August 2, 2001

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: What kind of fertilizer do I give my Calla Lily and how often? When I dig it up for the winter months, do I water it like normal? Keep it in the light? (E-mail reference)

A: We need to consider where the Calla is found in it's native habitat, which happens to be a swampland. In the late summer months, the swamp dries up and the foliage dies down, which you should allow it to do late each summer. Water it only to keep it alive, allowing the top half of the potting mix to dry completely. When new growth begins again, increase watering and fertilize once a month with a flowering house plant type fertilizer. Give the plant bright indirect light, along with some sunlight when it is in full foliage. When dormant, you can place it outdoors in full sun, as long as there is no danger of frost or rainy weather.

Q: We had an old American elm that died from Dutch Elm and maybe some other diseases. We have an offspring of that elm. Can it catch any diseases from the roots of the old tree even though it’s dead? (E-mail reference)

A: There is every possibility, but I think it is worth the risk.

Q: Any advice on why the acorns on our oak are falling in early July? The nuts are premature, barely formed inside the caps, but they're dropping by the dozen each day. (E-mail reference)

A: If you open up one of those acorns, you will probably find a small white grub, or evidence of past presence via the exit holes, that are or have been feeding on the acorn meat. If the nuts appear sound and are not hollowed out by this borer, then it could be just superfluous nut drop from too heavy a crop. In either case, there is nothing you can do about the situation at this time.

Q: I am looking for some good mail order companies to purchase American linden/basswood trees. (E-mail reference)

A: When it comes to making a purchase like a Linden tree, I am against shopping via mail order catalogs. You are much better off going to a local nursery or garden center and making a selection for yourself. You will pay more, but you will get it back in spades with quality and guarantees from the local nursery.

Q: Our new house has an ash tree in the backyard. The tree took a long time to leaf this spring. Now all the leaves have wart-like projections up to about a quarter inch tall. There are about 10 on each leaf. What can we do to help this tree? ( Dickinson, N.D.)

A: Just be patient. Those are harmless galls that have little or nothing to do with the late leafing of your tree. They likely will not be there next year. Depending on the age of the tree, I would suggest fertilizing it so it will come forth next spring with a little more vigor.

Q: My tulips did real well this year. I have done as you are supposed to and let the leaves dry up undisturbed. I notice several of them have produced seed pods. Can I harvest the seed and grow it in the hope of a new color? If so, when and how do I go about harvesting them? ( Jamestown, N.D.)

A: Simply collect the seed and scatter them where you want them to grow in barely disturbed soil, lightly cover with soil, and see what comes up. I have never done this, but from what I understand, it takes about three years of growth to produce bulbs of decent size that will produce flowers.

Q: Help! The grackles, crows or black birds of some sort are mutilating my marigolds. They're pecking away at the flowers until there are hardly any left. Any suggestions? (Fargo, N.D.)

A: Every year someone asks me about these characters attacking their marigolds, and all I can say is that they are the mischief makers of the bird world--rampageous, rambunctious, ridiculers of our efforts to have nice plantings! The "Scare Balloon" works to keep them away. Local nurseries have them. The birds think it is an owl or some other bird of prey and it usually gives them quite a fright. They'll have to find someone else's marigold plantings to harass.

Q: I would like to plant a perennial flower garden on the north side of a farm building. I would like to plant a hedge in the back of the perennials to provide a background for the flowers and to add some height. Will the roots from the hedge interfere with the flowers? I would like to plant a dwarf burning bush, which should grow to 4 to 6 feet tall and is advertised as good for zones 3 to 8. (Spiritwood N.D.)

A: Your idea is carried out all the time with minimal problems from the hedge roots, especially the Euonymus you will be using. Go for it!

Q: What can I spray on my evergreen trees to get rid of spiders? (E-mail reference)

A: Believe it or not, a hard spray of water on a weekly basis will do as well if not better than any pesticide that I can recommend.

