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Hortiscope

Ron Smith answers reader's questions about the world of plants, trees and gardens.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I am wondering about summertime pruning of apple and pear trees. I prune at dormant time (March/April). I was told this was the time to do it because the wounds were susceptible to disease and not healing right if done during the summer. Now I hear that summer pruning is done in southern states so regrowth and water shoots are not as plentiful. Is summertime pruning on apple and pear trees OK to do in Minnesota? Are there any drawbacks? (Benson, Minn.)

A.While summer it is not a recommended time to prune apple or other fruit trees, it is done by most homeowners, including yours truly! However, there are some important points to keep in mind. