July 26, 2001

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: I am finding our new grass as well as new grass in other places is turning brown. I am wondering if this isn't caused by the heat. If it is, do I need to replant or will this come out of it when it cools down? (Lisbon, N.D.)

A: Most likely it is the heat. Try to maintain a consistent moisture level by watering every other day during heat stress. As to whether or not it will recover, only time will tell. Kentucky blue is fairly tough stuff and has the ability to bounce back from hot spells. A lot depends on the maturity of the crown of the plants and whether or not they dehydrated completely to the point of death and not just dormancy.

Q: I read somewhere years ago that spider plants and ferns were good for combating indoor air pollution. I have not seen anything sense and am curious as to whether this is true. (E-mail reference, Washington, D.C.)

A: Absolutely! It takes more than tokenism though. The interior of a home should be generously "landscaped" with such plants. Any live plant is better than none; the more the better. The study was conducted by the USDA a dozen or so years ago.

Q: In May 2000 I planted a ‘Cathedral’ elm. Its leaves this year are pale yellow-green. I fertilized this June, but the leaves have only darkened slightly. Now within the last week they have developed light yellow to almost white spots on virtually all the leaves. Should I fertilize again? Also, can you recommend a reliable purple-leafed plum that produces sweet fruit and doesn’t get over 20 feet tall or so? I’d like to use it as an ornamental in our front yard; it would be on the northeast side of the house. (Fargo, N.D.)

A: I do not recommend fertilizing again this year. I would like a leaf sample so our Plant Diagnostic Lab can evaluate it for a disease problem. The ‘Newport’ is an attractive ornamental plum that tops out at 20 feet in southern Minnesota. It should stay under that in North Dakota. Purple leaf sandcherry has purple foliage, bears purplish fruit in August and gets to about 8 feet tall. In my opinion the ‘Princess Kay’ is the most beautiful plum around. The flowers are double and very fragrant.

Q: The tag on a tree we bought says it’s an Emerald Green Maple, yet the picture on the tag does not look like this kind of leaf on the tree. What do you think? Is this a good choice for our area? (Jamestown, N.D.)

A: I identified your leaf before I saw the tag, and yes, you have the right tree. The Emerald Lustre® or ‘Pond’ is a cultivar of the Norway maple, one of Bailey Nursery’s finest selections for vigorous growth and good form. Don’t fertilize after Aug. 1 and don’t keep it too moist going into the fall, so it will harden off adequately going into winter. You’ve picked a good tree and I wish you success with it.

Q: I have three new Norway spruce trees. I have noticed several shoots that have been "deneedled." I saw one wormlike critter, which I removed. Also, on a lower branch, is a black substance that looks like motor oil. I suspect that the "worm" has eaten the needles, but I doubt that there was only one. How can I care for the trees? Is the oil slick related to the worm? (E-mail reference)

A: It sounds like spruce sawfly larvae are the problem; they can be controlled with a spray of Sevin insecticide, or simply pick off the larvae as you see them. The other sounds like a canker of some kind. I would suggest contacting a forester or horticulturist locally for a visual diagnosis, or send a sample into the plant diagnostic lab at your state university for positive ID.

Q: We live in Wisconsin and in a recent windstorm lost our lovely 100-year-old maple. The loss of this tree is quite sad, as it completely shaded our back yard. It stood about 70 feet tall. The tree service recommended that we remove the tree as a large branch had fallen on the house and damaged quite a large section of our roof. As part of the tree removal service, they ground out the stump. They said we may not be able to replant a tree there because of the roots. My question is whether or not we could plant another maple on the same site. Could you recommend a fast growing type of maple that you think might work out? We miss our tree! (E-mail reference, Wisconsin)

A: Yes, you can plant another tree there, but I wouldn't suggest the silver maple which is the fastest growing of the maple family. Being softwooded, and tending to develop narrow crotch angles which break easily in windstorms, I'm afraid I would be recommending something that is more a liability than an asset. This is a generalization for all fast growing trees. They tend to break up in windstorms or under heavy snow loads easier than the slower growing ones. Sugar and Norway maples would be better choices, and once established past the first year or so will put on decent growth. Other choices might be white or green ash, American linden, a whole family of oaks, hickory, hackberry or one of the DED resistant elms. Whatever you plant, make sure that fresh soil is in the planting hole, and not just the sawdust from the stump and roots. This can be soil from another place on your property, not anything you have to purchase or haul in.

