This is the Q&A for the Yard and Garden show for June 19, 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: John Porter, Extension Educator, Douglas & Sarpy Counties
1. The first question of the show was from a walk-in listener. He had a dwarf Aberta spruce tree that was shooting out long stems of larger growth that didn’t look like the original plant. What is wrong with it?
A. This is reversion. Dwarf Alberta spruce commonly reverts back to the blue spruce parents. The dwarf Alberta spruce actually came from cuttings and grafted trees from a mutation in the original spruce tree. It is unusual growth in the main plant that the plant breeders have taken to make a new tree that is new and interesting. However, even after years of maintaining those traits, another genetic mutation can occur sending it back to the original parent growth of larger and faster growing. Those reverting parts, or large, wild growing branches should be pruned back or eventually the tree will look mostly like the general blue spruce or white spruce.
2. A caller has red raspberries that have been established for 7-8 years. Now the patch has a lot of grass growing in among the raspberries. How can the grass be controlled?
A. Mulch will be the best option for this area. Red raspberries grow upright so they don’t shade out the weeds as much as black raspberries. Glyphosate or Roundup can be used carefully around the plants as well. Use some type of a barrier between the grass and raspberries if sprayed or use a sponging type of applicator or paint it on the grass.
She also wondered what to do with the old canes of the raspberry plants. Should they be cut out?
A. Yes, remove them. Raspberries have perennial roots but the canes are biennial. The first year of growth for a cane is to grow the leaves, the second year is when that cane produces berries, then after that the cane dies out. Canes should be removed during the dormant season after they have fruited.
She also has peony plants and would like to know when is best to prune those back?
A. Peonies should be left to grow throughout the year and cut back in the fall after they turn brown. They need the leaves to grow throughout the summer months to build sugars for the roots so they can bloom well next year. The flower stalks can be removed, but the leaves should be left to grow until fall.
3. A caller has blackberries growing in a garden space in the middle of his native grass prairie area. There are now canes coming up and spreading throughout the prairie. How can those be controlled?
A. Blackberries will send out runners from the main plant. These runners are still connected by underground roots, rhizomes, so spraying a chemical on them could kill the main plant as well. It is best to just dig out the plants in the grass. You could use glyphosate or Roundup on the runners, but you would need to cut the runner first to cut the tie to the main plant.
4. This caller has spruce trees that have the tips of the branches dying and those tips are hooked over like a shepherd’s crook. They also have one that the top has died. What is wrong with these trees?
A. The tips of the branches look like the damage from a disease called sirococcus. To control Sirococcus shoot blight, apply a fungicide such as chlorothalonil (Daconil, Bravo) when new shoots are ½ to two inches long, typically in May; and repeat every 3 to 4 weeks if frequent rains occur. For more information, visit this Nebraska Forest Service publication on Diseases of Evergreen Trees. You would be a little late to spray now for this year, but could treat it next spring.
As for the top dieback, that is likely canker, a common disease in spruces. You will have to cut 6-8 inches below the dead area to get rid of that. This will remove the apical dominance in your tree and cause it to grow wider rather than upright. You can train a new leader by keeping one shoot growing more upright and taller than the others.
5. Is there a certain pH that is recommended for vegetable gardens?
A. The general recommendation is to have a pH close to neutral which is 7.0 The best growth from a vegetable garden is when the pH is 5.8-6.5 Below 5.5 or above 7.5 generally requires soil modification. To get the pH you can get a soil sample kit from your local Extension Office and send it in with a sample from your garden. For more information on how to do a soil sample, visit this NebGuide For more information on fertility requirements for your garden, visit this NebGuide
She also wondered about cedar apple rust and what to use to treat the cedar trees from this?
A. It is not necessary to treat cedar trees for cedar-apple rust because the galls on the trees do not harm the tree. If you have susceptible apple trees nearby, those should be sprayed when the orange galls are seen on the trees.
6. When is the best time to transplant roses?
A. Late fall is the best time to move roses, after they have gone dormant. They can be difficult to move, so be sure to take as much of the rootball as you can get.
How can you kill scrub trees growing around the roses?
A. Cut the trees off and paint the stump with glyphosate, or Roundup. You could also use the ‘Glove of Death’ method. 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 trees to kill them.
7. How can you manage grass in the vegetable garden?
A. Mulch would be the best option. No pesticides are labeled for use in the home garden without a Restricted Use pesticide license.
8. This caller has pampas grass that has grown large and now has a dead center. What can he do to get rid of the dead center?
A. The best option would be to dig up he pampas grass and divide it and then replant the new sections. This will eliminate the dead center. The fall would be the best time to do this.
9. A caller has a maple tree that was planted 3 years ago. Last year and again this year it has leafed out but the top third of the tree will lose all the leaves early in the summer and never regrow those leaves. What is wrong with it?
A. Unfortunately, it is likely that this tree is dying and will not recover. This is most likely caused by a root issue. A large root may have been injured when it was transplanted to this location or it could have a root rot issue. After discussions, she was watering the tree all night once a week. This is too much water for the tree. A newly planted tree would have a small rootball and would only need to be watered for about 20-30 minutes once a week, even a full grown tree would only need to be watered for about an hour at the slow trickle method. This tree was likely sitting in water for a few days after this long watering which would have caused the roots to rot and this will cause dieback from the top of the tree first followed by full tree death. It would be best to remove this tree and start over.
10. This caller has a pin oak tree with branches that hang over the sidewalk. When can she prune it and where should she prune the branches?
A. Oaks are prevalent to a disease caused oak wilt that is caused by a beetle spreading the disease when it feeds on a tree. The beetles are attracted to wounded trees, pruning the tree causes a wound. Because of this, oaks should not be pruned in the summer months. They are best pruned in the later fall. Prune back to the trunk, just outside of the branch collar. If you don’t want to cut all the way back, you can cut back to a side branch that is at least 1/2 the size of the branch that is being removed. Do not just cut to a random location in the middle of the branch.
11. A caller has thistles in her pasture. She went out to cut them the other day and noticed something had been feeding on the thistles. What was that?
A. There are some insects used to manage thistles, the thistle tortoise beetle is one. It is likely that this was feeding on the thistles which will help to control the population of the thistles.
12. This caller has 12 tomatoes, 2 of them have curling leaves at the top of the plant. What is causing this?
A. Unfortunately, we aren’t completely sure what is causing this damage, but it is widespread throughout the whole state this year. It could be from herbicide damage due to chemicals still being used later in the year with the cooler spring and sudden change of temperatures to very hot. There is also thought that it could be from the beet curly top virus. This could also be from watering issues such as over watering or underwatering. It would be best to just pull the plants out because if it is the virus it can spread to the other plants and if it is herbicide injury the produce would not be safe to consume. If the other plants look ok, this would be the best option. This condition is one that is being constantly discussed in Nebraska Extension this year.
13. The final caller of the show has an American Elm tree that 1/2 of it has leafed out and the other half has died. What is wrong with it?
A. It is likely that this plant has Dutch Elm Disease, just like the elm we discussed on the show last week. There is no control or prevention for this disease. American elms were mostly wiped out in the 1960’s due to this disease but a few have survived or came up naturally. The American elms that are still alive will eventually die due to the disease, it will get to them. He can send a sample into the UNL Plant Pest Diagnostic lab for confirmation, but if it is Dutch Elm disease, the tree should be removed.
*Reference to commercial products or trade names does not imply endorsement by Nebraska Extension or bias against those not mentioned.