July 5, 2001

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: We have a large weeping willow tree that is about 9 years old. This spring it got nice leaves. Now lots of the little weeping branches have lost their leaves. We have had some very strong gusty winds, but that has not bothered it before. Is there an insect that loves to eat on the pretty weeping willows? (Platte, S.D.)

A: Unfortunately, there are a host of insects and diseases that "love" the weeping willow! My suspicion is that it is one of the many canker diseases that afflict this species. If it were insects their presence would be fairly obvious.

Q: I have a rhubarb sample that has leaf spotting on it. Is that typical of rhubarb? One stem has what I'd call worm feeding, which appears to have penetrated the outer layer. Then that area has turned brown like an exposed apple. Surrounding the brown is purplish area. ( Ellendale, N.D.)

A: It sounds like a leaf-spot fungus. If you have only one or two leaves affected, then simple removal of those leaves will suffice. If it appears to be spreading, then a spray with Captan is recommended, but the crop cannot be eaten for the balance of the season after that.

Generally this disease is mostly localized and not lethal to the plant.

Q: This is a comment to the person who wanted to pot up a peony to move it. I did this three summers ago. I took a small root from the outside of the plant, and put it in a 2-gallon pot. I had this peony in its pot until this spring. I wintered it with bags of leaves stacked around it. I set it in its permanent place this spring, and it had several flowers on it. ( Driscoll, N.D.)

A: Thanks for the tip. I'm sure all who want to move their peonies will benefit from the information you provided--nothing like real-life experiences to prove something right!

Q: I need some help with a Canadian Red cherry tree in my yard. I noticed black knot for the first time this winter. I removed all the knots in March. I removed about twice as many branches this week. They were fresh knots. The tree is about 5 years old, and if I should abandon ship, I would like to do it now and plant an apple tree in its place. If there is some hope of stopping this disease then I would like to try. (Ypsilanti, N.D.)

A: Abandon ship! You will be doing the environment a favor by removing another vector of this disfiguring disease. I suggest a Honeycrisp apple.

Q: I have a spot in my yard where I am looking to plant an ornamental tree. I have it narrowed down to either a Robinson crabapple tree or a birch. I know these are two entirely different trees, but both have things I like about them. I like the crabapple for the color of the leaves and small fruit, and the birch for the bark. I live on 3 acres and have an area coming up to the house where one of these would go. It is next to a brick walkway/flower bed. (Glyndon, Minn.)

A: You are better off with the birch. The crabapple fruit would drop on the walk and cause some problems, plus they would attract birds that can be messy on sidewalks.

Q: We recently obtained a 5-inch potted jade plant (Crassula argentea). It appears healthy; in fact all five branches are sprouting a pair of new growths. If we remove these will we encourage the plant to become more bushy with "sprouts" in the lower areas as we wish ? (E-mail reference)

A: Yes. You want to perform what is known as "pinching," taking the thumb nail and forefinger and removing a portion of the new growth back to a leaf axis.

Q: We have a 30-year old lilac bush that stopped blooming about three years ago. What do you suggest...a drastic pruning, replacement or continued patience and more TLC? ( Brossard, Quebec, Canada)

A: Replacing a 30-year old lilac bush is no small chore. It will have a root and crown system as vast as the Mall of America! If it were me, I would try chain-sawing the thing down to see what happens first. That may bring it back into a blooming cycle.

Q: I have the enclosed sample growing in my yard. I use Roundup on it, but it only kills it for a while and then it comes back. (Bismarck, N.D.)

A: Small wonder. It is knotweed, which is very difficult to control at this stage of growth. You need to do two things: Correct the compaction which is allowing this weed to establish and flourish by core aeration. Use a herbicide known as TRIMEC. It usually does a better job than Roundup. If you succeed in killing it off this year, then re-seed around Labor Day weekend. Then next spring, apply a broadleaf pre-emergent herbicide that will control Knotweed seed germination. Do this before, April 1, as this seed germinates early.

Q: My neighbor has a cottonwood tree his yard that keeps sending shoots up in my yard. I have killed them in the past with Roundup. The tree blew down last summer and all that is left is the stump, but the shoots are coming into my yard faster now. Is there some way I can kill the roots and life that is still in the stump so that it quits producing shoots in my yard? (Devils Lake, N.D.)

A: Try TRIMEC. It is more potent and translocates to the roots. Wait on mowing one day after spraying to allow for maximum absorption.

Q: I started my tomatoes under grow lights in the basement. After the weather warmed up I moved them to the greenhouse. I have a disease infecting all six varieties of tomatoes. What is it? I sprayed it with Maneb. Enclosed is a sample for you to look at. Also, my spruce have something wrong with them. Can you please tell me what? (Regent, N.D.)

A: Your tomatoes are showing symptoms of phenoxy herbicide damage. It is either a contaminant in your soil or it has drifted in through your greenhouse ventilation system. The spruce samples you sent show symptoms of both needle cast and drought damage. Spray with Bravo (chlorothalonil) in June and July to control the needle cast. For the drought affected ones, water would solve the problem.

Q: We have peonies that have been planted for some time. Our problem is one of the plants had over a hundred buds last year but didn’t come up this year. Also, some of the plants have red leaves and seem to be getting smaller this year. We have fertilized with sheep manure (that has been aged) every fall but last year. What else can we do? (Gettysburg, S.D.)

A: Try digging and dividing--not now, but early fall after a couple of hard frosts. Be sure to not set the divided crowns any more than an inch below grade, or you’ll have a host of new problems.

