GARDENER'S MAILBAG: How can I stop my hybrid poplar from yellowing?

By Neil Sperry
Special to the Herald Democrat
Hybrid Poplar

Dear Neil: What can I do to stop the leaves on my hybrid poplar from turning yellow and falling off?

I don’t see anything out of the ordinary in your photo. The older trees in the background also have yellowing leaves. It’s just that time of year. Cottonwoods and poplars have all been dropping leaves for weeks already. It’s the nature of fast-growing, large-leafed shade trees. Keep your tree moist all through the winter and spring and you should see a burst of new growth in the spring.

Dear Neil: My plumeria that I thought I had lost in the February cold when our garage dropped below freezing for a couple of hours eventually came back. It has grown really well, and now I need to repot it. I’m thinking about putting it into a half whiskey barrel. Would that be a good idea? Could I move that into and out of the garage this winter?

Plumeria

I would opt for a comparably sized terra cotta pot – something with heft that would provide ballast to help keep the plumeria from tipping over. Wooden half-barrels don’t work well. The metal banding rusts and eventually pops. They don’t handle the pressure at all well, and your plant will be brittle enough that having the pot fall apart would put it at great risk.

Dear Neil: Why does a wisteria that was bought in bloom never bloom now, years later? What can I do to help bring it back into flower in the spring?

Spring Bloom Of Crossvine Variety Tangerine Beauty

There are several factors that contribute. In fact, it often is a combination of more than one of them leading to a plant’s failure to set buds. This is my most common question pertaining to vines. See if any of these fits your situation. Wisterias must have full sun to bloom to their best potential. The heavier the shade is, the poorer the flowering performance is likely to be. They must not be pruned extensively in fall or winter. That’s when the plants are busy setting flower buds for their early spring blooms, and any pruning at those times will just remove the primordial flower buds. Also, if you apply nitrogen fertilizer to turfgrass near your wisteria it will often impede its ability to set buds. So will consistent watering in fall. Both will cause the plant to remain vegetative instead of setting buds. The answer is in there somewhere, but it’s hard for me to pull any one out and say that it is your concern without watching you operate over an extended period of time. Hopefully I’ve gotten you closer to a solution, however.

Dear Neil: I’m fed up with St. Augustine and all of its problems, plus all the water it consumes. I’d like to switch over to a native grass. What can you tell me about buffalograss?

Buffalograss Turf From 9 Years Ago Is Now All Bermuda

My dad was a range ecologist with Texas A&M for more than 25 years. As a kid I noticed a native grass growing in roadside ditches and that no other grasses or weeds were invading it. He told me it was buffalograss, and I shared the same interest you have. Then, in the early 1990s, several hybrid buffalograss varieties came into the market with a great deal of fanfare. They were planted in some very prestigious places (and one not-so-special location – at our house). What we all found out in horror was that it was impossible to keep native bermudagrass out of the buffalograss. If there was any bermuda anywhere nearby, within a couple of years the buffalograss was completely crowded out. By 1995 I had quit recommending it for all but the most special of settings. I’d suggest you go directly to native bermuda, otherwise sold as “common” bermuda. It has the features you’re seeking, even though it’s only a “naturalized” citizen of Texas.

Dear Neil: I have a persimmon tree growing in a very large pot. Last year it had four persimmons, but the raccoons got them just before they ripened. They also damaged the tree. This year I used a net to protect the tree. Things were going well and six persimmons were developing. However, about five weeks ago the leaves curled and fell and the fruit dropped, too. Now new leaves are emerging. Did I water too much? Too little? Is it leftover damage from the cold?

I’m just guessing from those few facts, but I’d say it got too dry one time. If the soil had been too wet the roots would have been rotted and it would not have put out new growth. If it had been the cold it never would have leafed out and grown that well in the first place.

Dear Neil: Why do you never talk about crossvine? It’s evergreen, non-invasive with multi-seasonal orange blooms that hummingbirds love.

Because no one has asked about it. Now you did, so we can talk about it. It’s a great vine that grows both by twining and by clinging. I’ve grown it for years, but I’ve not shared the “multi-seasonal” blooming experience you apparently have. At least 98 percent of my plants’ flowers have always been in the spring. It’s semi-evergreen in the northern half of the state. And my plants and those that I’ve observed seem to have a productive life expectancy in landscapes of 8 or 10 years. After that, the ones I’ve observed seem to thin and become rangy.

Dear Neil: We have some arborvitae plants that we’ve had for years. Recently they have started to develop branches with orange needles that have eventually died. What would cause that? Where can we go for help?

It could be spider mite damage. They certainly will attack arborvitae and junipers. Thump a declining (not dead) branch onto a sheet of white paper. If you see nearly microscopic specks starting to move about freely almost immediately, those would be the mites. Use a product labeled for their control. Otherwise, you may want to send a declining (not dead and crisp) sample to the Texas Plant Disease Clinic at Texas A&M to see if there are any active pathogens involved. Their website has all their information and mailing instructions. Without a photo I can’t get much closer.

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