Q: This is the third season for my hydrangea. For three years the flowers have come up but will not flower. Last year the nursery I purchased them from suggested cutting them back, which I did, and still the same results. They said fertilization on my lawn produces too much nitrogen. I don't fertilize my lawn. I live in the country with no neighbors, so nothing there either. They are on the north side of the house, so now they are telling me it's too shady. They sold me these because it was the north side of my house. They say too much water, not enough water, blah, blah, blah. Seven big beautiful plants, three years invested and no blooming. Help, please. (E-mail reference, Iowa)

A: Annabelles bloom their beautiful heads off all over North Dakota and I see no reason why they shouldn't do the same thing in Iowa! Possibly they are in too much shade. While they will tolerate some shade (mine are planted somewhat on the north side of our house too), if they don't get some sunlight during the day, their blooming will be very poor or in your case, non-existent. They also like to be kept moist--not wet--and bloom on new wood, so pruning in late fall or early spring right to the ground will do the trick. If they fail to bloom after this, I suggest moving them to a sunnier location. Anticipating your next question, here is a brief list of some shade tolerant shrubs that will grow in Iowa, as well as all over the upper midwest: Amur maple, serviceberry, many species of dogwood, bush honeysuckle, pin cherry, scarlet elder and viburnums.

Q: I have horseradish taking over my garden plot. I have nothing planted this year, and tried roundup on it, but that didn't take care of it. Is there something that will kill these plants? (Cavalier, N.D.)

A: Yes--blacktop and concrete! If that is too drastic, try TRIMEC with a spreader-sticker. If that fails, then rent a flame-thrower! They are tough customers to get rid of, and perhaps the only way is to dig them out.

Q: I was interested in your comments regarding aluminum sulfate and lime for colors of hydrangea. Is it too late to apply now ? Do we buy these fertilizers at a nursery or are they available at discount stores? Also, do your simply apply around base of plants and water in? (Detroit Lakes, Minn.)

A: The applications are more effective if applied prior to new growth beginning, and they are materials that one usually can obtain at local garden centers or supply stores. As a rule of thumb, a heaping tablespoon of lime sprinkled under the canopy and watered in, and a tablespoon of the sulfate per gallon of water and watered around the soil will do the trick. If not, then add a little more until you get the coloration you want.

Q: It got too hot for my newly planted grass. If I re-seed and I cover it with grass clippings this time of year will it have a good chance of making it? My daughter also planted new seed this year and she has one location in her yard that is yellow and never grows. the rest is doing really well but this one spot doesn't straighten out. Also, my father-in-law is deep into tomatoes and his plants are huge. He says he has little red bugs or maggot type things eating the leaves. What should he do and what are they? (Lisbon, N.D.)

A: Covering the emerging grass with grass clippings might not be a good idea with hot wether, unless you spread them out to dry first on a pavement or patio before spreading on the lawn. I'm willing to make a small bet that your daughter's yellowed lawn is due to a low spot that collects salts and is poorly drained. She can topdress or at least core aerate before reseeding.

Your father-in-law’s tomatoes are probably being eaten by potato beetles. Spray with Neem or pyrethrin, both of which are used in organic gardening and are effective in controlling them. Expect to have to do repeat sprays. Both are safe to use around humans.

Q: I have an old large mountain ash that seem to have had something feeding on it. There are shells left stuck to the smallest branches with part of the shells being round, shiny and black. The leaves on those branches are just stripped down to almost nothing. I can tell the feeding took place some days ago as nothing is there now doing any feeding. I think the tree may have a touch of fireblight also. (E-mail reference)

A: Sounds like the perfect description of the pear slug sawfly. With warm weather, we are liable to have a second generation this summer. Insecticidal soaps, summer oils, Sevin, etc. will take care of them when they are present. Usually the tree is not seriously hurt, it just looks ugly!

Q: Can you please tell me how to get rid of orange common day lilies? They are taking over my blueberries, ground cover, and grass. Is there something I can spray with to get rid of these pests? (E-mail reference)

A: I am sorry to hear these beautiful flowers that help hold the soil against erosion and grow under a wide variety of conditions called pests. But I agree that they are difficult to control and spread with a vengeance without any encouragement. Being lilies, they will be tough to control, and digging may be the only answer if herbicides don't work. If digging is needed, hire it out to a young person and supervise them to make sure they get ALL the rhizomes out of the beds! Herbicide suggestions are Roundup with a spreader/sticker added or TRIMEC, following directions for broadleaf weed control.

