October 25, 2001

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: I'm an uneducated tree lover with three ashes in my yard in Colorado at an elevation of about 6,300 feet. Because of the elevation (and the foothills microclimate), my trees are subjected to late frosts. This year's was especially bad, hitting right after the Patmore and Autumn Purple (both about 5.5-inch trunk) leafed out. The frost completely killed off all the leaves. The Patmore (planted in a lawn) has struggled back with about 30 percent leaf coverage, but the Autumn Purple is failing. It put out perhaps 20 percent leaves, though very small ones. They are now browning atop the individual leaf stems and then turning brown. Also, the Autumn Purple pushed up numerous suckers around the base. My front yard ash has a few leaves turning yellow, and I was told this is due to overwatering. The tree is in a lawn and the watering amount hasn't changed over the past three years. The Patmore in the back and the ash in the front both show signs of borers, but I failed to notice early enough to take action against the pupae. I will be vigilant next spring! I realize a leaf sample would be far more descriptive, and can send if necessary, but from this description, can you ascertain what approach I might take to save this beautiful backyard neighbor? (E-mail reference, Colorado)

A: The prognosis doesn't look good. If it were just the frost damage, I would say no problem, as trees of that trunk size can survive occasional nips by Jack Frost and recover nicely the next year. But, since you have indicated the borer problem and the suckers coming up, this indicates the trees are under a lot of environmental stress, and might not be long for this world. If the threes are worth it to you, have a qualified arborist come out to make an assessment for you. Undersized leaves on a re-leafing is normal; borers and suckers are not. An aroborist could see the situation they are in and advise you far more accurately than I can at this distance.

Q: We planted bare root trees this spring. Is there anything special we should do to prepare them for winter? Should we continue to water them up until frost or longer? Also, when can grass be seeded this fall? (Aberdeen, S.D.)

A: Keep your trees watered until they are defoliated. This doesn't mean daily watering, but do not let them go into the winter months dry. Yes, grass seed can be sown this fall. Starting around Labor Day weekend is an ideal time to carry it out.

Q: I have a beautiful white oak in my back yard that appears to be suffering. The bark is splitting near the base, and I have numerous white growths with reddish stripes on the backs of the leaves near the base. They appear to be insects. I've not seen this anywhere before. Any suggestions? (Bemidji, Minn.)

A: What you are describing sounds fairly normal. The tree will have bark exfoliate at the base as it grows and matures; the leaves are frequently attacked early in the spring by mites or small insects that lay eggs in the unfolding leaf tissue that causes gall growth, which is often noticed at this time of year. These are typically nothing to worry about, and they go in cycles, without harming the tree. No action is warranted, and would be useless at this time anyway.

Q: I would like to hear your recommendation for kochia control in turfgrass. Do you see damage from Starane use or should you just stick with something like Banvel. (Hettinger, N.D.)

A: I don't know what Starane is, so I cannot pass judgement; Banvel should do the job without being a problem on turf.

Q: I've tried to grow pumpkins before with no luck. This year we planted a few again (purely for fun - no large quantities or for selling) and I'm having the same problem. The vines produce an abundance of male flowers but very few females. The females that do appear fall off before the flowers even open. I've read that it's probably due to lack of pollination, so I wanted to hand-pollinate them. I went out in the morning as instructed and found ready, open male flowers, but the female flowers were tightly closed up with no access to the lobes that I'm supposed to transfer the pollen to. Any ideas? (E-mail reference, San Jose, N.M.)

A: I don't know why the female flowers are not opening. Where did you get the seed? It could be a variety (cultivar) problem where your day-length, temperature extremes, or sunlight intensity is not conducive for reproductive activity. It may also be a fertility problem: pumpkins are greedy feeders of nutrients, but an imbalance of too much nitrogen could cause problems as well. Or, since reproduction requires an outlay of energy, perhaps the female flowers are not opening or aborting because they are grown in partial shade and simply have not accumulated enough carbohydrate reserves to develop pumpkin fruit. I would suggest getting the soil tested for nitrogen, phosphorus, potassium, soluble salt levels, pH, and organic matter content. Also, check to see what the amount of direct sunlight contact with the vines are. They need full sunlight to be productive.

Q: I planted two purple leaf plum bushes, one in 1997 and the other in 1998. They are about 10 feet apart and receive about six hours of full sun. The tree planted in 1998 has grown to about 15 feet tall and 10 feet wide. This year the top 2 feet of this bush is dark red and the rest of the leaves are dark green. What would you do to encourage red leaves? (E-mail reference)

A: Nothing. They will turn red based on the maturity and genetic make-up of the tree. You might try taking 6 to 9-inch tips of the red-leaf branches and see if you can root them, and if so, whether or not they will produce all red leaves.

Q: I would like to purchase a American linden but I am not sure of the cultivar I am looking for. I first saw the tree when it was planted along the entrance and around the driveway where I work and fell in love with it. I found out it was a linden by taking a leaf to the garden shop. They did not have any of the trees in stock. The trees where I work are short and they grow in a shape like the dogwood. You wrote that there are many cultivars of the American linden on the market: Boulevard, Dakota, Douglas, Fastigata, Legend, Lincoln, Redmons, Rosehill and Sentry. Could you tell me which one I am interested in by the description I gave you? If I can't find the one I want around here, is it a good idea to mail order for one and if so where can I order it from? I would love to have that tree! (E-mail reference, Fort Washington, Md.)

A: The closest I can come to making a recommendation based on what you have told me are either the 'Dakota' or the 'Rosehill,' which do not grown in the upright or pyramidal shape but with more of a rounded, open crown that is roughly reminiscent of a dogwood tree. As far as ordering from a garden catalog, I advise against it for shade trees. For seeds, perennials, fruit trees, exotics, etc. the catalogs are usually fine. I would suggest that you contact the Maryland Nurseryman's Association (should be able to get their number from a local garden center or nursery) and ask where they could suggest getting such a tree. If you get no satisfaction from that route, then I suggest making contact with their counterpart in Pennsylvania. They have a huge, functioning organization. I share your love for Lindens. I have one (Redmond) planted in my front yard.

Q: I have a plum pit. How do I grow a tree from it? I am a CPA, not a horticulturist, so please help! (E-mail reference)

A: The easiest way is to plant the pit about 2 or 3 inches deep where you want the tree to grow. It will go through winter stratification and scarification and, if the seed is viable, it will germinate and grow into the tree of your plum-producing dreams! Just make sure you plant it in an area where it can grow into a tree, with plenty of sunlight.

Q: I have a lilac bush that is 8 years old. I have recently moved and would like to move it to my new house. What would be the best time to do it and should I prune it down before I try? (E-mail reference)

A: An 8 year-old lilac bush is going to have quite an extensive root system, so I hope you have a strong back! Wait until it goes dormant this fall, then cut it back as far as possible. To dig it out, I would suggest splitting the rootball, and moving the plant in two parts, planting the parts in different locations at the new location. Water in well. Next spring there should be a flush of vigorous growth that will be your new lilac. It will not flower that year but should in subsequent years.

Q: We recently bought an 11- year-old house replete with several silver maples in the front and back yards. The roots running across the ground make it difficult to mow. Is it safe to cut the exposed roots? I assume that the trees are around 10 to15 years old. (E-mail reference, Huntsville, Ala.)

A: The exposed roots help to anchor the tree, but usually the silver maple is not short of roots, so those intersecting the surface can be cut back. Usually if a tree is going to windfall it will do it no matter how extensive the root system happens to be. I'd also suggest getting some of the canopy thinned out to reduce the exposure and resistance to wind forces.

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