Q: About six years ago I bought two ash trees that were listed as a "North Dakota Hybrid". Two years later I could not find that tree at any place that sold trees I was told that the North Dakota Hybrid may also be called "Dakota Hybrid" At one place I was told that tree was a poor choice and that the "Patmore" ash was a better tree. The two N.D. Hybrids are the best trees I have. They are well shaped and least 25 feet tall. The Patmore ash has grown only a few inches in the past three years. My question is, where can I find the N.D. hybrid ash trees? (Faulkton, S.D.)

A: My goodness, how we try to sell what we have and downgrade what we don't carry! The so-called North Dakota hybrids are several cultivars developed by NDSU's Dr. Dale Herman, and I assure you they are anything but inferior to any other ash tree on the market. He has the patience of Job in evaluating his trials before releasing any selections to the market. His introductions include Dakota Centennial ash, Prairie Spire ash, and Prairie Dome ash. All three were introduced in 1988. As to where you can purchase them, I'd suggest giving Bailey Nursery in the Twin Cities a call and asking them where the trees are being retailed. I know they are being sold at most of the nurseries in North Dakota and Western Minnesota.

Q: We planted 6 to 7-foot ash trees about six weeks ago. About 10 days ago the leaves started browning and curling and falling off.I have read about anthracnose diseases, but there is also bright orange color along the trunk of the tree. Any ideas? (Gettysburg, S.D.)

A: It sounds like a case of ash rust hitting your tree, along with the possibility of anthracnose. At this stage, there is little you can do about either one. Rake up all fallen leaves for now, and next spring spray the trees with lime-sulfur while still dormant, but when the buds are starting to swell. At the green tip stage of the buds, spray again, this time with a chlorothalonil product such as Daconil 2787, and again with the same product when the leaves are fully grown.

Q: You mentioned spraying with Bt for potato bugs. You also said it would not leave any residue on the tubers. Does dusting the potato plants with Sevin leave residue on the tubers? Is it absorbed through the leaves? (Bowdon, N.D.)

A: Neither the Bt (aka Dipel) nor Sevin leave any residue on the tubers.

Q: I have apple trees that are having deformed apples and some of them are dropping off. Some of the apples don't even grow any bigger then a grape. What could the problem be? They are Haroldson apple trees, about 7 years old, and we have always had good apples before. I can't see any bugs or leaf damage to the tree or apples. (Buchanan, N.D.)

A: Spring or early summer apple drop is normal where the fruit set is heavy. Nothing to worry about. It’s Mother Nature's way of population control!

Q: Last year I planted seven pyramidal arborvitae trees. The landscaping company said to wait a year before mulching. Recently my neighbor had some extra mulch, so I took it. The mulch is that shredded type. Two days ago I watered the trees after mulching for about 90 minutes. Today I checked the mulch to see how damp it is. On the bottom (about 2 inches thick) the mulch was only a little damp so I watered the trees again for about 30 minutes. Did I use the right type of mulch? How often do I water the trees? (E-mail reference, Green Bay, Wisc.)

A: The only mistake you made was in the order of operations. First of all, I have no idea why your landscape company told you to wait a year before adding mulch. I had my own business, plus I worked for four other contracting companies, and our policy was to always mulch upon completion of the plantings, with no negative effects. But first, we watered down every planting before applying the mulch. What you are experiencing now is the mulch's ability to shed water. I suggest pulling the mulch away from each plant, laying a soaker hose along the whole row and allowing it to run for an hour or so, then covering it with your shredded mulch, no more than 3 inches thick.

Q: We moved into a house with beautiful lilacs all the way around the yard. On one side they are nicely kept and trimmed into a beautiful hedge. On the other side they are about 10 feet tall or taller and there is no fence, only the lilacs. We want to put a fence in but have to cut down the lilacs. How short can we cut them and still have them come back after we have our fence in? I don't want to kill them , but I have small children and we must have a fence so they are safe to play in the back yard. (Ames, Iowa)

A: Lilacs are pretty tough customers and can survive just about anything short of a land mine explosion. If you have to install the fence this summer, wait as long as possible to cut the lilacs right back to the soil line. This is to allow as much time as possible for the plants to build a carbohydrate reserve for next season's growth spurt. If this is something that you are planning on doing this fall or next year, then cut them back when they have gone dormant. The resulting growth next year will not produce flowers, but it will the following year.

