June 14, 2001

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: Can you tell me why my 5-year-old lilacs don’t bloom? ( Forman, N.D.)

A: Either too much shade or too much nitrogen fertilizer. If neither fit the bill, then you likely have selected a cultivar whose flower buds are not hardy in our climatic zone. If none of this fits, then I have no idea!

Q: I bought an eastern snowball thinking it might be in the oakleaf hydrangea family, since its leaf looks something like an oak and it turns red in the fall. Can you tell me if it is part of the family of oak leaf or not? (E-mail reference, Missouri)

A: That is the problem with common names. The oakleaf hydrangea is Hydrangea quericifolia. Both this and the Viburnum are often referred to as "snowball" shrubs. You are dealing with two different species of shrubs here, neither of which is bad, and should perform well on your property.

Q: Is there any harm in leaving the white plastic tree wrap coils on our apple trees all summer? Please help resolve this domestic dispute. (E-mail reference)

A: When did I get the reputation for settling domestic disputes? I have a hard enough time managing my own life. Anyway, without trying to make anyone mad, you are better off taking the wrap off during the summer months to allow the bark to dry and develop normally during the growing season. The wrap, even though it expands as the tree grows, could end up being a haven for destructive insects and canker diseases.

Q: I have my wave petunias in hanging pots. My question is how often to water them. I have been watering them every day but I never know if this is too much or not. (E-mail reference)

A: Every day is a good start. Hanging baskets dry quickly and need daily watering. As the season goes on and the root mass takes over more of the soil ball, it is likely that twice daily watering will be necessary, depending on temperature, wind and other conditions.

Q: Two years ago we seeded a small area of our lawn that was patchy. Unfortunately the seed was full of quackgrass. To make matters worse, the seed blew into my perennial garden. I managed to keep it fairly clear last year, but I can't believe all the grass and quackgrass growing among my precious shrubs and plants. Do you have any ideas or tips as to how I can clean up this disaster without wiping out my entire garden? I was thinking of spraying the larger clumps with Roundup and pulling the rest. Am I doomed? (E-mail reference)

A: Roundup, carefully applied, will do the trick. I would go back to the source of the seed and leave a piece of my mind, though, if you are sure that the source of all the quack is from the purchased seed. If the seed came in a sealed container and had a current seed label that stated the species and variety, purity and germination and listed no noxious weeds, you have a case for reimbursement, at least for the purchase price.

Q: Will you please advise me as to the proper watering schedule of Emerald Green aborvitae? I have them on a watering schedule of every other day along with all my other plantings in my yard. Under this schedule, I am wondering if they will be kept too wet, and what the consequences of that might be. (E-mail reference)

A: Unless you have very sandy soil, every other day is way too much water. Once a week until they become established is ample except under the worst conditions of heat, wind, or drought. Once established, they should get along nicely on whatever Mother Nature provides, unless it goes 30 days without any appreciable rainfall.

Q: I have an individual wondering about fruit production in his apple tree. The apple tree is the only one is his yard, is approximately 8 or 9 years old and of an unknown variety. He said they have had bountiful blossoms but no fruit for the last two years, since their plum tree died. I assume the plum tree was doing the pollinating. What I am wondering is what species and varieties of fruit trees would be suggested for him to provide compatible cross-pollination.

This is a apple tree, not crabapple. ( Hettinger, N.D.)

A: No, the plum and apple tree do not cross pollinate. They are different species entirely. Apples and crabapples will cross, and apples and crabapples of different cultivars will cross. Tell your client that another tree like a Hazen or Winter Crisp planted within a quarter mile will do it.

Many times fruit set is poor if the weather doesn't cooperate at critical times. Windy, cold, and wet will prevent pollination every time.

Q: I have a Luscious pear tree that is 9 years old. It is a very healthy tree. Last year was the first year I had flowers on it. The bad thing though is last year we had a freeze when the tree was flowering and lost it all. This year there are many more flowers and everything is looking good.

Does the Luscious pear tree need to be cross pollinated or can it self pollinate? (E-mail reference)

A: Most pear cultivars are self-unfruitful, meaning they need another cultivar to bear fruit. You may get some fruit set without another pear nearby, but it will only be tokenism, not a crop. I suggest a 'Summer Crisp' as the mate to cross with.

Q: I have a spot in my vegetable garden that only gets about five to six hours of sun a day. Is there any type of vegetable that would do all right there? I hate to have all that wasted space. (E-mail reference)

A: Yes, the leafy types: lettuce, endive, cabbage, Swiss chard, celery, and spinach.

Q: Yesterday we had two 16-foot Colorado blue spruce trees planted. They were in the midst of new growth, and that growth has drooped down. We watered them well after planting, and our soil is mostly clay. The temperature last night was in the 50s F. This morning some of the new growth had stood back up, but it drooped back down during the day today. Any suggestions? Should we water them more? (E-mail reference, Illinois)

A: No, don't water them any more, but don't let them dry out either. I suggest getting some Wilt-Pruf, an anti-desiccant, and spraying the trees to cut down on mid-day moisture loss. What you are seeing is normal with transplants. Unless you get some blistering hot, windy weather, they should make it. If that should happen, syringe (spray) the foliage during the hottest parts of the day.

