February 21, 2002

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: I want to plant a lilac tree and flowering crab this year but need some advice about lilacs. Would it be best to plant hybrids or the old fashioned lilac? Would I need two for cross pollination? What kind of flowering crab would you suggest? I live 40 miles south of Fargo and in zone 3. (Rothsay, Minn.)

A: First the lilacs: It all depends on what you want, Fragrance? If so then the common ones are best. If fragrance isn't important, but vivid colors and mature size are, then go for the hybrids. You can have one lilac or 100; either way they will flower beautifully. Next, the crabapples. Do you want them for just the flowers with no or minimum hassle with the fruit, or is the fruit size, color, and durability important to you? There is only one completely fruitless crabapple, and that is 'Spring Snow', which is loaded with white flowers in spring, and no fruit. Then there is the 'Red Jewel', which is a beautiful, red-fruited, white flowering crab. The fruit shrivels and darkens with fall frosts, and remains on until spring, serving as a source of food for wildlife. Then there is the 'Thunderchild' crab which has delicate pink flowers and deep purple leaves. Again, one is all that is needed for fruiting, as there are usually plenty of other crabapple or edible apple species within a half mile or so for pollination and fruit set.

Q: I have a fiddle leaf fig near a sunny window. The plant leaves have now turned to grow towards the light. Is it okay to rotate the pot from time to time or is this too much for the plant? (E-mail reference)

A: Not a problem at all. It just might be easier for you to get a direct overhead light source so you wouldn't have to do that so often.

Q: A producer asked how to make his own carrot seeds. Could you tell him what he needs to know? (Napoleon, N.D.)

A: Since carrots are biennials, he has to leave them in the soil for a second year, making sure the crowns are protected with mulch going into winter. After winter, the carrot is then "vernalized" and flower induction takes place, with a seedstalk being formed. From there, he is on his own.

Q: I have a 25 year old ornamental crabapple that has gotten too big. I have tried pruning branches back to thin and reduce its height, but new branches sprout densely and grow very long during the next summer. I understand there is a hormonal balance between roots and shoots, so I spaded around the tree about 6 feet from the trunk, 8 to 9 inches deep, to cut roots. Still the branches sprouted. How can I get the tree reduced in size without it becoming dense with new, long growth? When should this be done? (Jamestown, N.D.)

A: There is a basic rule of thumb: to stimulate growth, prune when dormant; to slow or reduce growth, prune after leaf out. The idea behind this is that by pruning in late spring or early summer, photosynthizing material is removed, which reduces the vigor of the tree. Doing it just once will not do the trick. It must be done annually and sometimes twice during the season. The bad news about this is that pruning in summer or when the trees are actively growing opens them to disease spore invasion. Consequently, I would advise carefully selecting the time to do such pruning when there is no rain or high humidity and high temperatures forecast for a few days. Once these plants mature, and if they are healthy, their growth can be difficult to control, so don't give up.

Q: Do you have any tips on how to germinate and then successfully raise oak trees from acorns? I have a couple of acorns that I have stored in the refrigerator from last fall, and I would like to plant them this spring. When should I plant? How large a pot is needed, and given the size of the pot recommendation, how long should I leave the seedlings in them? How much growth can be anticipated in the first year? How should I store the seedlings to ensure that they will live through the next winter? (Fargo, N.D.)

A: When the soil thaws and is free of frost, plant the acorns about 4 inches down, where you want them to grow to maturity. I suggest planting two or three in each hole in case some don't germinate. Of course, if more than one germinates, then simply save the best one by snipping off the others at ground level. Planting them in containers is a good idea, but with the tap roots that develop on oaks, transplanting often causes some losses. You might want to put a protective cone around the planting site to keep the squirrels from getting to them. Since (I assume) you gathered the oaks locally, you need not worry about protection over the winter. They are completely hardy bur oaks that should take off nicely. I would protect them from rodent damage by surrounding them with a plastic or metal collar the first few years. Growth is hard to predict. It depends on the genetic vigor of the acorn. Usually, the first year is just to get established, so growth of about 12-18 inches should be all that can be expected, if that much. Be sure to sow the acorns in a sunny location.

Q: We have a large laurel willow in our yard that is about 30 feet tall. Beginning last summer, the leaves were much smaller and the tree started losing its branches in any type of high wind. They just snap off and fall to the ground. During the high winds on Feb. 11 the yard was full of willow branches that broke off the tree. Some of these branches are 2 inches in diameter, but snap like balsa wood. Should we have the tree removed? I am concerned that it may fall onto the house. (Fargo, N.D.)

A: I strongly urge that course of action. The tree is dead or dying and obviously has deadwood throughout. Better to be rid of it than to be picking up branches out of your living room or bedroom!

Q: Does a corn stalk just produce one corn cob? (Napoleon, N.D.)

A: Corn stalks often produce at least two, sometimes three, cobs. The second and third ones are smaller, sometimes down to the "nubbin" size, but still good eating.

Q: I have a peace plant that I have had for about five years. The problem I am having is that it was blooming when I purchased it, and hasn't bloomed since. I have fertilized it and repotted it over the years, but still nothing. It has gotten rather large and I would love to see it bloom. Any suggestions? (E-mail reference)

A: Give it more light, but not direct sunlight. Placing it near or next to an east window will often bring it into bloom in a month or two. Congratulations on having the plant for five years! Most people cannot keep a houseplant around that long.

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