Q: I am growing cucumbers for the first time, and they are getting large, but they are also turning yellowish in color instead of green. Can you tell me why? (E-mail reference)

A: Yellow cucumbers could be the result of planting a yellow fleshed cultivar. Otherwise it could be a virus, too much water or nutrient imbalance. I would suggest picking those that are turning yellow to encourage more fruit set to see if they emerge green.

Q: We are having trouble establishing a new lawn. Pigeon grass is coming up everywhere in the soil including flower beds and the garden. Is there a spray to use in the lawn once it has been mowed several times, or if nothing is done this year, will it be in the lawn next spring? Is there anything that can be used in the garden or flower beds besides constantly hoeing? (Aberdeen, S.D.)

A: Your best bet is to live with the foxtail for now and use a herbicide containing pendimethalin early next spring before new growth begins. I am afraid that anything you would apply right now would hurt the new grass seedlings and inhibit further germination of the desired seed. For the flower bed, you can use a product known as Preen. Clean cultivate first, then apply.

Q: We planted a Linden (Greenspire, I believe) two years ago. It appears to be struggling. It’s about 12 feet tall. The outer branches have clumps of growth with green heart-shaped leaves and yellowish fragrant flowering. Nearly all of the green leaves have a slight curling, but are not completely curled or damaged. However, clumps of leaf/flowering are sporadic along the outer branches. At some points there are 1-foot stretches of bare branch between growth clumps. There is growth on the tips of all outer branches. We planted the tree in a lawn area that is watered three or four times per week for 45 minutes during the hot summer season. The lawn area is ever so slightly sloped to the tree. Did we plant this tree too deep? Or could we possibly being drowning the tree with too much watering? (E-mail reference, Erie, Col.)

A: Trees--lindens especially--and lawn sprinkler systems are usually not meant for each other. In the situation that you described, I would say it is being drowned from too much water. I also advise you to replace the tree. It might live, but it will likely not be a property asset. Lindens are beautiful trees--one of nature's finest and most beautiful--and can be a real asset to your property. Replanting (or having it done for you) with another will reward you down the road with a tree that will increase the value of your property. Also, I would suggest you get an irrigation contractor in to have them adjust your sprinkler system so the water stream is not impacting the tree. It can be done for little cost, and it will be worth it!

Q: My strawberries are getting mushy and decaying on the plant. Any ideas on the cause. (Jamestown, N.D.)

A: Didn't pick them soon enough! Check the patch daily and pick those that are just ripe, not two days later or they will turn to mush. It could also be that they have been kept too wet.

Q: I am having problems with what appears to be blossom end rot in zucchini. Can that be the case, and what can I do to prevent it? (Fort Yates, N.D.)

A: Blossom end rot is possible in all vegetable production, and the cause is the same whether it is on tomatoes, peppers, or squash: irregular watering (or rainfall) cycles, root damage, too fast a rate of growth for the calcium to reach the end of the fruit when the cells are forming.

Q: I saw some information about this buffalo grass (Bucheloe dactyloides "Legacy") in one of the garden catalogs, and since I would like to get more and more into xeriscape landscaping this type of grass looks promising. Beside greening up later in spring and not doing well in shade, are there other draw backs? (Moorhead, Minn.)

A: Buffalo grass is definitely xeric; however, in addition to greening up late, it also goes dormant with extended drought, and usually with the first frost of fall. Also, the seed is expensive and poor at germinating. Plugs are the only practical way to go, but they too are expensive and require hand weeding between the plugs until the grass covers the area. Once established, it makes a fairly attractive grass--not a rich green, but a grayish green--and requires little input as far as water and nutrients go. A better grass for your area is tall fescue. Get either Bonanza or Rebel, Rebel Jr., or Rebel II. Do not plant Ky 31 tall fescue. That is a roadside grass. I have had Bonanza in my backyard for the past 14 years and I am pleased with the performance it has provided. It grows vigorously, requires one fertilization a year, and I water it about two or three times a year, more out of guilt than necessity. For every four to five times I irrigate my front lawn of Touchdown Kentucky bluegrass, I water the Bonanza once. Just make sure you sow the seed on the dense side--about 5 pounds per 1000 square feet--and you will have a lush, dark green lawn that will do well in both sun and shade. Mow it high, at 3 inches, and I'd be surprised if you didn't end up loving it!

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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