Q: I have several crab apple trees, all are about 40 years old. They continue to bloom every other year but need to be trimmed. What is the best time of the year to trim. (E-mail reference)

A: The best time to trim is in the early spring, when the trees are still dormant. Trimming now would predispose the trees to disease entry, especially fireblight, so it is not recommended during the summer weeks unless necessary to prevent breakage or to correct a hazardous situation.

Q: Our home was built about 6 years ago in a wooded subdivision. Just this year, in the area of our basswood tree (at the back of our yard and includes our yard and our neighbor’s), we have groups of one to eight plants coming up in our lawn. The ones that I have dug up are attached to roots or can be in a large clump with a thick deep root system of their own. We have cut the lawn area short hoping they would die, but they come back. We have also sprayed them and it didn't seem to do anything. Can you tell me if this has anything to do with our basswood tree, and if not can you send me in the right direction to eliminate this problem? (E-mail reference)

A: I doubt that it is the basswood tree causing the suckering, unless the leaves on the suckers you are digging up are identical to the ones on the tree. Since your home is in a wooded area, it is highly likely that trees were cut down to make room for yours and your neighbor's houses. In doing so, parts of root systems were left behind, some of which have the ability to send up new growth from those root pieces. Poplars, cherries, lilacs, and willows are just a few of the species that are known for this characteristic. The only thing you can do is what you are currently doing--dig or spray with herbicide. Eventually you will prevail, so hang in there!

Q: I need help with my apple tree. Every branch is loaded with apples and I was thinking of cutting some of the lower branches off, thinking this would help with the other branches. Years past I would have to prop up the lower branches with 2x4s.So would it be all right to cut those branches now? (E-mail reference)

A: Not a good idea. Pruning now would open the tree to a host of fungal, bacterial, and virus disease problems. Prune the tree early next spring when it is still leafless (dormant). In the meantime prop up the heavy branches with your 2x4s!

Q: I have a what I call a snowball bush. It is 5 to 6 years old about 6 to 7 feet tall and about 7 feet across. It came from a sucker off my sister's tree. It's growing under my ash and box elder trees. It's healthy and growing great, but has not produced the snowball flowers that my sister’s does. It flowers in a white cluster about the size of a baseball. My sister’s bush is growing in the same environment. Any ideas of what it might be and why it's not flowering? ( LaMoure, N.D.)

A: Sucker growth is seldom the equal of the original plant because most plants are grafted to a different cultivar rootstock. This results in something growing that vaguely resembles the parent, but not entirely. People are continually doing this with flowering trees and shrubs, especially roses. They are better off taking scion or budwood cuttings, not anything from a root sucker, to get a copy of the original plant. Even then, some characteristics may be lost, such as vigor or winter hardiness.

Q: I noticed several people asked you for tips on how to dry hydrangea blooms. Might I humbly offer a suggestion? I have found that it is best leave the bloom on the plant itself until the flowers begin to fade and look as though they are drying out. If you pick them earlier when they are at their brightest and freshest it seems to cause them to wilt and shrivel up very quickly. I don't know why this is, but time and again I have lost flowers I wanted to dry for cutting them too early. With patience I have been able to create beautiful dried arrangements. Also, it is not necessary to hang them upside down as you would a rose. Roses are hung that way to insure a straight stem when completely dry, but hydrangea stems seem naturally stiffer. You can just put them in an empty vase and let them dry on their own, they will hold their shape if they weren't cut too early. (E-mail reference)

A: Thank you for your humble suggestion! I am sure the readers of the column will appreciate getting the information first hand from one who has had ample experience.

Q: Can you give me some information on "common American smoke tree seed" and where I can purchase some? ( Fargo, N.D.)

A: The American smoke tree is the Cotinus obovatus, which is common in south-central U.S. landscapes and is closely related to Cotinus coggygria, the common smoketree, which is seen more often in the northern states. There is an outside chance either one could survive in the southern parts of North Dakota, as they are listed as hardy starting in zone 4 in protected locations, but will definitely do better in zone 5 areas. Where to get the seed is a good guess. I would suggest writing to the Arnold Arboretum, 125 Arborway, Jamaica Plain, MA 02130-3519, phone 617-524-1718 or e-mail

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