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Don Kinzler, Published November 02 2012

Hortiscope: Pruning needs vary depending on plant

Q: Now that we have had frost and are at the end of the growing season, is this the time to trim or prune clematis, honeysuckle and trumpet vines? If so, how much should I trim or prune?

All of the plants have had three growing seasons. The honeysuckle has done the best. However, it is top-heavy. It has some protection, so it still has flowers on it. (email)

A: Coming into winter or coming from winter into early spring before new growth begins are good times to prune any of these vines. The clematis should get the lightest pruning. Remove no more than one-third of the woody vine between now and next spring. Excessive removal of woody stock will cause it to put energy into producing new vegetative growth, so there would be very little flowering. Prune lighter than you think at first to see how the vine responds next season. After that, adjust to suit your interests.

Since you didn’t mention which cultivar of honeysuckle you have, I’ll assume that it is the species lonicera japonica, which can become quite the rampant grower. Again, sometime between now and next spring but before it breaks dormancy, cut it back to keep it within your desired bounds. I promise you won’t hurt it. Get rid of the oldest, most woody parts first and then trim the newer woody growth to suit your intentions.

Same goes for the trumpet vine. Both of these vines can sneak up on an unwary homeowner. Before it is realized, the vines take over a landscape like a Godzilla monster. You’ve succeeded in getting them established, so congratulations. Just stay on top of them with annual late winter or early spring pruning.

Q: I have about 400 feet of Peking cotoneasters. However, the local nursery says they have fire blight. Through the years, I have cut off the bad stuff, but it spread a lot this year. I did some research and found that one remedy is to cut them down to about 12 inches, which I did.

Is there something else I should do such as spraying them with something? (email)

A: You did the right thing by pruning the hedges back to about 12 inches and disposing of the cuttings.

Prior to bud break next spring, you should apply an antibiotic such as streptomycin or a fungicide containing basic copper sulfate. Continue to spray at intervals of five to seven days until blooming is completed.

During the summer, prune out immediately any diseased shoots that show up. Don’t fertilize because it encourages lush growth that is susceptible to the bacterium. If you fertilize your lawn adjacent to your hedge, give yourself a clearing of about 10 feet from the hedges where no fertilizer is applied.

Cotoneasters are one of the more susceptible species to this disease, so it will require careful monitoring and management on your part.

Q: I have lilacs in my backyard. Nothing grows very well near them, including my hardy impatiens.

I have just had the cement in our front yard dug up, and I want to plant various flowering bulbs in the area around the lilac that I transplanted there six years ago.

Will they grow or are lilacs very piggy plants whose roots won’t allow it? I’m more than willing to dig up the lilac and return it to the backyard. However, I love the idea of lilacs blooming in the front yard. (Brooklyn, N.Y.)

A: Go ahead and plant the spring-flowering bulbs. Daffodils and tulips will give you a nice splash of color prior to the lilac getting around to flowering.

There should be no problem from the roots of the lilac as long as sufficient water is provided for all the plants.

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 email ronald.smith@ndsu.edu.

For answers to general

horticultural questions, go to www.ag.ndsu.edu/horticulture.

Q: I have a problem with our maple tree that we planted four years ago. This spring and summer, we noticed the bark splitting and peeling back. It started low on the north side of the tree and has progressed up the tree. Most of the damage is now on the south side of the tree. The tree was doing well prior to this year. It did not leaf out completely this spring. I have attached two pictures of the damage. Can you give any advice on the prognosis of the tree or what we can do? It is heartbreaking to lose a tree. My husband has been feeding it regular doses of vinegar when watering to help the soil composition. (email reference)

A: Thanks for the excellent photos. This kind of bark splitting is not normal. The tree can be protected from this problem by being a little less nice to it. Keep it watered through droughty periods, which is about all it should need. Take a pruning or other sharp pocket knife and cut back to where the bark is attached. Next, go to a local hardware store and get some Kraft paper tree wrap and wrap the tree for the winter months. Leave the wrap on the tree until the tree begins to leaf out next spring. Then allow the tree to begin to callus over. Don’t apply any tree wound dressing. I see that the base of the tree has grass growing up to the trunk. This needs to be corrected by carefully removing the grass back at least 12 to 18 inches and putting a layer of organic mulch about 3 inches thick around the base. Splitting like this can be caused by a combination of events that are caused by nature and humans. Wide fluctuations in water availability and temperature swings can initiate this problem. Minimize pruning for the next couple of years, especially on the south and southwest side of the tree. Make it a point to wrap your tree every fall at this time for at least the next three or more years to get a thicker, corky bark developed that will be resistant to such damage.

