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Don Kinzler, Published September 10 2010

Blanket is best way to winter strawberries

Q: Two years ago, we planted strawberries in our garden. They produced a lot of strawberries in year two and are pretty thick. Last year, they were not as thick, so we just wintered them by covering them with straw. What do I do to winter the plants this year? Do they need to be thinned out? Also, I always plant Norland and Pontiac potatoes in our garden and get a bountiful harvest.

The potatoes taste great, but always have a scab on the skin that is not very appealing. How can I prevent the skins from getting these scabs? (Park Rapids, Minn.)

A: Strawberries can be wintered with straw if you wish. However, any straw will have weed seeds that may become a problem the following year. I would suggest covering them with a Remy winter blanket. It works beautifully. It is a geotextile material that allows air and water through and protects against wide swings in weather extremes. Also, it isn’t as attractive for nesting rodents. If you cannot get around to uncovering it for whatever reason, that would be OK because the plants would not be adversely affected by big swings in temperature.

Scab on potatoes can be controlled by not growing anything in the potato (nightshade) family close to your potatoes. Use scab-free seed potatoes and don’t use the potatoes harvested from your field for seed the next year.

Maintain adequate soil moisture during tuberization. You can try to lower the pH level somewhat, but that usually is not practical in our Midwestern soils.

Q: I have a very old cottonwood tree in my backyard. I was digging around the tree to build a retention wall and found a clear, smelly liquid that seems to be coming out of the bark at the base of the tree. A certified horticulturist said the tree had bacterial wet wood and to keep an eye on it. I am hoping from what he told me that there will be clear signs as to when the tree has to come down.

I also know of Murphy’s Law. My wife is not very fond of this messy tree, but it provides great shade that has saved me significant money in cooling energy costs through the years. She would like for it to come down now. How can I tell how fast the disease is progressing, and is there a way to stop it? Is there anything I can do to prolong its life? (Centennial, Colo.)

A: The diagnosis by the local horticulturist is correct. The extent of the internal decay only can be determined by using an instrument known as an increment borer. It pulls a pencil-sized slice of wood from the interior of the tree to see if the heartwood is solid and there is enough supporting wood to keep the tree upright.

Unfortunately, there is no cure for this slowly progressive, annoying malady. This seepage also will attract insects, such as yellow jacket wasps at this time of year. As a horticulturist, I often find myself being a marriage moderator in situations such as this because the husband and wife are on opposite sides. What is more important to your happiness, a happy wife or shade and money saved on the cooling bill? You sound like a smart man to me, so I think I know your answer.

However, before giving in to her wish, explain every consequence of removing this tree. Many times we react to a situation like this without thinking it through all the way. You could take a chance by keeping the tree and hoping that her complaints will quit. However, what if she gets stung by a wasp or the tree topples in a storm, causing damage to your property? Making risky decisions isn’t easy. If it were up to me, I’d remove the tree after making sure your wife realized what the result would be. A new tree can replace this one. Good luck.

Q: A person I know had ant problems on rhubarb roots. To get rid of the ants, I suggested sprinkling corn meal around the plants. Ants cannot digest corn meal and will take it back to their hive. I have used this method with good success around my yard for the last five years. (e-mail reference)

A: This is one of the organic ways to control ants. I’ve never tried it but have heard other folks who have with good success.

Q: I just noticed a blog of some sorts of yours when I searched for Newport flowering plum trees. I want to ask a question because I seem to keep getting contradictory reports. I had a tree die in my front yard as a result of a bad winter here in south Florida. A person came out from my city and declared that it must be cut down. Also, per city regulations, I must replace it with another tree, so I have been searching for a replacement tree.

During the search, I found out about the Newport flowering plum tree. I like the fact that it won’t grow to enormous size because it will be close to my home. At the same time, it will provide shade for me. I also love that it can provide some fruit. However, I have heard conflicting reports about the tree being able to grow in south Florida. Will it do well in south Florida? Part of my requirements is a tree that doesn’t constantly need attention to survive and grow. (e-mail reference)

A: You need to contact your Florida Extension Service county agent. To find one, go to http://solutionsforyourlife.ufl.edu/map. The agent or a horticulturist at the University of Florida should be able to tell you if this particular plum tree will survive in your area.

Q: I have a grapevine growing in a pot. I’ve had it for three to four years. It came from grafted rootstock I bought in a nursery. I was just told that I need to prune the vine more than I have been. It has three visible main trunks (the graft line has been buried) and has not produced a single grape cluster. Can I get some advice on how to prune it and how to encourage grapes to grow or if there are any problems? (e-mail reference)

A: A grapevine in a pot doesn’t communicate sufficiently enough for me to give you good advice. If you’ve had it for that many years growing in a pot without planting it, I have to assume you live in a mild winter climate. So much depends on the variety of grape as to when it should be fruiting. In general, grapevines begin fruiting at about three years of age if planted in the ground. I cannot say for sure if keeping it in a pot impacts the setting of fruit. Here is a website, http://viticulture.hort.iastate.edu/cultivars/cultivars.html, from Iowa State University that has about the best information for reference purposes on a wide selection of grape cultivars.

