July 10, 2003

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: I have a yard full of mushrooms and don't know how to get rid of them. We’ve had a few on our boulevard where we had some trees but now they’re growing in our front and backyard. Any suggestions? (Fargo, N.D.)

A: Just ignore them. With all the recent rain, mushrooms have been sprouting up everywhere. When we settle into summer heat and extended periods without rain, they will disappear. There is no material available that will remove them.

Q: We have a white flowering crab apple tree. We pruned it last fall and this summer it did not flower. Did we do something wrong? Was it pruned wrong? What is the proper way to prune this tree? When is the best time to prune it? (E-mail reference)

A: You could have pruned off too much. You didn't say whether or not it leafed out, but I assume it did. The best time to prune is early spring before new growth emerges, depending on where you live.

Q: Is it okay to mulch hollyhocks or will the mulch increase the chance of disease? (E-mail reference)

A: The risk of increased disease is so minuscule that it isn't worth worrying about compared to the advantages of mulching.

Q: I would like to try to grow some spruce trees from seed. What provides the seed, the male cone or the female growth? When should I harvest the seed? (Gann Valley S.D.)

A: Find some female cones that are still closed at the terminal ends of the lower branches (the male cones would no longer exist as they would have shed their pollen) and tie a small brown paper bag around a few until mid-September. Open one to see if the seeds have been shed. Plant the seeds where you want them to grow. They do not need to go through any cold pretreatment. The normal practice is to sow them into cold ground and wait for what next spring brings forth! If the cone has not opened, reseal the bag and wait a few more weeks. If the cone has opened and there are no seeds, then the pollen missed the mark which would be unusual or you covered them too soon.

Q: For the last two years our peas and string beans have failed to come up. We have very sandy soil. Over the years I have tilled in most of the leaves from the trees in our yard.plus the fall grass clippings. I apply 10-10-10 fertilizer each spring before the last tilling. What am I doing wrong? (Wadena Minn.)

A: My best guess is that you have some herbicide residue in the grass clippings that is acting as a pre-emergent herbicide. Some herbicides have good residual even when composted.

Q: There is a white powder on my grass that seems to be spreading. It started on the boulevard but has now spread to the back yard. It has to be some sort of mold. Can it do any damage to the quality of my yard? Is there a treatment for it? It seems to sit on the blades of the grass and is not causing any real harm but I don't want it to turn into something major. (Fargo, N.D.)

A: This is powdery mildew that usually shows up on Kentucky bluegrass that has been seeded within the last year. It usually shows up on grass that is in shade part of the day and is getting normal fertilization and watering. It is non-lethal to grass. Powdery mildew can be controlled by using good management practices such as mowing at the optimal height of two and a half to three inches, mowing frequently (using not more than a third of the blade at each mowing), and mowing when the grass is not wet. Unless this is a particularly susceptible cultivar to this fungus, as the grass matures, it will develop resistance to this benign fungus. If this turns out to be a recurring problem, then the problem is, most likely, too much shade for the cultivar being grown. You then have the option of either re-establishing a turfgrass system with resistant species or cultivars that can thrive under those particular conditions or opening the tree canopies to allow for greater sunlight penetration.

Q: I have a split leaf stag horn sumac. The top is not growing but the middle and low part of the bush is taking off like crazy. Is there something I should do to it in the fall or spring? (Fargo N.D.)

A: Cut out the dead material and allow the emerging growth to take off. This often happens with sumac in our area. During the winter there is a die-back of the aerial part of the plant, with the rhizome surviving and sending up new growth.

Q: I have a question about our jade plant. My husband repotted it into a bigger pot a couple of months ago. It was doing really well but now he noticed that there are some white spots on the leaves. Do you know what we can do to take care of the white spots? (Fargo, N.D.)

A: It is probably powdery mildew showing up with the high humidity and favorable temperatures we have been experiencing. Try wiping it off with a cloth soaked in light vegetable oil.

