June 21, 2001

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: I noticed that several of my favorite Monardas have blackish/brown areas on the leaves and those leaves are dying. What is this and what do I need to do to get rid of it? I would hate to lose these plants. Also, I was reading in an NDSU brochure that the herbicide Confront is very effective against clover and other broadleaf weeds. I have never seen this product in the stores. Is it available to home-owners? The last few years I have had very few tomatoes due to leaf diseases that totally kill the plants. I want to control it this year and would like to know what product I should buy and when should I start applying it. ( Barney, N.D.)

A: It sounds like a fungal disease on your Monardas, but I don't know what disease without examination. Bordeaux mixture is a good broad-spectrum fungicide. Give it a try and see if you get any control. Confront is not available to homeowners, only to lawn care applicators. I suggest going for the AAS winner tomato varieties that are more disease resistant and plant them in a different location. Also, try to avoid water splash on the foliage; use a drip irrigation system if possible. You can use a fungicide containing chlorothalonil, repeating every seven to 10 days until harvest.

Q: My clematis is 4 years old with large purple flowers. This year I found one of the flowers was variegated with purple and green... very beautiful. I would love to know if I propagate this stem, would it come out this variegated color, or the purple? What would have caused this to happen. I would not be disappointed if all the flowers turned like this. (E-mail reference)

A: This is likely a somatic mutation called a chimera. Many new crops or varieties have been introduced this way. I would encourage you to propagate it vegetatively - via a cutting - and see if it is carried through on the new propagule. If so, then you have discovered a new variety to introduce to the rest of the world. A local nursery may be interested in purchasing it from you for royalty payments or an outright payment.

Q: I have a question regarding spider plants. Do the white stripes on the leaves photosynthesize? (E-mail reference, Chicago, Ill.)

A: Yes. The chlorophyll is simply masked by the white tissue, but it is carrying on the process anyway. Just witness how well they grow under relatively low light conditions - a testimony to their efficiency.

Q: I have a beautiful hybrid hydrangea plant, the ones that have the ruffly, beautiful leaves. The blooms are just gorgeous and dark pink. I wouldn't change it at all, but I have one of the older types like Mom used to grow about 5 feet from it. The pink flowers are washed out in color. My old friend added something to the soil and changed hers to purple, and Mom could change hers from pink to blue, by adding something. Do you know what I can do to change my faded pink hydrangea to purple or blue? (E-mail reference, Louisiana)

A: You can make the colors on a hydrangea move by using a sulfur-based fertilizer like aluminum sulfate to get the purple/blue color and lime to get the pink color.

Q: My plum trees are infected by something that causes tiny green tubes to form on the bottom of the leaves. What can I do? (Sioux Falls, S.D.)

A: Not to worry. They are likely galls formed from insect or mite feeding or egg laying activity earlier in the season. If you pick one of them apart, you may see a small white or tan grub inside.

They cause no serious harm to the tree, just aesthetics, and it isn't worth trying to spray for.

Q: I was checking out your website and noticed someone sent you a question about an old Sheepsnose apple tree. This is an actual variety, as I have successfully grafted a scion this spring here in Kelowna, B.C., Canada. I got the scion from my dad, who has it growing in his yard here in the Okanagan Valley as well. He obtained his scions about 15 years ago from his hometown of Hildesheim in Germany. It is a European variety. In German it is called Prinzenapfel, and the term Sheepnose is used in the British Isles. I could obtain scion next winter for that person who wrote to you if interested. (E-mail reference, Kelowna, B.C.)

A: I'll see if your letter draws a response when I publish it. If it does, the two of you can communicate with each other directly.

Q: I am looking for suggestions for a backyard shade tree that will be fast growing and provide some nice fall color. Recently I planted an Autumn Blaze maple and would like something that will complement it. I also plan to plant an Amur maple hedge and a weeping willow. Any suggestions? ( Bismarck, N.D.)

A: How about an 'Autumn Splendor' Ohio buckeye?

Q: We live in a new development and are looking at trees to put in -- one in the front yard and a few in the back. I am wondering about a "nannyberry." How big does it get, is it hard to grow, is it a slow grower and are the flowers and berries messy? We don't want messy fruit in the fall. (Grand Forks, N.D.)

A: You needn't worry about the nannyberry fruit. It all gets eaten by the birds before it ever has a chance to become messy. It gets 18 to 20 feet in height with a spread about 10 feet and a beautiful fall color. I highly recommend it!

Q: I have two Japanese crabapple trees that I bought two years ago as very small trees, Now they are about 9 feet tall but this year had no blooms on either of them. Do I need to fertilize them or prune them to get them to bloom? I am very new to this and want them to bloom next year. (E-mail reference, Sacramento, Cal.)

A: Not needed. The lack of blooming is more likely related to weather conditions than it is to fertilization or pruning. I would suggest contacting your local extension horticulturist at UC and asking for a publication on care of crabapples in your region.

Q: I planted dahlias this spring. They came up real good but now they look wilted. I planted them in plastic patio pots with potting soil. What could be the problem? (Barnesville, Minn.)

A: The problem could be poor drainage or a vascular rot that has developed.

Q: My poplar tree is about 3 1/2 feet in diameter and 50 to 60 feet tall. I don't now how old it is but It was here when I moved in 15 years ago and it was tall then. It is the type of poplar that sheds sticky seeds in the spring. The tree appears healthy but my neighbor is concerned that it needs to be pruned? Can you help us out here? (E-mail reference, Winnipeg, Canada)

A: Poplars are noted for their weak wood and possible limb fall. It is a good idea to get a qualified arborist out on a regular basis to have the tree inspected and pruned to get the deadwood out, at the very least, and remove any limbs that may be potential problems later in the season.