Q: Just letting you know that I have a Reliance peach tree and an Orange quince tree that, with a lot of TLC, both survived the past winter. Early in the spring of 2000 I made two 6-foot-deep conical dugouts in a sandy hillside and lined them with rocks averaging about the size of a softball. The trees were planted in these dugouts, and last fall I covered the tops of the dugouts. Each dugout has about a 2-foot-diameter base and about a 5-foot-diameter top. This spring when I uncovered the dugout with the peach tree I was surprised to find a green leaf at the top of the tree. Within a few weeks after uncovering both trees were fully leafed out. This summer I hope to make a long, narrow, deep trench in which I'd like to eventually plant cold-sensitive plants such as jostaberry, blackberry, Suffolk Red grape, Mericrest nectarine, cold-hardy almond and several more. ( Warroad, Minn.)

A: My only comment is, "There are no more determined people on this earth than devoted gardeners!" For all the work you went to, you deserve some kind of medal, or at least to be able to harvest the fruits of your labors. Better guard that tree. Someone (like a fresh-peach starved neighbor!) might just pull a midnight raid.

Q: I was looking for a recipe for insect spray made from rhubarb leaves when I ran across your response to someone who maintained that they knew of a rhubarb patch that was 70 years old.

Your response was that it was impossible. You maintain that it should be moved every six to10 years. I have a patch on my property that is at least that old, never been moved, never been fertilized, never had manure added and it still produces two crops of rhubarb in a year. My only problem with this patch is keeping it from spreading into a surrounding flower bed. This is what is left of a 30-foot patch that has taken me years to reduce. The soil that it grows in is a good light loam. It produces sufficient stalks to supply my wife and her friends with enough for pies, muffins etc. as well as the 20 pounds of rhubarb stalks needed to make my yearly 23 liters of excellent rhubarb wine. (E-mail reference, Ontario, Canada)

A: Send me some of that wine! And, I'll never use the word "impossible" again when it comes to gardening wonders. I just came back from a cruise to Alaska and saw a rhubarb plant that was over 2 meters tall and at least as wide, growing in a little cut-out between sidewalk and wall, with no obvious fussing. Never second guess the powers of Mother nature!

Q: We bought a home that has a grape vine growing on the clothes line. The fruit is purple and sweet. The soil under the sod is an old gravel pit. Last year the fruit had a white mold or fungus growing on it. What do I treat with? How do I prune it? What should I fertilize with? ( Valley City, N.D.)

A: Pruning, the remedial kind anyway, is out for now. That should be done in the early spring when the vine is dormant. Spray the vine with Bordeaux mixture, which is obtainable at any garden supply store, and follow the directions on the label. Fertilize in the early spring while still dormant with 1 pound of 10-6-4 or something similar.

Q: About 10 years ago we planted four Potentilla bushes in the front of our house (south side). They bloomed beautifully for many years. In the last year or two they have been flowering less and less, and now three of them are completely dead and the last one has only a few blossoms on it. Over the years the cats would use them as scratching posts and weeds have grown around them quite a bit. Could we have done something to save them? (E-mail reference)

A: Regular pruning and weeding would have been a big help. If they are not completely dead, then perhaps it is not too late. Early next spring while they are still dormant, cut them back completely to the ground and put 1/2 cup of fertilizer around each one. If there is any life left, you will get a mass of new, fresh growth that may or may not bloom that same year. If not, it will almost for certain do so the following year, assuming that they are not now growing in shade.

Q: We know about harvesting asparagus only at the beginning of the season and then letting it grow to make food for the next year's crop, but I'm wondering about whether we should harvest all the spears, thick and thin, when we're harvesting, or should we just be harvesting the thicker ones? We didn't get around to seeding some Kentucky bluegrass in a sizeable area until late spring. What are the drawbacks for seeding this late? We have several apple trees that have set too much fruit. Other than hand picking some of it off, which isn't practical on our bigger trees, how can we thin out some of the fruit? (Actually, in this area, Mother Nature does a pretty good job of thinning, but sometimes even she needs some help!) ( Aberdeen, S.D.)

A: Harvest all the asparagus spears. From an edible standpoint, the thin ones will be just as tasty and nutritious; from a marketing one, only the thicker ones are used. No drawbacks to the grass seeding. In fact, everything is in your favor. Warmer soil equals faster germination, you are past the spring "flush" growth of weeds and hopefully the washout rains of earlier plantings. You may have to be a little more conscientious about water for the young seedlings should the hot weather of summer bear down too much. A couple of mistings during the mid-morning and afternoon of those days would be good to keep them from becoming heat stressed. There is nothing currently on the market that dependably helps thin apple fruit for the homeowner. You are right, though, June apple drop helps to naturally thin the crop for you. I would suggest trying to brace or support those branches that seem to bearing the heaviest load to prevent breaking during a windstorm.

Q: I just planted a birch clump in my front yard. The root ball of the tree was just wrapped in burlap. I noticed when it was planted that there was not much of a root system in the burlap. The tree just doesn't seem to be doing well. The leaves have not grown any larger. The only new thing new with the tree lately is that the catkins, which were very small and skinny, have now plumped up. I am hoping that this is a good sign, as there are a few branches that are completely dead. Also, can I safely cut off the dead branches or should I wait until fall? Could the tree be planted too deep? I have watered with transplant fertilizer every other week. (E-mail reference)

A: I hope the tree was dormant when you obtained it and planted it. Bare root birch trees are generally not a good choice. Better to obtain a container grown specimen. You can go ahead and prune out the dead branches at this time. You do not need to add fertilizer as often as you are doing. If the tree is going to survive, it will do so on the soil's nutrient content and water (which is more important to the tree now). Birch have a shallow, but spreading root system. I am afraid that the nursery may have cut off too much root for convenience in handling to do the tree any 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