July 31, 2003

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: We have a raspberry patch that came up by itself quite a few years ago under a fuel oil barrel. The barrel was moved to a new location and the plants continue to grow and spread. However, the plants do not grow berries, only a few single cells on some plants. What can we do to get berries? Do raspberries need a male and female plant to get berries? (Black Hills, S.D.)

A: Raspberries need plenty of sunlight to produce fruit. No male or female plant is involved so, if you don't over fertilize and have it in full sun, it should fruit for you.

Q: I have a question about Ortho Bug B Gone Multi Purpose garden dust. The active ingredient is permethrin. The label indicates that it is effective on bugs, beetles and worms on most garden plants but does not mention green beans. Is it safe to use this product on green beans to control beetles? (Milbank, S.D.)

A: The product is a common and effective insecticide for all vegetables. There should be a general post application time on the label. If not, don't worry about it but be sure to wash your vegetables completely before consumption.

Q: I recently applied Scotts Turf Builder with Plus 2 Weed Control on my front and back lawn. A day later I noticed brown burned spots all over the place. Before that, my lawn was green but had a lot of "dollar weeds" in front while the back yard had some dandelions. Is there anything I can do to get rid of the burned spots? I looked at the directions after I noticed the burned spots and read that I should have applied the fertilizer in the morning while the grass was still wet or after it has been lightly sprinkled. I think the grass burned because I put the fertilizer on dry grass. (E-mail reference)

A: All you can do is water and wait. Forget the combination products because they don’t do as good a job as straight fertilizer or straight herbicide. Next time read the label first; you'll be surprised at what you can learn.

Q: Approximately how many days or weeks does it take for a cottonwood tree to release all its cotton? My house looks like it is ready for Halloween but I don’t want to wash it until we are at the end of the cotton season. (E-mail reference)

A: Most, if not all, should be gone in about 10 14 days depending on the weather and vigor of the tree.

Q: Last night our maple tree was hit by lightening or high winds. One of the big branches was broken and split up the main part of the tree. We trimmed the branch as best we could. There appears to be a black mark on the tree that could be from lightening. Should we put something on the bare part or just let it go? Will it survive? (E-mail reference)

A: I’m sorry to say that the answer is no to both of your questions. If the tree was indeed hit by lightening, it is done for. Some trees show it faster than others.

Q: I transplanted established hybrid roses two years ago to a new fertilized bed, which gets full sun. About half of them budded and bloomed last year. This spring most of the stems budded and it looked as though they would flourish but the buds swelled, turned brown and died. The leaves have tiny holes but I haven't seen any bugs. Can you give me some advice? (Brookings, S.D.)

A: It’s probably thrips feeding on the flowers that have kept them from opening. The holes in the leaves are due to any character that is hungry for a quick bite out of a rose leaf. I suggest cutting the rose buds back to the first 5 leaflet leaf and spraying the plants with Orthene. Being a systemic, it will help control the thrips or any other feeders.

Q: I have a question about hollyhocks. I had wonderful pastel color flowers last year but this year they are all black. I thought hollyhocks were perennials but now I am told they are bi annual. Is that true? (E-mail reference)

A: Hollyhocks are biennials. I would guess the blackness is some sort of fungus.

Q: I have two different crown-of-thorn plants. One bloomed but now seems to be in a rest period. Should I use any fertilizer made for cactus plants? How often should I use it? The other crown of thorns has many stems that are about the thickness of a pencil. It appears to be very healthy and is constantly producing new leaves. It has been forming tiny buds but they dry up and fall off before they can fully develop. I have these plants in a south window where they get plenty of light. I am not sure of the watering requirements so I wonder if they are getting the right amount of water. I’m using a light soil that is recommended for cactus plants. (White Bear Lake, Minn.)

A: A crown of thorns (Euphorbia milii) will require as much light as the south exposure can give. Only fertilize during an active growth phase. Fertilize at half strength every two to three weeks after that. Flowers will be produced on new growth. Wet the entire root mass during active growth but allow the top inch to dry between waterings. After flowering, allow the top third of the soil mass to dry before watering. If the soil dries completely, the leaves will drop prematurely. A crown of thorns is a fickle plant to grow.

Q: Potato bugs have eaten most of the leaves on my potato plants. I have them under control now but will I still get potatoes from these plants? (E-mail reference)

A: Yes, but probably only small ones.