Q: I have some green ash trees that are about 10 years old. The last couple of years I’ve noticed that the bark seems fragile and has been breaking or peeling off. It’s nothing major but it does have me concerned. I wrapped them last year and then took the wrap off over the winter. I have them wrapped again now and I painted any wounds or cuts with pruning spray. The leaves were fine except I did notice one was curled. Any ideas or suggestions? (Stanley, N.D.)

A: Leave the tree alone unless you want to wrap it going into the winter. However, ash trees usually don't need such attention. In 99.9 percent of the cases, green ash trees need little care after planting. In spite of what they go through, there is usually nothing terminally wrong with them unless you get too intrusive by painting wounds with pruning spray and wrapping. One leaf curling is nothing to worry about.

Q: I recently received a blue hydrangea for Mother’s day and would like to move it outside. The flowers are starting to die back. The blooms that are still on the plant are turning green. I drench it thoroughly when watering but let the excess run off. It is still in its original container. Where is the best place outdoors to plant it and what type of soil does it prefer? Can I leave it outside for winter? (Mazeppa, Minn.)

A: Move it to where it can get some sunlight but not direct all-day sun. Dappled shade is best. It will probably not survive the winter in Minnesota, so consider it a brief gift to be remembered or bring it inside for the winter. The flowers turning green is natural and nothing to worry about. Remove the flowers when they turn brown.

Q: We are moving to a new house this fall in West Fargo. I have several red twig dogwoods in my yard that I would like to take seed from and plant in our new yard this fall or next spring. In making a hedge, can I put down weed fabric protector and then rocks around them? Should I just buy new bushes next spring? (West Fargo, N.D.)

A: The easiest and least frustrating approach is to purchase some new shrubs next spring. The results will be quicker and you will be happier.

Q: Could you please tell me the average amount of water that a large cottonwood tree uses per day? The trees are near a river and irrigation ditches. (E-mail reference)

A: It can vary all over the place. If they are growing in an arid climate, it will be higher due to the transpiration pull being greater than in a more humid region. It also depends on the wind speeds the tree encounters along with other vegetation in the tree's region. Someone apparently calculated that the "average mature deciduous tree can consume over 200 gallons of water per day in the peak of the summer." I have no idea where that summer was but at least it’s a starting point for you.

Q: So many recipes lately call for cilantro so I bought some plants this spring. They are growing like mad. They are getting very tall and look like they may blossom and go to seed. Can I cut them off and will the plant bush out? (Aberdeen, S.D.)

A: By all means dead-head them. You will have cilantro growing forever if they go to seed..

Q: We have a row of Lombardy poplars. Our former vengeful neighbors planted another row of poplars parallel to ours on their property. The new poplars did not do well so the new neighbors pulled them out. Now suckers and roots are growing from the pulled out trees. The new neighbors claim the suckers and roots are coming from our trees. What do you think? (E-mail reference)

A: You both have self-inflicted headaches. The Lombardy poplar ranks among the worst trees to grow for landscape purposes. The root suckers are coming from both of the plantings and will continue to do so for years to come. You would be better off pulling yours out and both of you getting the stumps and roots ground out and then smoking a peace-pipe. There are much nicer trees that can define a property line in a non-offensive manner.

Q: I have an autumn blaze maple that I planted with a tree spade three years ago. This year the leaves are progressively getting more and more yellow while the arteries within the leaves remain green. The nursery instructed me to fertilize with iron which I have applied on two occasions this year. I also applied yellow leaf sickness capsules using a root feeder. The last application was Friday, the first approximately five weeks ago. It seems as though the tree is reacting slowly to the treatment. Is there any hope for this beautiful tree? Can I do anything else? Should I continue with more treatments this year? If that doesn’t work, what shade tree do you suggest that is hardy, grows fast and will add beauty to my front yard? Hopefully your input will give me some hope that the tree will survive! (E-mail reference)

A: Tree spade operators will not like my response. You would be better off planting a younger tree that has all the roots intact. It will grow faster, have fewer problems and will be a heck of a lot cheaper. I have found anecdotally that trees of the same species that are planted with all their roots intact from a container, such as a 10 gallon pot, will attain the size of the spaded tree in a few years and be healthier at that point. Typically, in spaded trees, anywhere from one third to one half of the root system is left in the soil which is mostly the part of the root system that is responsible for nutrient and water uptake. They arrive at the new site looking great above ground but when it comes to being able to absorb the soil nutrients, many are unable to do so, and crown die-back becomes evident over the next few years. That being said, I have to also say in defense of some spade tree nurseries, they realize this problem exists and follow a practice of regular in-site root pruning to develop a complete root system within the tree spade ball. Those trees then have an excellent chance of growing. Your autumn blaze maple is a good selection. I encourage you to stick with it.

