May 15, 2003

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: Is there anything I can do to increase the survival chances of a single Colorado blue spruce planting? What should I do as far as soil prep, watering and fertilizer? (Amidon, N.D.)

A: Do not plant another Colorado blue. Instead, plant a Black Hills spruce. When digging the hole, make it wider than deep. Also, make sure the top of the root ball is covered with about 1-2 inches of soil and then create a "saucer" around the tree to collect water when it rains. Add about 3 inches of bark mulch and make sure it is well-hydrated before winter. Do not fertilize because it isn’t needed at this point. In October before freeze-up, spray the tree with Wilt-Pruf, and again in late winter or early spring during a thaw period. If this one dies, I'd suggest going for something else. Has the soil been tested?

Q: An individual came into the office with a forestry question that I thought you might be able to answer. Last fall he cut up a bunch of American elm trees for firewood. He heard from someone that in order to stop the spread of disease he should strip the bark off of any leftover logs that he would not be burning. This would evidently kill any beetle eggs that might be under the bark. He was wondering if this was true and if he should do this. (McClusky, N.D.)

A: Absolutely and it should be done ASAP. Ideally it should have been done before April 1.

Q: The crew that sided my house trampled my hydrangea. Any hope it will come back? It is a very large leaf variety with pale green blooms and, I think, quite old. (E-mail reference)

A: Thoughtless guys! But I’m willing to bet that you will get a regrowth this spring and in a couple of years the damage will only be a memory!

Q: How do you kill creeping bellflower in an established lawn? (Mandan, N.D.)

A: It’s difficult so you need to call out the big guns of herbicides. You need a 3-way product that contains 2,4-D, MCPP and Dicamba. There are several companies out there that sell this formula or one similar to it. A common one is Trimec which is usually available on the market.

Q: About five years ago my flowering crab broke off at the base of the soil (wind I guess). It started to grow again and is now about 8 feet tall but has never bloomed since. What do I need to do to get it to bloom again? It was about three years old before if broke off and used to bloom beautifully. (E-mail reference)

A: The tree was apparently grafted or budded onto a different species for rootstock but now the day length or other environmental conditions are not conducive to it blooming.

Q: My asparagus has already emerged but I was told that I could still use princep on it. After reading your information, I'm thinking that perhaps I shouldn’t. I have purchased the princep but have not applied it. Can I use it or is there something else that you would recommend? (E-mail reference)

A: Once the asparagus spears have emerged, no herbicide is recommended. Herbicide applications should be made in early spring. If your weed population is too high, it may be necessary to dig and reset the crowns in a more weed-free environment. Some herbicides I found in my references for use on asparagus are 2,4-D, Dicamba, Glyphosphate, Linuron, Paraquat, Sethoxydim, Simazine, Terbacil, and Trifluralin.

Q: My cottonwood tree shed some small brown capsules in mid-April. Many of them landed on my car and stayed there. They were coated in some sort of sticky stuff. When I removed them from the car, some of the sticky stuff stayed on the paint. I haven't found anything that will remove it. Do you have any ideas? Right now, I'm just a bit upset with that big, old tree. (E-mail reference)

A: A good multipurpose wax should do the job along with a good buffing. The seed capsules are bound to be sticky and the sap will leave a light etching on the car's paint but it can usually be buffed out. Contact your local car dealer to see if they have anything that can help you get rid of the marks.

Q: Are the purple cone like structures coming out of the ends of my Black Hills spruce actually new cones? I've always had blue spruce but I’m not familiar with Black Hills spruce. These trees are relatively young and have not produced a lot of cones. (E-mail reference)

A: Most likely they are the male cones. The female cones will follow a little later while the pollen is being disbursed.

Q: Can you recommend a variety of lavender hardy enough to survive our winters? (E-mail reference)

A: About the only one that comes close is the munstead cultivar of L. angustifolia. It all depends on where you live in N.D., the microclimate exposure, and the degree of protection you are willing to give it during winter.

Q: When should we put Weed and Feed on our lawn? Some of our neighbors fertilized in April but we were told once by a county agent that a good rule of the thumb is to do it about Memorial Day, Fourth of July and Labor Day. (Grand Forks, N.D.)

A: Your county agent was right but you should forget the Weed and Feed combo. If you have a weed problem, purchase a herbicide separately to get a more effective and easier control. Then fertilize your lawn -- sometime within the next week or two.

Q: I have a row of 30 emerald green arborvitae. They are planted along my property line about five feet from the edge of a paved parking lot. The tips on several of the trees are beginning to sag and look wilted. The trees look like they are being bent over from the weight of heavy snow weight but without the snow. Some of the tips of the needles have browned but that might be from a winter kill. There is new growth evident at the tips on top. Could my problem be salt damage or a fungus? (E-mail reference)

A: Thanks for the good description. From what you describe, it appears you have a high soil salt problem. To confirm, take a sandwich-bag sample of soil from the base of the plantings and send it to the Land Grant university in your state asking for a salt level test. I'm willing to bet it will come back very high in soluble salts. About the only thing you can do is try and leach the salts out with high quality water. Try to do that a couple of times a week for a month.

Q: I have a cotoneaster hedge which has to removed due to oyster scale. Apparently in the area of the community where I live it is a common hedge disease. I need to know how the roots grow. Are they down deep and spreading or shallow and spreading? When I planted them 15 years ago, the trench I dug was probably eight inches deep. Would you please let me know so we can remove them without doing too much damage to the existing lawn and flower beds. (Thunder Bay, Ontario, Canada)

A: Don't worry too much about where the roots are. Have a landscaper come in and rip the plants out, or better yet, have them cut back to ground level with a chain saw. After that have the contractor take a stump grinder -- there will be stumps after 15 years of growing -- and simply grind out the thick stump crown and adjacent thick roots. Any suckers that come up from extended roots can be easily controlled with a herbicide spray.

Q: I received a very old, root-bound hoya and repotted it in a terra cotta pot. It is quite long and hanging along curtain rods in an east-facing room. It seems healthy and loses few leaves. I fertilizer it about every three weeks. It has developed a few bunches of blooms but they fall off before they open. Could I be watering too much? (E-mail reference)

A: You are likely watering either too much or too inconsistently. Water enough to soak the entire root mass, then allow the upper one third to one half to dry before watering again. Also, since it is an old, pot-bound plant, it might need topdressing with potting soil as well. Try these two adjustments and see if that improves things.

Q: I have had a white crepe myrtle tree five feet or so from the end of our house for approximately 14 years. Last year I cut it down because I noticed we were getting roots growing toward our house. Even though I cut it down, the thing will not die. This year the roots are worse. We hear creeking during the day, probably at others times also. I’m afraid the tree is doing damage to our foundation. I’m almost sure it’s damaging our concrete slab. Please suggest something I can use to kill the roots. I have tried to dig it out but the roots are everywhere. I believe I will have to dig more out and replace all of the dirt (about a dump truck load) because the dirt has small roots in it that can reproduce. Can you suggest something chemical I can use? I will try almost anything. (E-mail reference)

A: I find it hard to believe that crepe myrtle can be a threat to the foundation of your house but it is too late to be concerned with that now. The best thing you can do to kill the roots is to spray the shoots that come up with a broadleaf herbicide. In other words, treat it like an unwanted broadleaf weed and don't bother digging everything up. The roots that remain will eventually rot and become an organic source of nutrients for your lawn and other landscape plants.

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