Q: What would be the proper procedure to clean my hand pump weed sprayer after using roundup or using Weed B gone? I would like to use the same sprayer for both. (E-mail reference)

A: Bad idea. Use separate sprayers.

Q: Can you pick and use rhubarb after it has gone to seed? (E-mail reference)

A: Yes, but you should stop picking it now. You should remove the seed head as it is developing. Seed production takes energy away from the vegetative production of the plant, which is what is wanted.

Q: We planted four cedar trees but one now has yellow and brown branches but still some green. Is the tree beyond hope or can it be saved? (E-mail reference)

A: It depends on the extent of damage and whether or not it is caused by a biotic organism or by environmental conditions. If most of the tree has dead foliage, it isn't worth saving. If just a few snippets are brown, then prune them out, fertilize and keep the tree evenly moist but not soggy.

Q: I planted a lilac bush last summer that grew and bloomed nicely. This summer it bloomed but then the leaves turned brown and it appears to have died. That part of the yard has been really wet this year. Could that be the problem? Is there any chance of saving it? Should I leave it and hope that it comes back next year? Should I cut it back? (Fargo, N.D.)

A: Check the cambium to see if it is still green by scraping your thumbnail along one of the stems. If it is, there's a good chance that it will come back next year. If not, then it is likely a goner. Lilacs are tough, but they don't tolerate standing water very well.

Q: I have a cucumber problem. I have straight 8's that are growing fine but the fruits are only about 2 inches long and about as thick as a pencil. They have been fertilized numerous times. Could over-fertilizing be the problem? (Bismarck, N.D.)

A: Back off on the fertilization. They should thicken up as they mature. Straight 8's are extremely dependable at producing a crop. The bees might not have properly pollinated them this season because of our fickle weather.

Q: My husband and I would like to plant roses but I've heard they’re hard to grow. Could you advise me on a hardy rose bush that might do better in our cold Minnesota weather? Do you know where I might find them? When can they be planted? (Crookston, Minn.)

A: I would suggest selecting the prairie (Rosa setigera) or prairie wild (Rosa arkansana) rose as your initial selections if you are a beginning rose gardener. They are native and hardy for the northern climates. If you are not familiar with these roses, they are not at all like the standard roses you may have seen in other parts of the country. The prairie wild rose is a suckering type, cold and drought hardy, and gets about 12 inches tall. Some consider them a weed. The prairie rose can be used as a climber or a bush. It produces single pink flowers in July and attractive rose hips (fruits) in the fall, which help to attract birds to the landscape. Neither of these roses needs special winter protection. The others require extensive protection depending on your location. Your location may require you to use the "Minnesota tip" which means the entire plant is tipped over into a trench and covered with soil before winter. All roses require good sunlight, air movement and decent soil drainage to be at their best. I would suggest visiting a local garden center in your community to see what the local proprietors have to offer.

Q: I have silver maple trees on my boulevard. My neighbor’s silver maples have small clusters of little reddish-green nodules on many of the leaves. Could it be spider mites? (E-mail reference)

A: It’s nothing to worry about, just enjoy the changing sight. The growths are from what are called erythroid mites that were active in the early spring. Their activity has a plant cell stimulation effect on the tissue, which causes the nodular growth. The damage is only cosmetic and there is nothing you can do to control them. Next spring they will very likely be completely gone.

Q: I purchased beta grape plants this spring and planted them in a wind protected area of my garden. I ran lawn edging in a circle around them about 10-inches from the center of the plant and added white rock on top of the soil to help hold in moisture. I put them about 3 feet apart and built a trellis for them to vine up. I gently tied the old branches and stronger new ones with yarn to hold them up. Is this the proper way to support them? Can you tell me the proper way to prune to promote the best fruit for next year? Is it necessary to add any type of fertilizer? (Battle View, N.D.)

A: Get rid of the rocks. They have no purpose and will cause problems as time passes. Replace the rocks with organic mulch such as shredded bark. I will send you a flier on grape care.

Q: Recently I have been finding gnats on my houseplants. Will the gnats harm my plants? How do I get rid of them? (E-mail reference)

A: Gnats are pests more to us than plants. They usually feed on decaying organic matter in the plant's container. They are easily killed with a houseplant spray that contains pyrethrum. Be persistent and you will soon have them under control.

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