Q: I have a Swedish ivy that continues to flourish, but the older leaves turn purplish with deep purple veins while the new leaves are the pretty shiny green that I would expect. The plant started out as all green. Am I doing something wrong, and how do I get the plant back to green? (E-mail reference)

A: The first thing I would suggest is fertilization, since you didn't mention it. Schultz makes a very good "Plant Food" (10-15-10) that houseplants typically respond well to. It is in all popular garden center outlets.

Q: I'd like to renovate my lawn. It is full of crabgrass and dandelions, among other things. How do I go about getting this lawn back into shape? (Grand Forks, N.D.)

A: Kill everything off with Roundup; mow short ( VERY short), collect clippings, power rake, seed, drag in, fertilize, water. Then wait, and by this fall you should have a decent lawn--with some weeds of course, but they can be easily controlled after the third to fifth mowing.

Q: I built a flowerbed in one corner of my yard, against two fences. I enclosed the bed with wooden rails. The neighbor has a wood pile on the other side of his fence, so the grass grows and no mowing or trimming is done in that corner. What can I do to keep the grass from taking over my floor bed without hurting the flowers I am trying to grow? Would the enclosure keep spray from affecting the flowers if I spray the grass? ( Fargo, N.D.)

A: In a word, yes! Just be sure to do it when the wind isn't blowing.

Q: I'm not much of a gardener, but I am curious about the red edges on my jade leaf. Does that mean it's getting too much light? (E-mail reference)

A: It could be the beginning signs of poor drainage, keeping the soil too wet, or a salt build-up in the root zone.

Q: I recently bought my mother a "Hoya Bella" plant but unfortunately the description of how to care for this plant was missing. Could you please tell me the needs of this plant? (E-mail reference)

A: Average temperatures, bright light--even direct sunlight on occasion--water liberally except in winter, mist leaves when plant is not in bloom (use distilled water). If repotting is necessary, do so in the spring.

Q: I have noticed my poplar trees ( I don't know what kind they are) haven't leafed out fully. On some branches there are leaves and on the rest of the branch the buds seem to be dead. Last year the trees had a blight. Some of the leaves had turned color to a orange/yellow (like leaves in the fall). Do you know what could be wrong and what I can do to help the trees? I'm sorry if my explanation is so vague, but I don't know how else to explain it. ( Battle View, N.D.)

A: The poplars are noted for their problems, mostly branch cankers. Once the canker has set in, little can be done about it except to prune out the affected branches at least 6 inches beyond the visible canker area. Depending on the canker development, stimulating growth may help to control spread by compartmentalization from the vigorous growth. Unfortunately, no sprays have proven effective.

Q: I have a beautiful, fragrant, old fashioned mock orange bush that has a grapevine growing in the middle of it. The woody stem of the grapevine is very similar to the canes of the mock orange bush in the area near the ground. It is only when the grape vine reaches out over the top of the bush that I can see it. I have pulled it back year after year, and last year I gave up. I pulled the vine over to just one corner so I could keep it under control, force it into one direction, and keep it from spreading all over the canopy of the bush. Do you know of any herbicide that I can use to kill off this grapevine that will not kill the mock orange bush? (E-mail reference)

A: Cut the vine off at the stump, and carefully paint a solution of Roundup on the cut stump where it will hopefully translocate and kill the plant--eventually. Any sprouts that come up, paint them as well.

Q: Can you tell me what is wrong with my Norfolk Island pine? It keeps losing branches and I am not sure if I am watering it too much or not. (Carrington, N.D.)

A: It is possible that your Norfolk Island pine is receiving too much water; however, branches are usually lost when the plant is allowed to dry out or when it is located near a heat vent or other source of hot, dry air.

Q: I would like to know what kind of vine the enclosed sample is from and if it would be okay to bring it into North Dakota. (Jamestown, N.D.)

A: The plant is known as Virginia creeper. It is readily available at most garden centers in North Dakota, and it thrives!

Q: I have two questions for you. What is the enclosed plant? I also have a problem with potato bugs. What can I do about them? (Jamestown, N.D.)

A: Congratulations! You have now joined the legions of gardeners who have ground ivy (Glechoma hederacea), a member of the mint family that is quite invasive. Get rid of it as you see it, or it will overrun your entire garden. You are smart to get a jump on the Colorado potato beetle. Spray the crop with Bt as it grows throughout the season. This is an organic control that does not leave any residue on the tubers. You will have to spray every 10 to 14 days to be effective.

Q: I have enclosed two samples. One is a cotoneaster found in a hedge. There is about a 12-foot section that has not gotten leaves this spring and appears dead. What are your suggestions?

The other sample is from a 12-foot spruce tree in a shelterbelt near the house. Some of the needles on it seem dry and brown. A few of the trees are this way. Is that normal? If it isn’t, what can be done? (Bismarck, N.D.)

A: The cotoneaster was covered with oyster shell scale, which was likely a major contributor to its death. The spruce buds appear healthy and the new growth seems vigorous. From the sample you sent, the damage appears to be mostly environmental, rather than pathogen caused.

Unfortunately, this problem is widespread across the region which, could technically make it normal, but not desirable. Since nothing can be done about it, be happy that the new growth looks so good.

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: Gary Moran, (701) 231-7865, gmoran@ndsuext.nodak.edu