GARDENER'S MAILBAG: What about the dead leaves on my alive plant?
Dear Neil: All of the leaves on my loquat turned brown after the winter. They have continued to hang on the tree. New growth has emerged, but the old leaves are still there. Will they eventually fall off? They are not attractive.
We haven’t been down this road before. My guess is that they will remain on the plant for a good bit longer. If it were my loquat, I would try to clean it up sometime this fall. I would trim any dead branches out, and I would remove any errant growth that causes the plant to be misshapen. Then I would remove as many of the brown leaves as I could reach. Hope that helps!
Dear Neil: You have often recommended Nellie R. Stevens hollies as landscape shrubs. I’ve been very pleased with the ones I have planted, but they have begun to develop small holes in their leaves. What are these, and what can I do to control them?
I have seen those holes in the leaves of my own plants for years. They were never serious enough for me to spend much time researching them, but your question has pushed me over the edge. After half an hour of online research I find that this is damage of the cranberry rootworm beetle. They feed at night, which explains why we don’t usually notice the insects themselves, but their feeding can be fairly unattractive if it’s on plants near high-visibility places. Clemson University has a very thorough writeup on the insect (https://hgic.clemson.edu/factsheet/cranberry-rootworm-beetle/). They recommend foliar sprays of a variety of different organic or inorganic insecticides in spring and summer or soil drenches of the systemic insecticide Imidacloprid applied after the hollies bloom in late spring.
Dear Neil: All of these vincas were bought at the same time, planted in the same potting soil and cared for in the same way. One of them now is wilting and showing steady decline. What can I do to turn it around? What is wrong with it?
The close-up photo of the afflicted plant shows that it has the water mold fungus called Phytophthora. That is a very serious threat to vincas. It attacks their stems and causes parts of the plant to wither and the rest plant to follow suit very quickly. The group of vincas known as Cora XDRs were bred to offer resistance to the fungus, but it can still be a problem if there is poor drainage, or if the stems are hit with splashing water filled with spores. This disease took vincas from one of the South’s most popular summer annuals to an also-ran for 15 years, and it wasn’t until the Cora series that we had any sense of hope. There are things you can do for next year. Buy Cora XDRs if you didn’t this time around. Do not grow vincas in the same soil two years in a row. Wait until it’s quite warm and dry (mid-June) to plant your vincas, and then set them into loose, well-draining potting soil. Avoid hard, splashing watering and position the pots (assuming you’ll be growing them in containers as you did this time) where they’ll have good air circulation.
Dear Neil: I have fungal leaf spot in a Monterey oak that is dropping its leaves. Is there any remedy?
You did not enclose a photo with your question, so I really can’t get very specific with my answer. Leaf drop has been extremely common on all oaks that were damaged by the cold last February. Monterey oaks would be near the top of that list because they are one of the least winter-hardy of all of our oaks. Without a photo, the first thing I would do is rule out latent freeze damage as the cause of the leaf drop. I would advise you to have a certified arborist look at your tree.
Dear Neil: Please tell your readers not to give up on their sago palms. I almost cut mine down when we had brush pick-up day, but here they are again. This is at a place we have in South Texas.
This has been the most unusual growing season of my career (and there have been a lot of seasons in that career). A lot of plants have suffered severe freeze injury and are now coming back. With some of the plants we have to decide whether we are willing to wait. With sago palms it’s certainly justified. Thanks for your note!
Dear Neil: My hybrid purslanes’ blooms aren’t as large or as prolific as they were in the spring. How can I get that all back?
They consume a lot of nutrients over the course of a summer. This summer there has been enough rain in many parts of Texas that those nutrients have been leached out of the soil more than usual. Apply a water-soluble, high-nitrogen fertilizer every time that you water them for a couple of weeks.
Dear Neil: We have both native and hybrid oak trees in our yard. Given the extreme cold of last winter and the damage that it caused, is it safe yet to prune them?
Yes. In fact, it would be safe even in a normal year. To explain what you’re asking to others, plant pathologists and foresters have taught us that we should not prune oak trees during the active growth period of spring and early summer. The fatal fungus known as “oak wilt” is active during that period. By mid-July the fungus becomes inactive, so from that time through the rest of the summer, all fall and up until mid-February we can prune oaks – just not in the springtime. It’s also imperative that we follow good pruning practices. With oaks that means we must always seal every cut larger than a broomstick in diameter with black pruning paint immediately after we make each cut.
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