October 14, 2004

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: This is my first year trying to grow zucchini, so I have no idea when it’s ripe. I’ve tried to research zucchini online but all I get are recipes. (e-mail reference)

A: Zucchini does not need to ripen. In fact, zucchini tastes better if eaten before it reaches full maturity. Allow it to reach a desirable size for your taste and harvest. The more you keep them picked, the more they will produce. Soon you will have enough zucchini to take care of half the town!

Q: My crabapple tree is loaded with fruit and appears very healthy. Initially the fruit is clean, however as the fruit starts to grow, small black and/or dark brown spots start appearing on some of the apples. As the season progresses, these spots appear on most of the apples. The spots penetrate about an eighth inch deep into each apple, but don’t seem to affect the overall quality of the fruit. Is this apple scab, black rot or insects? I can’t believe insects could be so industrious that they could bore into hundreds of apples in such a short period. Also, you mentioned making apple sauce with crabapples. How do you core them or don’t you bother? (e-mail reference)

A: It is apple scab. It doesn’t affect the eating quality of the apples, just the aesthetics. Making applesauce is something my wife does with our dolgo crabapples. I am the beneficiary of her efforts, so I won’t attempt to tell you how to do it. You may want to contact someone in food and nutrition at NDSU and have them send you instructions.

Q: We planted a red maple in our backyard last fall. The tree has done well until now. The leaves started turning red and are now falling off the tree, especially at the top. My husband took a sample to the nursery where we purchased it. They said it has been overwatered. We have received a lot of rain this year, but have not watered it when it has rained. Our backyard is on a hill, so there has not been any standing water around the tree. Will our tree die, or will it come back with drier weather? (e-mail reference)

A: The nursery made a quick diagnosis without knowing enough facts. It could have been getting too much water, but it is unlikely from where you say it is located. Another possibility is that it is planted too deep. The root ball should be even with the soil surrounding it, and with no more than about 1 to 2 inches of mulch (if any) around that area.

Q: I hope you can help me with an azalea plant problem. Buds will form and they appear healthy, but then they start to turn brown and eventually dry out. The buds are very brittle when I touch them. The leaves around the bud are healthy and the plant continues to grow normally. The plant is very healthy and big. People that see it comment on how beautiful it is. It was full of blooms when I purchased it, but when it bloomed again there were fewer flowers. Now there are no flowers, just dried out buds. (e-mail reference)

A: Dried out flower buds could be a disease known as botrytis or an insect known as thrips. The symptoms are the same. If you are watering overhead, quit and see if that helps. If not, then it is likely thrips. These are very minute insects that get under the flower bud scales and injure the plant tissue with their feeding activity. These are pests that cannot be eliminated, but hopefully can be controlled somewhat. Spray the developing buds with Orthene or Sevin and again 10 days later.

Q: Every morning we come downstairs to find slug trails all over our living room carpet and floor! They only appear in the living room. We took out all of the furniture to find out where they are coming in, but can’t find any holes or slugs. How can we get rid of them and how are they getting in? What germs do they carry with them? We have an 18-month-old daughter who crawls around on the floor. (e-mail reference)

A: Contact a professional pest exterminator and/or your landlord and tell them of the problem. You could put some cheap beer out in shallow dishes with runways to allow them to crawl in the dish. Slugs are attracted to brew. They drown in the beer, but do not get drunk! When you no longer collect slugs in the morning, you have completed your job. You need to find out how they are getting in. An exterminator can put down a border treatment that will prevent this from happening. Slugs do not have any more germs than humans do. They do not harbor disease and in some cultures are considered a delicacy.

Q: My hollyhocks have been beautiful and are about done flowering for the year. Can I cut them back now or do I need to let them go to seed and die back naturally? (e-mail reference)

A: You can do either. If you want them to reseed, allow them to stand. Cut them back if you don’t.

Q: My petunias are getting really spindly looking. Is it too soon to cut them off? If I do cut them off, how far down the plant can I cut without killing it? (Ellendale, N.D.)

A: Cut them back to a leaf node and give them a shot of Miracle-Gro at the same time. If they are getting spindly, they might not be getting enough direct-sun.

Q: I’m having a lot of trouble with web worms. I’ve tried spraying with different insecticides, but that doesn’t seem to kill them. The tree has developed only a few blossoms for the last several years. It is approximately 15-years-old and hasn’t grown much. (e-mail reference)

A: In the spring, selectively prune the tree and spray it with a lime-sulfur and dormant oil spray. Follow that up with a spray at bud break with Sevin or Malathion and again 10 days later.

