This is the Q&A for the Yard and Garden show for May 29, 2020. 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 July 31, 2020. 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: No guest host due to COVID-19 and social distancing
1. The first caller of the show has tomato plants that now is developing “skinny” leaves. What is wrong with them?
A. The leaves are skinny and deformed. This is likely from herbicide drift, it is hard to say for sure without seeing the plants, but it sounds most like herbicide drift. This has started to become a problem again this year due to the change in weather. As we warm up, we see more problems with 2,4-D and dicamba products that turn to a gas and move to non-target plants. Tomatoes are very sensitive to drift from 2,4-D or Dicamba products. They should grow out of the damage, however because we don’t know exactly what product hit these tomatoes there is no way to know for sure when the product will be out of the tomatoes. I can’t say when or if these tomato plants will be safe for consumption this year.
2. This caller has a very large hosta. When can it be divided?
A. Early spring is the best time to divide hostas, once they have emerged from the ground but before the heat of the summer. It might be a little late to divide the plants this year due to the hot weather expected next week. If they are divided now, be sure to keep them well watered.
3. When can oaks and maples be pruned?
A. The new pruning recommendations show that pruning is best if done in late spring, so late May to early June for Nebraska. Now would be a good time for most trees, however, oaks are susceptible to oak wilt if pruned during the summer months. It is best to wait until fall, September or October, to prune oak trees to avoid this disease. Maples, can have a heavy sap flow in the spring, they can be pruned now, but may leak sap, sometimes large quantities. They would be better to prune in the fall also.
4. A caller was going to use Grass-B-Gon on some weeds she recently hand-pulled to reduce the hand-pulling in the future. How long should the regrowth be before she applies the grass killing product to her landscape beds?
A. As long as you start to see some new, green regrowth, the product should work. According to the label, it should be applied anytime weeds are actively growing, which would be when you see them green up again around your landscape plants.
5. This caller is on her second round of planting tomatoes and they are turning yellow again. She planted the first in late April and then again recently. In the new planting one plant is starting to turn yellow. She is using straw mulch on most of the plants but is using grass mulch on the one plant that is turning yellow. What is wrong with her plants?
A. The first round of plants were planted too soon and we saw quite a bit of cold weather later in the season this year than many other years. She did cover the plants on the sides, but left the top exposed. Frost would have settled down onto the plants and killed them. The new plants are doing fine except the one plant that has grass clippings on it. The lawn has been treated with broadleaf weed control as well as crabgrass control this year. The labels will tell you not to use the clippings on the garden for the season or for a period of time. If that isn’t being followed and this is the one plant that is looking bad, I would assume that the grass clippings are the problem. Be sure to use clean grass clippings or use straw for all of the plants.
6. A caller pulled 3 mature barberry bushes with a pickup truck and then decided to replant them after all. What should be done to keep them alive? Should they be fertilized?
A. Pulling these plants out with a pickup truck and chains would have drastically damaged the cambium layer which can reduce the flow of water and other nutrients through the plant. They were also kept out of the ground for a week before being replanted. These plants could pull through if they are tough, but you will need to make sure they are kept moderately watered. Don’t overwater, but don’t allow the plants to dry out either. A slow trickle for about 10 minutes a couple of times per week will help to rebuild the roots. Do not fertilize them. Fertilizing a stressed plant can further stress the plant. Only time will tell if they can survive.
7. This caller has lilacs that are looking bad and didn’t bloom well. What can be done to help them? When can they be pruned?
A. Sounds like this lilac is in need of a rejuvenation pruning. This is where you cut the plant off about 6-8 inches above the ground level to rejuvenate the growth. It will reduce insect problems and push new, young growth to provide better blooming and have a healthier plant. This can be done in the fall for best results.
8. A caller had bagworms on her cedars last year. She also noticed a lot of praying mantis egg cases, she knows they are a good predator. Are the praying mantis’ helping to control the bagworms?
A. Praying mantis’ are not a major predator of bagworms. They prefer feeding on aphids and others.
She also wondered about her forsythia that was injured by the late frost this year. It didn’t bloom this year and she had to cut back some of the branches. Will it bloom next year now or did this damage the blooms for next year as well?
A. The blossoms are set on the new growth that will form this summer. As long as they are pruned back within about 3 weeks after their bloom period, they will still bloom next year. This is why we prune forsythia just after they bloom rather than in the late winter. This forsythia should still bloom next year.
She had one final question, how can she control a clover-type weed growing profusely in her iris beds?
A. This will be difficult to do without harming the iris plants. She could spray with Roundup using a piece of cardboard as a barrier between the weeds and the iris plants or she could use the “glove of death”. This is when you wear a chemical-resistant glove and then put a cloth glove over that. Then, dip a few fingers of the gloved hand into Glyphosate and rub those fingers along the stem and leaves of the bindweed to kill it.
9. What can be done to control elm saplings in a windbreak?
A. You can go through and cut off the trees and follow that up with a stump treatment using either 2,4-D or a glyphosate product, such as Roundup. The Roundup would be better this late into the year to avoid volatilization issues from the 2,4-D in the heat. Use the concentrate and just paint it on to the freshly cut stump for best control. Do NOT use Tordon, that will likely kill the spruce trees, and it is against label directions.
10. A caller planted grass in the spring. It is getting to about 2 inches tall now. When can he spray the weeds coming in with the grass?
A. You should wait until after 3 times mowing the new lawn before any herbicides should be applied to the grass to avoid injury. However, by that time, it will be too hot to use any 2,4-D products, which will turn into a gas and move to non-target plants and injure them in temperatures above 80-85 degrees. It would be better to just wait it out and spray in the fall to manage the weeds after the turf is more established. The fall is a better time to treat for perennial broadleaf weeds because it is when the plant is taking nutrients back into the root system and it will take more of the herbicide with it. Spray twice in the fall, once in mid-September and again in early to mid-October.
11. This caller has a hydrangea that didn’t look like it was going to live through the late frosts this spring. She did notice that it is finally coming up but it is only about 3 inches tall and is setting blossoms on. Should she remove those or let the plant bloom at such a small size?
A. It would be best to remove those blooms to allow the plant to grow a bit more before trying to bloom. All the energy in that plant would push into flower production, at such a small size, it would be best to allow the plant to build leaves and the root system to help it so it comes back next year.
12. A caller wants to know what to do to keep iris blooms from falling over?
A. Sometimes if the flower is too heavy it can fall over a bit. There are metal rings you can purchase to put in flower beds around plants that fall over to keep them upright, but nothing else will work for this. The flower is just too heavy for the stalk.
13. If branches on a tree or shrub are already dead can they be pruned off now?
A. Yes, dead branches should be removed as soon as they are noticed to prevent injury or damage from a falling branch.
14. The final call of the show asked if they should be fertilizing lilacs that were planted 3 years ago?
A. Fertlilizer doesn’t need to be used on plants that are growing just fine. Most trees and shrubs can get the nutrients they need to survive from our soils. The best thing is to do a soil test prior to adding any soil amendments, nutrients can build up to a too high level which can also damage the plant.
*Reference to commercial products or trade names does not imply endorsement by Nebraska Extension or bias against those not mentioned.