QUESTION: I’m curious about my knockout rose bushes dying. I’m sending pics of a new shoot and one I cut off several days ago. I realize it’s dried up, but can you can tell anything from it and the size? That shoot came off the bottom of the bush.
ANSWER: You’re seeing symptoms of rose rosette disease. Unfortunately, it has become quite common on knockout roses. The dwarfed red leaves that grow close together and soon die are the textbook symptoms. There is no control for this disease, and lots of knockouts are dying from it. If you have more than one plant, sterilize your pruners after making cuts on this plant when deadheading or removing damaged stems. Sterilizing the pruners between cuts will reduce the chances of the disease spreading to other rose plants that you are pruning. If it is RRD, and it continues to die back, you’ll want to avoid planting another rose in that place.
QUESTION: We have a good crop of daylilies that blooming very well, but the foliage is yellow. I’m wondering if we cut them off when they stop blooming and fertilize in fall, or just what?
ANSWER: Your daylilies have likely gone off-color for two reasons. First, the heat and dry conditions. Second, many plants will bypass leaf support while producing their flowers. Once your daylilies have finished blooming, you can fertilize them. This should help the leaves and help them store food for next year’s blooms.
QUESTION: My lawn has suffered this summer. Should I put down 19-0-5 on my lawn in August followed by grass seed a month later in September?
ANSWER: The fertilizer you mentioned is a good maintenance fertilizer for turf. However, my recommendation would be to use a starter fertilizer in early September and then plant your grass seed. About 30 days later, you could use the 19-0-5 to help continue the development of your new seedlings.
QUESTION: I gave up trying to grow yummy heirloom tomatoes thanks to wilt. This year, I planted several different disease-resistant hybrids and fertilized with compost and bone meal, with no added nitrogen. I got lots of foliage, little wilt, but few tomatoes. I’ve never tested my soil; could that be part of the problem? The strange thing is, I used to get an abundant harvest before I switched to heirlooms several years ago.
ANSWER: The main issue with heirloom varieties is that they have little or no resistance to verticillium or fusarium wilt. Consequently, switching back to hybrid varieties was a good idea. However, I don’t think having previously grown heirlooms created the problem you’re seeing. Since you have never tested your soil, it could be that, even with the compost and bone meal, your phosphorus level may be too low for good fruit production. Compost has some nitrogen, but more potassium. Also, if your soil pH has gotten out of the ideal zone for vegetables, that would prevent your plants from taking advantage of the phosphorus in the soil. Ideally, the pH for tomatoes is 6.2 to 6.8. Have your soil tested soon, so you can make any needed amendments in time for them to benefit your garden next year.
QUESTION: Within two days, lots of leaves on my rose of Sharon have turned yellow and started to drop. Any idea what’s causing it? Will it kill the tree, and can I do anything to help it?
ANSWER: My thinking is that the yellow leaves are the result of the heat and recent dry conditions. This plant is prone to root stress. Also, the spots on the leaves are caused by a fungus. At this point, you can collect the leaves as they fall and destroy them. This will reduce the number of spores that will overwinter in your yard. In the spring, you can treat the new growth with a fungicide to help prevent the return of the fungus. As for the leaf drop, it is quite common on these plants, but protecting the root system from dry conditions will help.