Neil Sperry's Mailbag

DEAR NEIL: I have an ornamental cherry that has struggled. I pruned away part of one branch and noticed that it was black just under the thin bark all the way out on the branch. Because losing that partial branch ruined the tree's symmetry I removed the rest of it. Just wondering, for future reference, what the black coloring was.

It was probably secondary to the death of the tree's branch. Fungal organisms move into wood as it begins to decay. If you removed all the dead wood and pruned back into healthy growth that particular problem has hopefully been solved.

DEAR NEIL: Several of our friends in the Hill Country have flowery senna trees that are dying. They are all 2 to 3 years old and were doing great.

Suddenly they started losing leaves and ultimately died. What might have caused it?

That's a cousin plant to our common candle trees. I've grown both and have never had anything other than cold weather kill either one of them. Candle trees, of course, are annuals. Flowery senna is a woody shrub that is hardy into the teens (Zone 8). Obviously cold didn't kill them. It might have been poor drainage or, in alkaline soils, there might be a chance they would suffer from cotton root rot but that's not terribly likely. Without more clues of symptoms it's hard to diagnose a plant's problems just from the fact that it died.

DEAR NEIL: We moved here from Virginia last year. I try to use plants that are recommended for this area. My plants did well last year during the drought, but this year everything has a yellowish cast. Are they lacking nutrients? Even my lantanas look terrible.

You have diagnosed your problem perfectly. Nitrogen has been greatly depleted by the ongoing heavy rains that have hit most of Texas this spring and summer. It's time to replenish the supply by using a high-nitrogen or even an all-nitrogen plant food. The sole exception would be with St.

Augustine that has been struck by gray leaf spot. Wait until September to feed it. Of course, keep your eyes open for other plants that have been hurt by continuously waterlogged soils and attacks of fungal diseases brought on by the high humidities.

DEAR NEIL: How can I kill poison ivy on a tree trunk?

First of all, know that all parts of poison ivy can cause the allergic reaction and know that every human, at some point or another, is susceptible. Never assume that you are immune. Wear washable gloves, long pants and a long-sleeved shirt. Cut the large trunks that ascend the trunk near the ground with a long-handled axe. Watch out for the spewing oil from the wood of the vine. Make a second cut on each poison ivy trunk about 18 inches above the first cut then use the head of the axe to pry and pop the 18-inch segment loose from the trunk. The top of the vine will die. Leave it in place until it dries and falls to the ground in the next year or two.

However, you'll want to treat the root stump of the vine with a broadleafed weedkiller. Use the axe to macerate the stump slightly, then carefully pour the herbicide onto the roughened surface at full strength. Do not allow it to run onto the ground. It will soak into the wood of the stump and kill it, preventing resprouting in the process.

DEAR NEIL: How can I keep squirrels from getting my small tomato fruit? I've tried peppermint oil spray, and I have put an electric fence and they just jump it.

Obviously you'll need some type of enclosure they cannot penetrate. It might be that bird fabric (supple, looks like plasticized chicken wire) might help, or your could construct lightweight panels out of actual chicken wire. They could easily be put in place and removed as needed. Humane traps might work, but most of us have ample supplies of additional squirrels nearby to fill the voids.



DEAR NEIL: What would keep a 2-year-old crinum lily from blooming? We have them 15 to 18 inches apart and the middle one has bloomed several times but not the other two.

That's difficult to diagnose without seeing them, however I will say that that is pretty close for most crinums. They tend to grow large. Maybe the middle one has better placement in terms of light and moisture. Try replanting the other two this fall. Even if you just move them 12 or 18 inches farther away it will give you the chance to redo their planting soil at the same time.



DEAR NEIL: How can I eliminate crabgrass in my lawn? I've had a small patch of it in the past but this year it is rampant. Why would there be so much now?

Crabgrass is an annual grassy weed. It germinates in early spring, grows and begins producing seed by early summer and continues until frost. Just to be sure we're talking about the same grass, it is light-to-medium green in color. It produces short runners to 8 to 12 inches long. The seed heads are borne above the grass and they somewhat resemble helicopter rotors. If that's what you're seeing it probably got a toehold during the drought and has flourished with this year's rains. Prevent its germination by applying pre-emergent herbicide granules a week or so before your average last killing freeze date and again 3 months later. You can eliminate existing crabgrass and other grasses in bermuda turf by spraying with MSMA. Do not use MSMA in other types of grasses as it will kill them.



DEAR NEIL: A year before my beloved stepfather died he gave me a mulberry tree seedling from Marietta, GA. My mother made heavenly jam from its parent tree. My tree is now 8 years old and has never produced a single fruit. Will it ever do so? I have it growing at the edge of a woodland. It has grown well, but I am so hopeful to have fruit.

Be patient. It's not uncommon for fruit trees that have been grown from seed to take that long to start producing. They invest most of their early years simply in growing to their mature size and form. If you think about it, animals operate about the same way. One of the next several springs it will start producing and it will never stop again. I have yet to see a seedling mulberry tree that didn't eventually have fruit. Of course, it will grow best in full or nearly full sunlight. Hopefully your woodland won't be an issue.



DEAR NEIL: You created a stir in our house with your comments that this year's heavy rains have depleted our soils of nitrogen. Doesn't lightning add nitrogen back to the soil?

Plants require many nutrients to grow vigorously and remain healthy. None is used in greater quantity than nitrogen. Whether it's from organic or inorganic sources, nitrogen eventually becomes water-soluble. In fact, that's the way plants take it into their root systems - in water solution.

When heavy rains come they leach much of that available nitrogen out of the plants' root zones. We can plant legumes with their nitrogen-fixing bacteria, and thunderstorms do have some effect, but the elephant's share of the work comes from the regular addition of nitrogen fertilizers.



DEAR NEIL: I recently read about using NAA (naphthalene acetic acid) on crape myrtle sprouts at the base of the bush to control sprout regrowth. Do you have any experience with this chemical and procedure for crape myrtles?

If so, where would I obtain NAA and what would be the directions for its use?

The University of Georgia's Center for Urban Agriculture has the most conspicuous mention of this I could find online. To my knowledge it is not a common practice beyond research horticulture. On a practical note experts say that if you leave a very short portion (1/4-inch) of the branch collar of the side shoots when you remove them the plant will stop producing additional sprouts within a year or two. I have observed the same thing with my own crape myrtles for many years - if I remove the suckers by pruning for the first couple of years most of the work will then be behind me.



DEAR NEIL: My dinner-plate-sized dahlias bloomed well but are now leggy. If I cut them back will they bloom again this fall?

It is little short of a miracle that they bloomed in the first place. Large dahlias are very poorly suited to Texas conditions. They need to be grown where summer temperatures are 15 to 25 degrees cooler. My guess would be that your plants will be weakened so much that they won't regrow. However, they do need to be trimmed following flowering.



DEAR NEIL: When do we trim oleanders? Mine have gotten really leggy.

Immediately after their main late-spring bloom. It's not too late, but you'll want to do so immediately. Do as little pruning as you can to lessen chance of soft new growth and subsequent freeze damage.

Neil Sperry
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