Q: We had a tree service put two Laurel leaf willows in with a spade machine two years ago. The branches look very healthy, but the leaves are mostly coming in at the end of the branches. Since this tree is supposed to be very dense, I am a little concerned. Is there any type of soil treatment or fertilization I can do to help these trees? Thank you for your assistance. (e-mail reference)

A: Those are not happy trees and are not long for this world. I would recommend getting the stone mulch and any landscape fabric off and replacing it with bark.

Secondly, I’d get in touch with the tree service to see what it might be able to tell you about what is wrong with these trees. They look like they have excellent form, so they obviously were given good care in the nursery.

Generally, spaded trees will be set at the correct depth, so that shouldn’t be a problem.

Another possibility is your sprinkler system if you have one. Being in heavy clay, the soil will stay wet longer, so don’t overwater.

Q: Three years ago, I planted 32 emerald green arborvitaes. They took root and are doing great. I only lost one. The plants that were doing the best really took off and are so dense you cannot see through them. We have had a really dry summer with a few heat waves here in New Jersey. I came home from work Monday and noticed six or seven of those that were doing well lost color. They turned a light green just like that one that died. Each day this week, they were closer to brown when I came home from work. Today, they look like goners. Why all of a sudden am I losing them? It is frustrating. The trees get full sun. My only guess is they just couldn’t take the heat and direct sun they were exposed to.

This summer is really taking its toll on my landscaping. (e-mail reference)

A: It would be too easy to blame the weather for this loss after three years of getting the arborvitaes established and acclimated to your climate. Before you do anything rash, I encourage you to contact the Extension Service in your county. Go to http://njaes.rutgers.edu/county to find an agent nearest you. If you can get someone to come out for a site visit or send a sample and photos to Rutgers University for analysis and recommendations, that would be best. Once arborvitaes get established, they are pretty tough customers. They can live through a lot of abuse.

Q: I live in central Maine. I enjoyed reading your advice on growing tomatoes. A market gardener friend up the road told me that he prevents early blight by using a preventive spray of hydrogen peroxide and water. He uses one part hydrogen peroxide to nine parts water to prevent the blight. If blight does show, he uses one part of hydrogen peroxide to seven parts water.

I garden organically, so I don’t want to use fungicides. I mix the solution in a spray bottle and apply it regularly, particularly after a rain. So far, only some of my plants have shown a slight tinge of early blight. This is far better than years before.

Have you heard of this method? If so, how effective is it? Is it also effective as a preventive for late blight? Last year, the entire state suffered from a pandemic of late tomato blight. Previously, my tomatoes have been afflicted with early blight, but never late blight. I have dealt with early blight by rotating planting sites, cutting affected leaves and watering carefully. Despite the early blight, I always got a good crop of ripe tomatoes.

This year, I went on the defensive by being determined to beat out early blight.

There is not too much one can do organically for late blight. I am uncomfortable with the idea of using copper spray because it does have levels of toxicity and requires special handling. In late May, I planted 20 tomato plants in a sunny spot. I’ve never planted tomatoes there before. I spaced the plants farther apart than usual. Each planting hole was mixed with cow manure, bone meal and some organic fertilizer. I tried something new this year by mulching the entire bed with wide rolls of dark landscape paper. The tomato seedlings were planted through little slits I made in the paper. They’re doing great!

I’m not sure if the reduced levels of early blight have more to do with the landscape paper and brand new site than using the hydrogen peroxide spray. I hope they’ll ripen by late August and that we get a late frost. I also hope we don’t get trounced by late blight.

I read that you recommend water-stressing tomatoes to get them to ripen faster. Can you explain that in more detail? How often do you water them and when? By the way, organic gardening is huge in Maine. Small farms are springing up all around the state. A lot of this surge is due to the presence of the Maine Organic Farmers and Gardeners Association. (e-mail reference)

A: Thanks for the nice letter on your gardening techniques. Stop and think for a moment what you told me about hydrogen peroxide. The solution that is available over the counter is a 3 percent concentration. You will note that hydrogen peroxide is in a dark bottle and is recommended to be kept in a cool location.

This is because it is very unstable and reverts back to plain water after just a few hours of exposure. Your friend who is recommending the dilution rates is just using plain water. I’m too tired to do the math right now, but if it is diluted with seven to nine parts water, it seems to me that the actual amount of hydrogen peroxide in the mix would be minuscule.

Straight hydrogen peroxide at 3 percent will sanitize or sterilize surfaces and cuts on our skin. It also is used in some instances to sanitize the roots of transplants to temporarily assure that the root surfaces are free of diseases. Studies have been conducted to see what, if any, benefit the use of hydrogen peroxide would have on roses with black spot and powdery mildew. It failed in both instances.

Blights are limited on plants mostly through what you do, such as reducing dirt splash and plant spacing. You didn’t say if you trellised your tomatoes or allowed them to sprawl on the ground. Staking or trellising tomato plants will result in fewer disease problems and higher-quality tomatoes.

Any fruiting crop, such as grapes, raspberries, apples and sweet corn, will have a more intense flavor if slightly water-stressed. Tomatoes are no exception. Minor heat stresses and a little water deprivation result in more intense flavor and faster ripening. Watering should take place as the sun rises. How often is something I can’t answer. It depends on the soil and the meteorological factors that influence plant growth.

It is a judgment call that comes from experience. All the best to you.

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.