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Don Kinzler, Published July 02 2010

Pick smallest peaches to strengthen tree

Q: I planted a Georgia young belle peach tree last year. This year, it flowered and has many small peaches on it. The tree still is young and weak, so should I take some of the peaches off the tree so the branches don’t break? If I should, I’m not sure when to do it. (e-mail reference)

A: Pick off the smallest peaches and leave one or two, at most, on a branch.

Like most youngsters, they can get themselves into trouble easily by being overzealous. Just be careful in removing the small peaches. Do it with a sharp hand pruner or pinking shears instead of pulling them off.


Q: I am looking for a purple flowering crabapple tree for a boulevard planting.

The more resistant to diseases it is, the better. I am located in a small town between Watertown and Brookings, S.D. I enjoy your columns in the “Green Sheet” from the Aberdeen American News. (e-mail reference)

A: Some selections to consider are the royal raindrop (red foliage and fruit), prairiefire (green foliage and maroon fruit), thunderchild (deep purple foliage with dark red fruit) and velvet pillar (purple foliage with sparse, red fruit).

Thanks for the very kind words about the column!


Q: My husband and I are looking to plant a few deciduous trees in our yard. We live north of Mandan in a rural subdivision. It’s fairly flat, but we are on a hill, so it’s usually windy. I was just wondering if there are some trees that are more resistant to wind. I would prefer a maple species if you think that’s a possibility. However, there are so many to choose from. The trees I’ve been looking at are the sienna, burgundy belle and crimson sentry. I’ve pretty much concluded that the crimson sentry won’t work but am not sure about the other two. Are there any other suggestions? We have several spruce trees and also lots of lilacs but would like to add to the mix. (Mandan, N.D.)

A: The toughest trees for a windy setting are the hybrid poplars. The sienna is the only one with a chance to make it in your area. It is a cross between a silver and red maple. It is hardy down to Zone 3, while the other two are not.

The old hackberry is crowbar tough, as is the new centennial elm.


Q: I have a big box elder tree in my front yard that has a lot of roots sticking out of the ground. What time of the year can I cut these out? (Bandera, Texas)

A: Cut out the worst roots, but only as much as you need to keep them from protruding onto the surface. Keep in mind that the roots keep the tree stabilized. Removing too many roots would weaken the tree’s stability during a storm. You can do it now or any time you feel so inclined.


Q: I have a dieffenbachia plant that I rescued from a supermarket. It was doing wonderfully for more than a year. However, all the older leaves have turned yellow, so I removed them. But all the new leaves are coming out tightly curled and do not open up. Any suggestions? (e-mail reference)

A: I would guess that it could stand to be repotted. Get some potting soil and a new well-draining pot at a local garden center. The new pot should be one size larger than the one you have. If the roots are encircling and tight, take a knife and cut into them to encourage movement out of the tight ball and produce new roots in the fresh media.


Q: I live in north Fargo on a typical city lot. I miss the fruit trees I had when I lived in zone 6. I would like to grow fruit. However, I don’t have room for two each of apricot, pear or plum trees. Can I use a bush apricot, sand plum or some other type of bush for cross-pollination? Is there a variety of cherry that will produce up here? Would it require a cross-pollinator? (Fargo)

A: Are you living in an isolated location away from neighbors and other landscape plantings? I’d bet not, so I am willing to say that somewhere within a quarter of a mile radius are plenty of similar trees that can serve as cross-pollinators. The only exception might be pears because they suffer from iron chlorosis and fire blight problems in our area.


Q: I have two houseplants with mold problems. One has yellowish mold, while the other has whitish mold in the soil. Both plants seem healthy and neither seems to have mold on the plant. I thought I’d killed off the yellow mold awhile back by letting the plant dry almost completely (it’s a tough little hoya). I repotted it last year, and the mold returned with a vengeance. Can you recommend a good fungicide to put in the soil of these plants? I worry the mold may spread to my African violets. (e-mail reference)

A: This is a saprophyte problem, not a parasite. It is working on digesting the organic matter in the potting soil. This is nothing to worry about from the plant’s point of view. If you are concerned, repot the plants again using a new or clean pot and heat your potting soil in a microwave for about four minutes to pasteurize everything that is in the media.