Q: My lilac bushes aren't flowering. I have about five of them about 4feet tall, and about the middle of last summer, I pruned. Did I cause the "non-flowering" by pruning too late in the season? Will they never flower again if I pruned off the buds? I don’t remember seeing any buds. I've lived here for three years now and don’t ever remember seeing the bushes flower. Any thoughts? (E-mail reference, Massachusetts)

A: Never-flowering-lilacs could be a problem. Typically, lilacs set their flower buds in late July or early August for the following spring's bloom. If they have never flowered it could be they are in too much shade or getting too much nitrogen fertilization for flower bud setting. Try to root prune them with a sharp-edged spade in a couple of places. Such trauma will often initiate the setting of flower buds for show the following year.

Q: I see in your column that Poast is registered for quackgrass in strawberries. Will it also kill dandelions and other weeds without hurting the strawberries? (E-mail reference)

A: No, Poast or Vantage is a grass herbicide only. Broadleaf weeds are another problem altogether.

Q: I planted two silver maples seven years ago and they have grown extensively. This spring I was surprised to find one leafed out first and the other much further behind. In addition, the top 4 feet of the tree died as well as one other branch. Have you any idea what may have caused this and what is the prognosis? (Grenville, S.D.)

A: The problem is likely a canker disease that has girdled the branch that appears dead. It could also be borers, but the likelihood of it being a canker is greater. Only a diagnosis can tell for sure. When something like this occurs, it is difficult to turn it around and still have a decent looking tree. I suggest getting an arborist out there ASAP for an accurate diagnosis and assessment.

Q: I know that you have to wait until lilac is done blooming to prune, but is there a time after that when it should be done? In other words, do you want to prune before some late date to protect next year’s buds and flowers? (Cando, N.D.)

A: The sooner after flowering lilacs are pruned the better. If pruned just as they are finished flowering, then energy will not be wasted making seed, and can go instead into new growth and making next year's flower buds.

Q: We have two large flowering crabapple trees that canopy our back yard. They are very beautiful with vibrant pink blossoms. Each year they seem to get very large cocoons of caterpillars on the ends on the branches. What are they? and how can we get rid of them? Are they destroying our trees? (E-mail reference)

A: Those are tent caterpillars, and they love fruit trees! While they are unsightly and can be locally destructive, they seldom cause sufficient damage to be worried about. If you can, cut off the ends of the branches they are on and burn them. Next spring, spray the tree with dormant oil while it is still dormant, and the oil will kill the overwintering eggs.

Q: A friend offered to dig up some nice lilac suckers for me to transplant in my yard. When is the best time of year to do this? Should we wait until after the bush is finished flowering, do it now while it's in full flower, or wait till next spring before it's flowered? (E-mail reference)

A: Waiting until this fall when it has dropped leaves, or next spring before it leafs out, are the better options for success.

Q: I bought a new house last fall and the subcontractors who laid the sod put it right next to the foundation on the north side of my house. I don't really like having grass growing right up to the side of my house, so I just removed the sod this last weekend. I happened to mention this to a few of my co-workers and they were adamant that I should have left it there as planting bushes, shrubs and flowers next to your foundation will cause the foundation to crack and cause all sorts of problems, and that the best thing you can do is to have sod growing up against your house. Is this true? I always thought it was our soil and climate extremes that caused foundations to crack.

I had planned on planting some hostas, begonias, astilbes, Impatiens and maybe a few other shade loving perennials. How far from the foundation should things like this be planted, if at all? (Fargo, N.D.)

A: It is interesting how slow bad advice is to die. Without insulting your coworkers, ignore what they said and plant your flowers and shrubs. The only rule is to plant them far enough away from the foundation so that they can get the rainfall. Often the overhang on the house will create a "rain shadow" where very little rain will reach, and the plants die. The only instances I have known where roots grow into the foundation is when it was already cracked and moisture seeping in, so naturally the roots followed--and they have received universal blame ever since!

Q: My wife’s small garden has had a trumpeter vine coming up in several spots for several years. We cannot find the origination of the vine (junk tree area near the edge of the garden). I would like to know if there is a weed killer that I could apply to one of the vines that would travel back and kill the vine at its roots. (E-mail reference, Michigan)

A: Yes, you can try "painting" Roundup on the leaves as they emerge. It will take some time and repeat applications, but it should eventually do the job. If you find the origin of the root system, you can also drench the soil with a solution of dicamba (make sure there are no other tree roots in the area) and that will get rid of the vine.

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.

###

Source: Ron Smith, (701) 231-8161, ronsmith@ndsuext.nodak.edu
Editor: Gary Moran, (701) 231-7865, gmoran@ndsuext.nodak.edu