybrid of?

Oaks are pollinated by the wind. (Think about the golden dust that accumulates on your car for a week or so each spring.)

By that token, they are all hybrids – you never know the source of the pollen that lands on the female flower parts. However, of our common oaks, only live oaks will vary considerably from one tree to the next.

Trying to minimize that variation, several large wholesale nurseries over the years have carefully selected their trees to have desirable and similar attributes from one tree to the next. They labeled them by trademarked names, and most referred to them as “hybrid” oaks. In all of those cases, they were still just hand-selected live oaks (Quercus virginiana).

Dear Neil: How can I eliminate tree-of-heaven sprouts that are coming up from a neighbor’s tree, also from two stumps left behind when I removed trees a year ago?

The way to kill sprouts that are coming from a stump is to drill into the stump and pour a broadleafed weedkiller (containing 2,4-D) into the hole(s). Let it soak into the wood, and it will be carried out to the sprouts.

As for the neighbor’s tree, the only way to stop its sprouts from invading your yard would be to put in a root barrier 18 to 20 inches deep along the property line.

Dear Neil: We have three tall Italian cypress trees that are turning brown from the bottoms to the tops. We have sprayed them for mites and we continue to water them, but they’re not getting any better. What else could be going on?

I think your assessment of spider mites was correct. If the problem is continuing, before you spray anything else, take a browning (not dead) twig and thump it over white paper. You should be able to see the mites crawling around on the paper. They are quite tiny – you could probably put 20 of them shoulder-to-shoulder on the head of a pin.

Spray with a product labeled for spider mites, and use high pressure to force it through the entire plant. It may take months for new needles to be produced.

Dear Neil: What would cause scattered boxwoods in a foundation planting to die? I see no lacebugs, and they survived the winter just fine. They’ve been in this spot successfully for 15 years, and I’d hate to lose them. I don’t understand why they are dying.

I would be very suspicious of nematodes in the soil. This is the way they will kill boxwoods. One plant will die, then the two on either side will succumb.

Nematodes are soil-borne microscopic worms that feed on plants’ roots, usually resulting in small galls on the roots. The Texas Plant Clinic at Texas A&M can do a soil test to see if they are present.

There is no good control for them, and when they begin to take a planting down, all you can do is switch over to something similar that isn’t susceptible. Owing to its similar appearance, the best choice is usually dwarf yaupon holly. They are not bothered by the pests.

Dear Neil: Why are runners on my St. Augustine lifting up above the rest of the lawn? Do I need to be concerned?

It is not of concern. Turf people have told me that there is a very minor fungus that causes loss of the small roots on a few runners.

I’ve had this in my own St. Augustine lawn for 40 years. I just mow them off and forget about them.

Dear Neil: We have purchased some property west of Houston and are wondering what shade trees would be best there. We would like to plant some this year.

October is the best month to plant them. Oaks are always good, including live oak, bur oak, chinquapin oak and Shumard red oak.

Pecans are very good and large. Choose varieties recommended for your specific area.

Cedar elms and magnolias are equally good, and Chinese pistachios are, too, if you don’t mind a non-native tree. Let a local independent retail nurseryman offer input as well.

Dear Neil: We purchased two Texas mountain laurels two years ago. They have survived, but not thrived. We get seedpods but no flowers. Any suggestions?

If you have seedpods, you had to have had flowers. Texas mountain laurels grow best when they’re in moist, well-draining soils. Although they’re drought-tolerant, allowing them to stay dry slows their rate of growth.

Dear Neil: I have tried two different Crimson Queen Japanese maples, and both have struggled in the same location. I’ve been told the spot gets ample light. What would cause them to lose leaves starting almost immediately?

Japanese maples need almost total shade, so any comment about “ample light” makes me worry just a little. I’ve had a Crimson Queen maple in a pot for 10 or 12 years. It has had some leaf drop along the way, and I could always attribute it to its having gotten too dry.

If you’re sure this spot isn’t too hot and sunny, you could always try a different variety, although most grow larger than Crimson Queen.

Have a question you’d like Neil to consider? Mail it to him in care of the Wise County Messenger, P.O. Box 149, Decatur, TX 76234 or email him at mailbag@sperrygardens.com. Neil regrets that he cannot reply to questions individually.

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