Q: I have three well-established nanking cherry trees. I want to plant them in a different area because they have taken over the spot they are currently in. Would I kill them if I transplanted them? How do I save them? They are 3-years-old, and this is the first year they have had fruit. (e-mail reference)

A: Wait until they go dormant this fall or do it next spring before they leaf-out.

Q: We have an area on our property that has standing water every spring into summer. It usually dries up in the fall. Can we plant willow trees in this area? Will the standing water kill them? (Carrington, N.D.)

A: No problem if they are the traditional weeping or golden willows. They will love it!

Q: I just had a gentleman come in with a leaf from a begonia. He said it has a powdery, mildew substance on the leaves that is spreading to the other begonias. They are planted on the north side of the house. Any suggestions on what he can do? (Mandan, N.D.)

A: Once the powdery mildew fungus has hit, there is little that can be done except to spray a fungicide on the plants in hopes of keeping it from spreading to new growth and other begonias.

Q: We had a prairiefire crab tree planted in our backyard last year. We were told it was very resistant to diseases, but the leaves are turning brown and falling off. The tree looks sick. We brought a branch back to the nursery, and we were told that the tree has been infected by spores from the arborvitae in our area. Can this be true or are they just trying to get out of replacing our tree? (e-mail reference)

A: Nice try, but it won’t work. They are probably thinking the problem is cedar-apple rust and the arborvitae is the alternate host. The alternate host to cedar-apple rust is the juniper, not the arborvitae, which is an entirely different species. There could very likely be some junipers in the area that are acting as the alternate host for this disease. If they are on your property, you can control that quite easily. It’s a problem if they are on someone else’s property. This disease can be controlled with a good spray program. Use lime-sulfur in early spring while the tree is still dormant. Use a Bordeaux mixture as the new leaves unfold, and again 10 days later.

Q: I have five pruned lilac trees gracing a walkway in my front yard. One is a bushier and much larger variety than the other four. When is the best time to prune them? Also, when should I cut back flowers that are done blooming? (e-mail reference)

A: The best time to prune any flowering plant, assuming the fruit or seed is not wanted, is immediately after flowering. This would include your lilacs and peonies, as well as any other herbaceous plants. Often, timely pruning will result in re-blooming of the plants in the same season.

Q: We bought a new home that came with two apple and two pear trees. They are about 15-years- old. One pear tree has a few pears on it and looks healthy. The other tree has a lot of dead branches and some brown fuzzy clumps on its bark. A few leaves look a bit spotted also. I’m wondering if it has a fungus, some type of disease or is just dying. The lady we bought the home from said she always canned about 20 quarts of pears from the two trees. (Enderlin, N.D.)

A: From what you have told me, I would advise cutting down the sickly tree and hope the healthy one stays that way. In my experience with pear trees, if you have one that is producing for you, do all you can to keep it healthy and consider yourself lucky. More of them die because of disease and soil pH problems than survive to produce fruit.

Q: I planted three yucca plants 25 years ago. They have blossomed into about 20 plants that all flower. I want to give some away. What is the best way of separating them, how should I do it and when? Also, I have a cherry tree that fruits every summer, but has put out runners in the yard. What can I use to kill the little plants but not hurt the grass or garden? When is the best time to separate and transplant peonies? (Valley City, N.D.)

A: Yucca can be replanted right now or any time the ground isn’t frozen. About the root suckers coming up from the cherry tree, the only thing you can try is some RTU Sucker-Stopper. It is available in Bismarck at Cashman’s Nursery. The suckers will drive you crazy before you get them under control. As for peonies, late-summer or early fall is the best time for division and transplanting. If you miss this opportunity, I have had some success with early-spring efforts.

Do you have a gardening or houseplant question? Write to Hortiscope, Box 5051, NDSU Extension Service, Fargo, ND 58105 or e-mail to Ron Smith at ronsmith@ndsuext.nodak.edu. Note to e-mail correspondents: please identify your location (city and state) for most accurate recommendations.

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Source: Ron Smith, (701) 231-8161, ronsmith@ndsuext.nodak.edu
Editor: Rich Mattern, (701) 231-6136, richard.mattern@ndsu.nodak.edu

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