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What killed the mountain ash fruit? Ask Mother Nature

Deformed coneflowers should be pulled if they don't come around. (Sarah Smith / Enterprise)

Q: I have 16 coneflowers, but six of the flowers have deformed buds. Could something other than aster yellow be to blame for this problem?

A: Generally, no. However, I'm sure something obscure might do the same thing. If it continues to progress, get the coneflowers yanked out. You don't want the hoppers to be spreading this to other plants.

Q: My cucumbers flower a lot and grow tiny fruits, but then the fruit falls off. I plant self- pollinating cucumbers in my small greenhouse in good loam that is fertilized with composted cow manure. In previous years, I added compost liberally. This year, I didn't add a lot. The plants look healthy and do not have yellow or downy mildew. The soil may be too wet. Do I have a nutritional deficiency?

A: The fruits that are not fertilized will fall off. I don't know what else to tell you. It could be a temperature problem. Many times high day or low night temperatures can cause the fruit to abort.

Q: Caterpillars have taken a liking to our young golden willows. They defoliated one tree and have moved on to the surrounding trees. The caterpillars remind me of thistle caterpillars. Are they related?

A: These are mourning cloak butterfly larvae. While the adult is beautiful and admired when seen fluttering around flowers, she lays eggs at a rate of 200 to 500 at a time. These gregarious little characters then hatch and begin feasting on willows. After that, they move on to other surrounding trees. Most trees can tolerate an occasional defoliation with no problem. The thistle caterpillar yields the painted lady butterfly, which is a Lepidoptera just like the mourning cloak butterfly, but that's as far as they go in being related.

Q: I have some red raspberry plants in my yard and want to add some golden raspberry plants. Can I plant them in raised beds about 5 feet apart or do they need to be at a greater distance apart to prevent cross-pollination?

A: You can plant them without worrying about cross-pollination. All raspberry cultivars are self-fruiting. Besides, the pollinating bees would find them if they were 50 feet apart. Enjoy!

Q: What would stop a mountain ash from producing fruit? A homeowner brought in leaves with sun scorch and said the mountain ash wasn't producing fruit. Other than the scorch, nothing is wrong with the tree. I asked twice about fire blight and he said it is not present on his tree.

A: The flower buds are more sensitive to low temperature extremes than the foliage buds. My best guess is that your weather killed the buds when they were coming out of dormancy. If they did flower and no fruit resulted, then it again is a weather-related problem. It could have been rainy, windy weather at the time the sexual parts of the plant were ready for fertilization or low temperatures that kept the pollinators from being active. Another possibility is a frost that killed the pistillate part of the flower, making it unable to accept any pollen. One last possibility is the tree getting too much nitrogen fertilizer.

To contact Ron Smith for answers to your questions, write to Ron Smith, NDSU Department of Plant Sciences, Dept. 7670, Box 6050, Fargo, ND 58108-6050 or e-mail ronald.smith