In the garden
Q I have now found rose rosette on at least three of my roses — all Knockouts, in two separate areas. I have dug them up and disposed of them properly.
The one I just dug is the first I have found in a particular perennial flower bed with other Knockouts, climbing “New Dawn,” “Improved Blaze” and other climbers. Do I have a chance to preserve these? What is the best immediate course of action and action in the coming fall and spring? Someone mentioned that he nipped the ends of his roses. I think he meant in the fall when they were beginning to go dormant, to protect from the disease. So, any suggestions would be greatly appreciated.
A Rose rosette is a bad disease. It is a virus, so there is no cure. It is spread by mites feeding on an infected rose and then passing it on as they feed on another rose bush. Pruning your roses in late February can help reduce mite populations, and a spray of a dormant oil after pruning can help kill any overwintering insects. I do not recommend pruning in the fall. If we have a severe winter, early pruning exposes more of the plant to damage. If a bit of the top dies back due to cold, that isn’t a problem since we will be pruning it off anyway, but always prune in late
winter/early spring. Rose rosette can present itself with various symptoms, including red stems, excessive thorniness, distorted or mottled leaves, or bunchy new growth — often referred to as witches’ broom. If you see a symptom, you can try cutting it out several inches below where the damage is visible and sterilize your pruning shears. If the plant continues to grow with no problems, you have stopped it. If you see symptoms on another branch, the disease is systemic in the plant, and the entire plant needs to be removed — roots and all. There is still debate about replanting roses back in the same site, but I think it would be advisable to take a year or two off from roses in that area before replanting. Miticides or insecticidal soap can help kill mites on neighboring plants that have not been infected. But if you have a yard full of roses, that is a tedious process.
Q
The blackberries have fruited, and the fruiting canes have been cut out ready for next year. The new canes are growing at an unprecedented rate, many at 8 feet already. Should I prune them back to encourage branching? They already are much taller than the birdcage that I will re-install next year after pollination. Guidance would be appreciated.
A
Blackberries can be prolific growers. I definitely recommend pruning the new canes to a manageable height, otherwise, you will need a ladder next year to pick them. Try to keep the canes no taller than 4 feet. This not only makes picking easier, but it also forces side branches which will bear the fruit and makes your canes more stable.
Q
My wife and I would like to know how to get rid of nutgrass. We keep spraying, but it just keeps coming back. Nothing works.
A
Nutgrass is a tenacious weed in the sedge family. I have seen it come up in an asphalt driveway! It is a perennial weed that forms a small nutlet or underground bulbous structure, which makes it hard to kill. If nutgrass is growing in your lawn, SedgeHammer is an herbicide that gives decent control. SedgeHammer is also labeled for use around shrubs, but some foliar damage has been seen on some species of ornamentals. Roundup or glyphosate can be used as a spot treatment. It is nonselective and will harm desired plants, so only spray what you are trying to kill. Unfortunately, one application of any product is not going to eradicate nutgrass or nutsedge. If you have a small area of it and you have time, you can dig the plants up with their roots to try to eliminate them.
Q
I am worried about my tulip tree. It was planted in 2011 and bloomed for the first time this past spring. The leaves are much smaller than past years and have a lot of large and small black spots and areas on them. Some are turning brown and curling up at the edges and some are turning yellow and falling already. The bark at the ground is loose and coming off. I have a sprinkler system and use a lawn chemical company to fertilize my trees and shrubs. It has been a healthy and beautiful tree until this summer. Any ideas about what may be going on?
A
I would try to remove the grass that is in direct contact with the tree. Have a slight buffer zone between grass and tree trunk. That will prevent any wounding of the trunk from a lawnmower or weed edger. Have a soil test taken. If your pH is out of kilter, it can affect the tree’s growth. The leaves in some of the pictures appear chlorotic with darker veins. Talk to your lawn care provider and find out when they are spraying and what products they are using. Some chemicals affect trees more than others. If you can know in advance of spraying, you can make sure the trees are well irrigated in advance to prevent too much uptake of chemicals. This fall, rake the leaves that fall and get them out of the yard. We have had several leaf spot diseases this year with all the early wet weather. It is too late to think of a spray program now. I also think your tree should be getting ample nutrition from the lawn service. Keep investigating and see how it leafs out next spring.
Retired after 38 years with the University of Arkansas Cooperative Extension Service, Janet Carson ranks among Arkansas’ best known horticulture experts. Her blog is at arkansasonline.com/planitjanet. Write to her at P.O. Box 2221, Little Rock, AR 72203 or email jcarson@arkansasonline.com