This is the Q&A for the Yard and Garden show for June 21, 2019. 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 2, 2019. 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 question of the show was about a Colorado Blue spruce tree that is turning brown throughout the whole tree. It seems to be starting at the ends of the branches. What is wrong with it?
A. This could be that it is simply too wet. The excess moisture this year is causing problems with a lot of our plants. Colorado Blue spruce trees grow best in the conditions in Colorado with a lot less humidity and moisture. Steve has seen quite a few spruces turning brown this year, most likely due to root rot issues from the high precipitation from this spring. Unfortunately, there is nothing that can be done to fix this problem.
2. Can you still prune forsythia shrubs this late into the year?
A. No, it would be better to wait. The general guidelines are to prune spring blooming shrubs within a couple of weeks after they have finished blooming for the year and to prune summer blooming shrubs in the late winter before they bud out for the year. At this point, pruning the forsythia will affect the blooms and it would be too hot to prune in the summer.
3. A caller has cherry trees that he planted in the spring. Now the leaves have wilted and died back. Why did this happen?
A. After discussion it was determined that the trees were purchased from a mail-order service and were delivered bare root. He planted them within a day of receiving them, which is advised because they will dry out quickly with no root ball to hold water. It was advised that he scratch the bark on some small twigs to see if it is green underneath the bark which means the tree is still alive. If under the bark is brown, the tree is dead. It could be an issue from the nursery or through the shipping process. It would be better to purchase trees locally.
He also wanted to know if he could remove the cedar trees on his property to eliminate the problems from cedar-apple rust?
A. No, the spores from cedar-apple rust will spread up to 2 miles. Removing the close cedar trees won’t stop the disease because it would be nearly impossible to find a location in Nebraska where you can get more than 2 miles away from a cedar tree. It is best to just spray susceptible apple trees or plant new trees that are resistant to the disease.
4. This caller has a weed called pineapple weed. Can you use a granular herbicide to control it?
A. Pineapple weed is an annual plant that is often found in poorly maintained areas, typically along driveways or along gravel areas. This weed can easily be controlled earlier in the season with a pre-emergent herbicide such as dimension or another that contains dithiopyr. For post-emergent control, glyphosate products such as Roundup could be used. The granular herbicide will likely not be very effective on pineapple weed.
5. A caller has strawberry plants that are producing very small berries and not a lot of those. It was hit by herbicide drift at one point, but seems to be recovering. Is the herbicide causing problems with fruit production or why are there so few berries that are so small?
A. The herbicide drift may impact the fruit development if it was hit while it was flowering that could have damaged the flowers before they were able to produce fruit. Otherwise, the small fruits are fairly common for the everbearing types of strawberries. Since they continue to produce through the season they will not produce the larger fruits that June bearing plants would have.
6. A walk-in listener has a hollyhock plant with a lot of brown spots that are raised bumps on the underside of the leaf. What is causing that?
A. This is hollyhock rust. This is a common problem for hollyhocks, especially in this wet year. Remove the heavily infested leaves if you cannot remove all infested leaves and destroy those. You can use a copper fungicide on the plants to reduce the spread or re-infestation. At the end of the season, be sure to clean up all the leaves and plant material to reduce overwintering location to see less of the rust next year.
She also wanted to know what would cause a row of holes in her canna leaves?
A. This would be from Canna leaf rollers, a caterpillar. They can be controlled with a systemic insecticide applied to the cannas early in the season before the damage begins or by using Bt or Sevin once the damage begins.
7. This caller has an ash tree she would like to save from Emerald Ash Borer. What can be done now to ensure it lives?
A. Wait until Emerald Ash Borer is found within 15 miles of the tree prior to beginning treatments. Treatments are not necessary for an insect we haven’t found in the area. Even if defoliation has began on the tree when it is first identified in the area, treatments can be successful. Each time trunk injections are done they wound the tree leading to more problems.
8. How do you eliminate woodchucks from a garden?
A. They can be deterred with the use of a heavy-duty fence around the garden. The fence needs to be 3 feet tall and made of 2 inch mesh woven wire or heavy poultry wire. They can also be trapped using apples or carrots as bait. For more information on Woodchucks, view this guide.
9. Can you grow an avocado tree in Nebraska?
A. This would have to be an indoor tree. They will not withstand Nebraska winters outdoors.
10. A caller has wild roses that have some dead stems throughout the plant. Should those dead stems be removed?
A. Yes, you can cut out the dead canes of the shrub at any time.
He also wondered about tiger lilies. They were constantly mowed last year and haven’t come back this year yet. Will they come back?
A. If they haven’t regrown yet, it is likely that they have died. I would suggest replanting.
11. This caller has a big, green leafy plant that grows 4 feet tall and 6 feet wide with leaves similar to rhubarb plants. What would that be?
A. This sounds like Common Dock. It can be mowed off or sprayed with a roundup or glyphosate product now. In the fall, you can treat the plant with a 2,4-D product.
12. The last caller of the day has roses with holes in the leaves. What is causing that?
A. This is likely due to rose slugs. They are a common issue right now in roses. They will likely be finishing up their damage cycle soon and then they will pupate and become adult sawflies. The damage is minimal and they don’t need to be controlled with an insecticide which could harm pollinators coming to the rose flowers.