Q: I have a large eastern cottonwood in my backyard. I love this tree because it provides a lot of shade for my house. About two months ago, big pieces of bark started falling off the upper branches. Some branches are pretty big. I called a local tree and turf adviser who said the tree had borers and larvae. He recommended removing the tree and nothing else. About half the tree is still alive. I would like to save the tree, so is there any way to spray for this problem? If the tree is removed, will these borers move to my other cottonwood and pine trees? (e-mail reference)

A: A half-dead tree is not something you want to try to save, especially one that is infested with borer larvae. Get the tree removed as soon as possible by a qualified, insured and bonded tree expert. At the same time, have the surrounding trees checked for insect infestations so that remedial action can be taken before it gets too late as it is with your cottonwood tree. I wouldn’t waste any time. I don’t mean to scare you, but the possibility of a large tree falling and damaging your house or a loved one isn’t worth debating.


Q: I purchased and planted two blue spruce trees. While they were being loaded at the store, the very top branch that sticks straight up broke off one of the trees. I didn’t think much of it at the time, but now am worried that the top vertical branch might be responsible for the tree’s growth. I’m not a tree expert, so I could be wrong about how the tree will grow taller. Without the center vertical branch, will my tree have stunted growth? The tree also was oozing a little sap where the top branch broke off. To protect it from insects, I put some tape on it. Should I leave it exposed to dry up and heal? (e-mail reference)

A: First, get the tape off the tree and then stop worrying about the future of the tree. One of the lateral branches, probably the longest one, will curve up and become the central leader with only a little crook in the stem to show for it. In time, the little crook will not be as noticeable. Sap flow in all living trees is normal at this time of year, so don’t worry about that.


Q: My iris leaves are getting a light yellow color. It has been cool and wet here in South Dakota. I transplanted the iris plant and have not had it bloom in two seasons. Did I plant it too deeply? Do I need to apply some fungicide? (e-mail reference)

A: You probably planted it too deeply and possibly overwatered it. Dig and reset the plant. While you are doing that, cut off any decayed rhizomes back to fresh, disease-free flesh. Fungicides are not needed if you follow this procedure.

Also, make sure the plant gets at least a half day of direct sunlight.


Q: I live in the Niagara region of Ontario, Canada. I had purchased thuja whipcord last spring. I had not decided on a permanent location for this evergreen, so I kept it in a large container. Close to winter, I made sure the soil was dry and put the container in my sun porch. During a warm spell in March, I brought it outside where it was exposed to several mornings of frost.

What looked to be a successful winterization quickly turned the thuja into a dry and browning shrub. I really love this plant, so its there a chance that it will survive? I now fertilize it every two weeks. (e-mail reference)

A: The mistakes you made in judgment about the right things to do, such as allowing the soil to dry and bringing it indoors, is what killed the tree. It would have been a better choice, since you were uncertain as to where to plant the tree, for you to plunge the pot into the soil and give it a good soaking before the winter freeze took place. A hydrated plant has a much better chance of surviving low temperatures and wind stress than one that is lacking in sufficient water in the cell tissue. I’m afraid that you are wasting your time watering and fertilizing it. You are better off throwing this one out and getting another one once you have decided where to plant it.


Q: I have a ficus hedge that has about a 5 percent leaf infestation by a dark, crawling insect. It lays tiny white eggs enclosed by a leaf. Can you tell me the insect and what form of insecticide would reach this pest? My gardener said he has sprayed twice, but there was no improvement. (e-mail reference)

A: You need a systemic insecticide to control whatever this pest is. Look for a product that contains the active ingredient Imidacloprid. Bayer has a product on the market known as “Bayer Advanced Tree and Shrub Insect Control.” There are other brands that carry the same ingredient if the Bayer product is not available where you shop.


To contact Ron Smith for answers to your questions, write to Ron Smith, NDSU Department of Plant Sciences, Dept. 7670, Box 6050, Fargo, ND 58108-6050 or e-mail ronald.smith@ndsu.edu.