NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665

May 20, 1999

Ron Smith, Extension Horticulturist
North Dakota State University

Q: Will Poast work in a rhubarb bed to get rid of grass? Also, when rhubarb sets its seed pod along with the stock in the spring, what needs to be done? (Fosston, Minn.)

A: Poast is a selective herbicide with a broad spectrum of post-emergent activity, especially suited for grassy weed control. In checking the extensive label, I find that Poast can be applied up to 15 days of harvest.

When the rhubarb sets the seed head, cut it out immediately so that photosynthetic energy is not wasted. We want it to all go into growing new stalks!

Q: For the past two years, I have had tiny spider mites (?) choke off my First Lady marigolds by spinning webs all over them—almost overnight. How can I prevent this now before planting, or should I change variety to Cracker Jack marigolds? (Finley, N.D., e-mail)

A: Your problem does not sound like spider mite activity. Spider mites typically do not bother marigolds. And the fact that you use the statement "choke off" by spinning webs almost overnight leads me to believe it may be something else. Spider mites are smaller than the dot at the end of this sentence, and their webs are very minute, almost going without notice, until the plant totally collapses. Finally, they are usually more of a pest on perennial plants that don't get the attention annual plants usually do.

That all being said, what, you are wondering, could be the problem? I believe it is likely Verticillium wilt, since you specify it attacking your First Lady cultivar. Verticillium wilt is a soil-borne fungus that attacks susceptible plants. The Crackerjack marigold may have the resistance bred into it.

I suggest extremely good sanitation this spring, cleaning out the beds before planting anything in them. Then, if you can give up your romance with marigolds and try, for instance, some of the new zinnias or salvias in that spot, practicing crop rotation may make a difference as far as disease buildup goes. If you simply cannot give up marigolds, then plant a different cultivar than First Lady.

Q: Enclosed is a leaf sample from an African Violet plant. I have lost several other plants, and now this one seems like it is going to die also. (Landgon, N.D.)

A: It was difficult to make an accurate diagnosis of the sample you sent in. However, I believe that it may have been a botrytis or powdery mildew that is causing the problem or, due to the curling leaves, the plant may have been exposed to a chilly draft.

It could be a combination of these factors as well. If you are misting the plants, stop; if they are near a window, move them away; if you are over watering, back off; and if it is not growing in a free-draining container, repot.

This is the best advice I can give a this time. Hope something helps!

Q: Can you tell me why the leaves on my global arborvitae are turning brown? I also have been trying to start a bur oak from acorns, but I haven't had any luck. Can you explain why? (Gettysburg, S.D.)

A: The global arborvitae is suffering from winter desiccation. Protect it in the fall by spraying it with Wilt-Pruf. This keeps the foliage from drying out. Respray again with the first late winter thaw to keep the spring winds from drying the foliage.

Bur oak need about 40 days of stratification with day temperature at 86 F and nights at 68 F. Under these conditions, the germination rate ranges from 28 to 85 percent, for an average of 45 percent. For every 10 seeds or acorns set out, on average, four to five would germinate. This requires lots of patience!

Q: I'm having a problem with my Norfolk Island pine. I have two of them, and it seems like every time I brush against them the fronds fall off. Do they need repotting and do they tolerate full sunlight? (Firesteel, S.D.)

A: The Norfolk Island pine is a poor bet as a houseplant of any duration in our part of the country. Native to the islands of the South Pacific, they need ample humidity to thrive.

They also need ample light—near a window, but not necessarily direct sunlight. Departing from either of these two important cultural factors will cause the fronds to drop.

If you can move the pines close to a window, mist them often with distilled water, and keep them well-watered during active growth, you may be able to drop any future leaf drop.

Q: I have four large evergreen trees that were planted in 1970, but since we had all of that snow, the one on the corner is drying up a lot. Is there anything I can do to save the tree? (Arthur, N.D.)

A: It is difficult to give you a solid answer on the information provided, but I'll take a stab at it being a spruce needlecast fungal disease.

This can be controlled by timely sprays with a product known as Bravo, making applications in early June and July. I suspect the trees may also be planted too closely, and if that is the case, removal of some may help the vigor of the remaining ones!

Q: Can you tell me how to get rid of the moss that is growing on my lawn? (Washburn, N.D.)

A: There are a number of tactics:

1. Core aerate.
2. Power rake.
3. Prune to allow more light.
4. Back off on watering in that area.

Q: Following is a technique for the person who was asking about transplanting bur oaks.

One of the easiest ways is to collect the acorns or nuts right after they have dropped to the ground and sow them a few inches deep at points where you want that kind of tree. Drive a stick or marker at each point to aid in finding the seedlings the following spring. Acorns with small worm holes probably won't germinate.

The Soil Conservation districts have been successfully planting bur oak seedlings in shelterbelts. I have several started that way. As I understand the technique, the young seedlings are root-pruned in the nursery row and may be replanted one or more times.

In 1960 I planted nursery-grown bur oaks. Years later a man hired a firm with a tree moving machine to move several kinds of my trees to his business place. One of these was a bur oak. There was complete success. Later four new bur oak whips came up from the removed oak and have developed into a very attractive group.

A: Thanks for the information on transplanting and seedling establishment. It will make interesting reading and good information to our readers.

Q: I have a question about my yard, but the problem is I live in Hawaii. The climate here is warm, but the area I live in is cool, and because we are slightly elevated we get a fair amount of rainfall, especially during the winter months.

I have a 36-square-foot "courtyard" with a 6-foot fence around it, so it stays shaded most of the day. I loosened the soil about 1.5 inches down and bought something called "shady lawn" grass seed. It has been about two weeks now and we have very nice growth. OK, here's my question: What is "shady grass"? What we have growing looks like a skinny blade of grass that grows straight up. It seems very frail, it is very easily pulled out of the ground with no effort at all.

I'm just wondering what it's going to look like. What can I expect out of it? Will it spread and withstand any amount of traffic? (Hawaii, e-mail)

A: From your description, it sounds like you are growing some creeping red fescue or rough bluegrass, as either would fit the description you provided. My bet would be that it is probably the creeping red fescue.

Generally, grass that is shade grown, even adapted species like the ones mentioned, are not as vigorous as grass grown in full sun and would not stand up to traffic as well. It takes some time to get a grass toughened up to the vicissitudes of what we are going to put it though. Mow it high, 2.5 to 3 inches, and alternate directions each time, to build a stronger, denser turf. Fertilize, but don't overdo it. Base the applications on the seasonal rainfall and how well your soil drains. I suspect that you have in excess of 60 inches of rainfall during the "winter season" and likely will have to irrigate during the summer. One to two applications of a turf fertilizer would likely do the trick. It is better to keep the grass a little on the lean side to promote toughness than to apply too much fertilizer and make the growth soft and susceptible to wear and disease problems.

You might want to check with the extension office in your state or county and see if they can provide more accurate information for you. I hope the information I provided helps you make some decisions.

Q: Can you tell me why my tulips have wide leaves and no stem for the blossom? I am wondering if they are too close together and that is what is causing them to not flower. (Watertown, S.D.)

A: Being too close is usually not a problem with tulips flowering. However, they are at the top of the list for bunny food, which makes me suspect them as the perpetrators of the damage!

It probably wouldn't hurt to dig them up and re-space them again either.

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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.

Source: Ron Smith (701) 231-8161 ronsmith@ndsuext.nodak.edu

Editor: Dean Hulse (701) 231-6136