Q: I read an interesting article about a gardener in the Fort Yates area who does no-till gardening. I was taught to clean out the garden thoroughly to prevent disease buildup from the remaining plants. What’s the thought on this from horticulture people? (email reference)

A: My judgment is that it is another approach to gardening. There are many variations to it, but it basically is built around killing everything off with glyphosate or by covering existing vegetation with a light-proof tarp, cardboard or newspaper to get the vegetation killed. It isn’t an easier approach, in my opinion, because it requires special tools to plant the seeds. I think it probably will survive as a novel approach to gardening. Adherents say it is the only way to go in vegetable gardening. My concerns are around litter cleanup, especially where diseased or insect-troubled produce gets left behind. I also think that no-till would be limited in scope to radishes, lettuce, Swiss chard or a few other crops. How can it be no-till when one is working with sweet corn and potatoes? Tilling is required to harvest the potatoes or removing the corn stalks. Call me old- fashioned, but I like clean cultivation and a cover crop, such as oats, being sown to add organic matter or well-weathered compost. My wife and I have practiced square-foot gardening for more than 25 years with very satisfactory success. The idea of no-till vegetable gardening holds little appeal to me. So far, home gardening is unregulated, so the choice is up to the individual on how to grow fresh produce. The important thing is to pursue vegetable and fruit gardening for the benefits, no matter the method chosen.

Q: I have a jade plant I bought 35 years ago. It was big and beautiful and had three main trunks. About 30 year ago, one of the trunks rotted. I cut it off and put it in a smaller pot. The other two trunks were healthy and growing normally. It was really pretty and looked like a huge bonsai. One day, I saw black, moldy spots on some of the leaves on one trunk. I removed the leaves and tried soap insecticide. However, it got really bad, so I had to cut more off to keep it from spreading. The main plant, even with one huge trunk, was pretty, but the new leaves that grew started coming out deformed. They are bumpy and some are shaped like a heart. I pinched off some of the heart-shaped ones, but most of the rest were bumpy. However, it still looked OK. About a year ago, it started sprouting leaves through the old, main trunk. Branches grew from the sprouts and they sprouted new limbs, too. One branch rooted in the soil and was sprouting new limbs. It’s still sprouting everywhere. I feel like it’s telling me it wants to live. It looks awful now because the branches have twisted around each other and there are too many of them. I know I have to choose which ones to take off and probably remove all the new plants that started growing in the soil around the main trunk. It is hard for me to trim things off and let them die. I will end up repotting them and having more jades with deformed leaves. The plant is huge and heavy, so my husband would like me to throw it out, but I can’t. Where I live it’s too cold to plant it outside. Do you happen to know what the black mold that appeared on the leaves is and where it could have come from? Do you have any idea why, after 35 years, it started sprouting like mad? (email reference)

A: The black spots were some kind of fungal infection that somehow got started due to some aberration in cultural practices or environmental shifts. I am more concerned with the way you are describing the growth of the plant. It sounds as if a growth-regulating gas is impacting the plant somehow. It could be ethylene or a natural gas leak. Do you have the plant anywhere near fruit that would be ripening and emitting this gas? Have you had your furnace system checked for natural gas leaks? Something with hormonal activity is causing this goofy growth. For the sake of good health, I suggest that you get your heating system checked. If that turns out to be OK, then something in the structure of your home, furniture, carpeting or whatever is causing this unnatural stimulation.

Q: As the area’s lawn guru, I am turning to you for some advice on a topic that has a lot of different opinions. I use the Scotts four-step granular fertilizer process. However, I have missed the boat on step four because of the mild falls the past few years or the store selling out. This year, I have it covered. I have been told to apply it immediately before any snowfall that will stay on the ground for the winter. Others suggest applying it anywhere from now until the ground freezes and right before a good rain. The lawn, like most lawns this summer, is stressed because of the dry conditions. (email reference)

A: Apply it just before a rain. If you wait until permanent snow cover is about to arrive, the soil may be frozen, so the nutrients may not get into the vascular system of the grass plants. Getting it down now is more or less like a flu shot because it provides protection against Mother Nature’s hard winter.

Q: I am looking for some advice about a row of spruce trees (unsure what type) that I believe were planted about 1970. They appear to be healthy. The problem is that the previous owner planted them 3 to 4 feet apart, so the trees grossly overlap each other to form a literal wall of spruce. These trees separate my property from the next door neighbor. He would hate to see them cut down because they do provide a good privacy screen. My problem is the fact that I want to build a garage on the lot on the same side as these trees. Should I be worried about these trees falling over onto my garage? How many more years do you think I have before they would need to be removed? The estimates to remove them ranged from $6,000 to $10,000. With this in mind, I prefer to keep them. However, if they are a risk, I need to remove them. Thinning out is not an option because the sides of the trees would be exposed and look awful due to the lack of greenery and shape from being planted so close. (Calgary, Canada)

A: If they have stood that long against what Calgary has gone through in the last 42 years, you have nothing to worry about. Spruce trees of all stripes are known to be durable and highly wind tolerant if they are properly planted and established. Yours are well-established. It would take a tsunami to move them because the branches and roots are intertwined. Man couldn’t build a more durable windbreak out of anything else. It is not unusual for a wall of spruce like you describe to last well beyond 100 years. However, nothing is guaranteed. You should communicate with your builder that the trees need to be protected during construction. This would involve not having the roots run over with heavy equipment or the branches getting broken off. The builder would need to put plywood or steel plates over the area where the heavy equipment would be running to spread out the compaction pressure. I would encourage you to be present for as much of the construction process as possible to be sure there are no shortcuts taken.