Dear Neil: I have three areas of crossvines that I planted one and three years ago. All were doing well, but I have started losing large numbers of leaves marked with purple spots. Nurseries have suggested several fungicides, but nothing has helped. What can I do? The plants are alive and blooming, but I’m still losing leaves.
A: I’ve seen those spots, but I find no reference to them on any university plant pathology websites, and that leads me to believe that it’s not disease-related. Start by watching the new 2019 leaves that the plants are producing. The moment you see any of the new leaves developing the spots, you will know that it is some type of pathogen. It might just be old leaves that are falling. I’ve been having tons of questions relative to Nellie R. Stevens hollies, magnolias and other broadleafed evergreen plants dropping leaves. This happens every year as they change their leaves out for the new season. But if the problem spreads to the new growth, you should send a sample to the Texas Plant Clinic at Texas A&M immediately. There is a $35 fee for them to culture the sample and identify the organism, if any. They will guide you as to what you should do. All the instructions are at their website https://plantclinic.tamu.edu.
Dear Neil: We have property in East Texas with a large number of trees (oaks, pecans, cedars and pines). Four tall pines were damaged by an ice storm we had five years ago. They have never recovered. Is there anything I can do to encourage new growth in these large, old trees?
A: It’s hard to answer without seeing the trees. Pines don’t have the same types of dormant buds that the others types of trees have, so they’re not as likely to send out new branches that might turn into new trunks. Helping you without seeing the trees is somewhat akin to asking a doctor how to set a broken bone without his or her having the benefit of an X-ray. I would suggest you have a certified arborist look at all of your trees, especially these four, on site. Nitrogen and water, of course, are what trees and shrubs need to promote new growth, but pines operate on their own roadmaps. The arborist will know if any corrective pruning will also be needed.
Dear Neil: Our fertilizer spreader left stripes on our lawn. Would it be OK to even it up by adding more fertilizer running the opposite direction, or should we wait a month or so?
A: It would probably be fine to fertilize it again. In fact, that’s generally what I suggest — that you apply half going east/west and the other half going north/south. If you have what is called a “drop” spreader that operates solely by gravity, this might be a good time to treat yourself to a much more forgiving rotary spreader that slings the granules out in a more random pattern. You automatically get overlap, thereby cutting the chance of the stripes.
Dear Neil: When should we fertilize St. Augustine, and what ratio is best? And when should we apply the two types of pre-emergents?
A: Feed with a high-nitrogen (for sandy soils) or all-nitrogen (for clay soils) fertilizer applied mid-April, mid-June and early September. Upward of half of that nitrogen should be in a slow-release form, that is, either encapsulated or coated. St. Augustine will normally crowd out most weeds, but if you still have annual grassy weeds you should apply Dimension, Halts or Balan two weeks prior to the average date of the last killing freeze in your community in your area in spring. Repeat 90 days later. And use one of those same materials between Aug. 25 and Sept. 5 for the winter weeds. That last time period would be when you would apply Gallery to prevent winter broadleafed weeds. You would apply the Gallery granules in a second pass over the lawn. Do not attempt to combine the two types of herbicides.
Dear Neil: What would cause these purple spots and dying leaves on our Indian hawthorns? Neighbors are having the same problems. What can we do?
A: This is the fatal Entomosporium fungal leaf spot that has riddled redtip photinias for the past 30 years. It has now moved over to the closely related Indian hawthorns. I wish that I could offer you a good control, but there simply isn’t one. It’s time to be thinking about a good replacement such as Carissa hollies.
Dear Neil: Black spot killed two of my rose bushes last fall. I tried to keep it under control, but it finally won. Now a new shoot has sprung up vigorously. I’m wondering if this is the problem you wrote about last fall? Should I dig it up and replant with a new rose?
A: I don’t know what type of rose you had there before, but this is either a sprout from the rootstock if the other rose was a budded variety or a sprout from the actual root system of the prior rose if it had been started from a cutting. Let it go ahead and bloom and see what you get. This plant is not afflicted with the fatal rose rosette virus. Visual symptoms of RRV are completely different.
Dear Neil: How can I deal with fire ants in pots with tomatoes, herbs and flowers?
A: Use a fire ant remedy that is cleared for use around edible crops. You can also use the area-wide bait treatments around the perimeter of the garden. Let the worker ants come out of the garden soil to pick it up and carry it back into their colonies to feed to the queen.
If you’d like Neil Sperry’s help with a plant question, drop him a note in care of The Eagle, P.O. Box 3000, Bryan, Texas 77805.Or email him at firstname.lastname@example.org.