This is the Q&A for the Yard and Garden show for June 26, 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: Kyle Broderick, Plant Pathology Extension Educator
1. The first question of the show was from a caller who missed the answer last week on the show regarding controlling grass in her red raspberries.
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.
2. A caller has a mandevilla with leaves that are turning yellow with black edges. She also has a gardenia that is getting yellow leaves with black edges. What is this and can she fix it?
A. These plants are growing in containers being watered often enough. Be sure to check the drainage when watering to ensure the drainage holes are not clogged. Water containers until water runs out of the drainage holes. If that isn’t happening there may be a clog which could lead to root rot because the plants would be sitting in water. Be sure to test the soil before watering to ensure it is dry. Stick your finger into the soil to see if the soil is dry, if it is still wet, do not water until it has dried.
3. This caller has a new lawn, she thinks it is fescue. It was planted last year and last fall it looked great. However, when the hot, dry weather began this year, a few patches in the lawn dried up and look dead now. The lawn was described as drying up almost overnight as soon as the heat started and there was a black coloration to the plants. What is wrong with the lawn?
A. This could be drought injury, grubs, or pythium blight. The new plants likely don’t have a full root system yet which would cause it to dry up faster in the heat. Watering 1-1.5 inches per week would help with drought or heat stress. If she pulls up the turf and there are no roots, it would be from grub damage. Grubs can be treated now with a lawn grub control such as Merit or Grubex. If she takes a handful of the blades and puts them into a baggie and leaves them overnight, she might notice a fishy odor that would indicate pythium blight. Pythium will go away on its own, it doesn’t harm the crown of the plant and it will regrow.
4. A caller planted new grass a year ago after a new home was built. It was growing good, but now there are some grass plants that turn brown and have stickers on them. Would that weed have been in the turf seed? How can it be managed?
A. These are likely sandburs growing. They were not in the grass seed, they were most likely from the soil. When a new home is built, the area that was undisturbed before has now been worked up. Sandburs live in rocky, bare soil areas where grass doesn’t grow. They would have already been there when the home was built. Sandburs are an annual grassy weed, similar to crabgrass. They can be controlled with crabgrass controls. In the spring use a crabgrass preemergence herbicide and now that the sandburs have already germinated for the year, Drive or another product containing quinclorac can be used.
5. This caller has a tree row at his house. There are old firs or pines that seem to be dying out and now he has planted a row of blue spruce. The blue spruces are turning brown, starting on the inside of the plant moving outward. The damage on these spruces is on the side facing the old trees. What is wrong with these trees and what can be done to help them?
A. The old trees could be nearing the end of their life and may just be dying of old age. This does happen. As for the blue spruces, it could be a needle cast disease which is common on spruce trees and is prevalent now. It is not effective to spray with fungicides now, but next spring they can be treated with chlorothalonil. They should be sprayed when the new needles are half expanded and then again 4 weeks later when the needles are fully expanded. There could also be some problems on the spruce trees from the location near the dying firs or pines. They are likely not getting the airflow they need and the needles are staying wet longer. This could be intensifying the needle cast disease.
6. A caller wants to know what our opinion is on transplanting trees now? He would be moving them with a tree spade.
A. Regardless of the size of the tree or how it is moved, it would be difficult to keep a tree alive in this heat. If planting from a container grown tree, there would not be much for a root system on the new tree so it would have difficulty getting water as often as needed. If it is brought in with a tree spade, many of the large roots will be cut and it would still be hard for the tree to get the moisture it needs. It is best to plant trees in the spring or fall, when it is cooler and rains more often to keep the tree well watered through the establishment period. They are best planted prior to Memorial Day and then again after Labor Day. We advise against planting in the summer months.
*Reference to commercial products or trade names does not imply endorsement by Nebraska Extension or bias against those not mentioned.