This is the Q&A for the Yard and Garden show for July 27, 2018. Yard and Garden Live is a call-in radio show I do on KUTT 99.5 FM from 10-11:30 am and it will run through August 3, 2018. It can also be found on kutt995.com for online listening. If you missed a show or just want to read through the questions, I have written them all in my blog and will continue to do so throughout the season.
Guest Host: Steve Karloff, District Forester for the Nebraska Forest Service
1. The first caller of the day has tomatoes that are rotten on the bottom. What is wrong with them and what can be done?
A. This is blossom end rot, it is where the blossom end (or the end of the tomato farthest from the plant) rots. It is due to a calcium deficiency due to uneven watering. The calcium is in the soil, but uneven watering makes it unavailable to the plant. Mulch will help keep the soil at a uniform moisture level to help protect plants from this disorder. Blossom end rot is a short-term problem in our vegetable crops. It tends to only affect the plant for a the first couple of harvests of the year and then the plant grows out of it. You can cut the black end off of the fruit and eat the rest.
2. When is the best time to prune lilacs? This caller has one that is a large, overgrown lilac that needs to be pruned.
A. The best time to prune a lilac is in the spring within a couple of weeks after blooming has concluded for the season. If it is a very large, old plant, it can be pruned all the way back to 6-8 inches above ground in a rejuvenation pruning. Rejuvenation pruning does just what the name says, rejuvenates an old, less productive plant to provide better foliage, flowering, and overall health. Rejuvenation pruning can be done in the fall. The lilac will not flower for a couple of years following this type of pruning, but it will bloom again.
3. This caller planted a large amount of black walnuts last year. Now the weeds are taking over the trees. How can the weeds be controlled without injuring the trees?
A. Simazine is a pre-emergent herbicide that can be used around walnut trees that have been established for at least 12 months. This is a pre-emergent herbicide so it won’t clean up the weeds that are growing now. For those weeds, it would be best to do hand weeding with a hoe to not injure the roots of the trees and then apply the Simazine this fall. Be sure to follow the label on how to apply and how to mix the chemical.
4. A caller has a redbud tree that is 15 feet tall and is now developing a split where multiple leaders have forked up from the main trunk. What can be done to prevent further splitting? Can one side of the tree be removed to fix the split?
A. The best option would be to remove one side of the tree or bolt it together. However, removal of one side of the split would result in removing too much of the canopy of the tree. Either side of the split would be pruning off a branch that is more than 1/2 the size of the trunk, which is not recommended. Because this is a redbud, and it shouldn’t get much larger than it is now, bolting the 2 sides together may be an effective management option for this tree. A bolt in a larger tree in this situation would likely not be very effective once the tree grew to full size, but with a smaller tree it would be more beneficial. The best thing for all trees is to remember to prune them while they are young to prevent these situations from occurring, but that is not always an option and it is hard to remember to do this.
5. This caller has some pin oaks that were planted 2 years ago and are 2-4 feet tall. The new leaves are being eaten off the tree. The leaf veins are still on the tree, but most of the rest of the leaf is gone. He has looked and can’t seem to find any caterpillars. What would cause this and how can it be managed?
A. This is likely due to scarlet oak sawfly. It is a common pest of oak trees that has 2 generations per season here and we are just finishing up the second generation in the immature stage. Because the damage is mostly finished for the year and because the tree faced minimal damage, there is no need to spray for this sawfly.
6. A caller had a daylily plant that she transplanted a month ago and it died. What caused that? What time of year is best to transplant peonies?
A. June and July are not the time of year to transplant anything, it is too hot, humid and dry to move a plant. I would assume the daylily died due to heat stress. When a plant is moved, it takes time to build the roots back up to where they can survive such heat and low water that we see in the summer months. It is best to wait to tranplant anything until the spring or fall of the year so they can become established in cooler temperatures than in the heat. Peonies can be transplanted this fall, in September. Remember to keep the plant at the same depth in the soil or it will not bloom.
7. The last caller of the day sent some photos of his red maple trees wanting to know if they will survive?
A. The trees were planted last year and now one of them has no leaves on the top 1/2 of the canopy of the tree. The other has very wilted leaves. When the top half of a tree dies like this, it is likely due to a watering or root issue. I would say this tree should be replaced, it will not grow out of it. The roots could have been injured in the nursery or at the garden center he purchased the trees at. The roots also could have been injured when they were planted. The tree that is still fully leafed out may have a chance to live, give it TLC and it might pull through. Water the tree with 1 inch of water per week and add a mulch ring around the tree that is 2-3 inches deep. The leaves could be wilted due to heat and drought stress and the watering and mulch will help it to survive.