Q: Is it hard to grow little oak trees in this part of the state? My brother planted two little ones a couple of weeks ago that turned yellow and died. He got them from a guy in Grassy Butte where they were growing wild. He has been watering them and he used bark to put around them. Any ideas as to why they died? (E-mail reference)

A: Oak trees do not transplant well because of their tap root system. He is better off getting seed (acorns) and planting them where he wants the trees to grow.

Q: Some of the choke cherries I planted from bare stock last year were growing well but now have dark red leaves and look sick. What do you recommend if this is something serious and I have to replace them? I was planting them for the berries. (Sheyenne N.D.)

A: There are other berry-bearing trees that you should consider because the choke cherry has gained a reputation for suckering profusely and being vulnerable to black knot fungal disease in our area. Juneberries grow beautifully and are not plagued with as many problems.

Q: We live north of Bismarck on a couple of acres of clay soil. In the summer of 2001 we purchased three ash trees that were discounted because of moderate hail damage -- two patmore ash and one fallgold ash. We planted the patmores on the north side of the lot and the fallgold on the south side. I know we took a risk in planting hail-damaged trees but we couldn't pass up a bargain. They seemed to do pretty well that first summer and last summer, despite the dry weather. This year the patmores have little to no leaves on the west side. All the foliage is on the east side of the trees. The branches on the west side are still pliable so they aren't dead. There is also a distinct difference in the color of the bark. The east side is grayish while the west is brown. We did have a strong freeze this spring after the trees started budding but I can't imagine that it would have affected only the west side. Is this just an indication that the trees are not long for this world? Is there a chance they can come back? For what it’s worth, the leaves on the east side look healthy. The fallgold, which is slightly more protected from our incredibly strong northwest winds, is doing fine. (Bismarck, N.D.)

A: The trees may live but will they be an asset to your property? I would suggest replanting the two and keeping the fallgold which you indicate is doing . The true long-term damage from hail will not show up until a few years after the event. You took a chance and got one bargain out of three so consider yourself lucky!

Q: Two thirds of my daffodils only came up half way or less and produced no flowers. This happened last spring too. The soil is not hard and I fertilize regularly. Are they too deep? I followed the package instructions for planting. Also, for how many years should a person water transplanted trees? They are ponderosa, spruce, and ash trees. (Onida, S.D.)

A: The daffodils are planted too deeply or they are in too much shade such as the north side of a house. If things don't improve next season, dig them up and replant but not as deep or replant in a sunnier location. The first season is very critical. Regarding your transplanted trees, I generally recommend three years of watering unless in a drought situation. By then the root system should be well enough developed to mine adequate moisture out of the soil between normal rainfall events.

Q: This spring I planted a row of seven poplar trees, a row of 35 Lilacs, a row of 15 sumac and a grouping of three red maples. All of the plants came from our county Soil Conservation Service. I've made about 20-24 inch diameter rings to hold mulch out of thick plastic edging for each tree or bush. They all seem to be doing very well. I’m almost finished putting plastic and rock on top of each row to prevent any grass or weed growth in between the trees. I mulched heavily inside each ring with cypress mulch and water thoroughly once a week if we don't get rain. The trees and the landscaping all look great but are there any problems that the plastic and rock could cause? Is there anything else I should do to keep them healthy? (Lisbon, N.D.)

A: It sounds to me like you’ve given the project a lot of thought and done a lot of work to get these plants established. If you haven't overdone the mulch around the plants (greater than four inches), they should be ok. It certainly will not be your fault if they don't turn out beautifully!

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: Rich Mattern, (701) 231-6136, richard.mattern@ndsu.nodak.edu