This column will be published each Wednesday during the growing season.
Note: Ask the Expert is written by Iowa State University Extension horticulture specialists. The questions are chosen from those submitted by users of the ISU Hortline.
Buds form on my peonies, but don’t open. Why?
There are several possible explanations why peony buds may fail to open.
Peonies bloom best in full sun. In partial to heavy shade, plants are weak and may not be able to supply adequate food to the developing buds. As a result, the undernourished buds don’t develop fully. Peonies growing in partial to heavy shade should be transplanted to a sunny site in September.
Fungal diseases, such as Botrytis blight, may infect peony buds. Infected buds turn brown or black and fail to open. Fungal diseases are most common during cool, wet, spring weather. Sanitation is the most effective means of controlling Botrytis blight and other peony diseases. Cut off the dead debris at ground level and remove it from the area in late fall or late winter.
The flower buds may have been damaged by a late frost or freeze. While the plants themselves can tolerate a freeze, the buds are more susceptible to freezing temperatures. Unfortunately, little can be done to avoid this problem.
Extremely dry conditions in early spring are another possible explanation. In dry weather, water plants deeply once a week during bud development.
When should I stop harvesting asparagus?
Discontinue harvesting of well-established asparagus by early June in southern Iowa and mid-June in northern areas of the state. If harvested over a longer period, the plants may be weakened, which can seriously reduce future yields. Allow the asparagus stalks to grow after the last harvest.
How can I prevent rabbit damage to the vegetable garden?
The most effective way to prevent damage to the vegetable garden is to enclose it with a chicken wire fence. A 2-foot-tall roll of chicken wire should be adequate. The fence should be supported by strong wooden stakes or metal posts. The bottom 2 or 3 inches of the fence should be buried in the ground to prevent rabbits from crawling underneath it.
When can I remove the foliage on my tulips and daffodils?
The foliage of spring-flowering bulbs should not be removed until it has turned yellow and begun to die back. The length of time it takes the foliage to die back depends on bulb type, weather and cultural practices. Most tulips and daffodils don’t die back until late June or early July. Premature removal of plant foliage reduces plant vigor and bulb size, resulting in fewer flowers the following spring. After the foliage has yellowed, it can be safely cut off at ground level and discarded.
Is there anything that can be done to stop toadstools from coming up in the yard?
Mushrooms (toadstools) are the reproductive, or fruiting structures, of fungi. Their appearance usually indicates the presence of decaying tree stumps or roots in the soil.
While mushrooms in the lawn are somewhat annoying, most cause no harm to the turfgrass. There is nothing that can be applied to the ground that will prevent them from emerging. Simply mow them off or rake and discard them when they appear. Eventually, the mushrooms will stop emerging with the arrival of warmer, drier conditions. Unfortunately, this is probably only a temporary reprieve. It’s likely the toadstools will periodically appear over several years during favorable environmental conditions. Their periodic appearances will end when the stump or roots in the soil have been completely broken down by the fungi.
Got gardening questions? Contact the Hortline at (515) 294-3108 (M-F; 10-12 & 1-4:30) or e-mail us at firstname.lastname@example.org. For more gardening information visit us at Yard and Garden Online (www.yardandgarden.extension.iastate.edu)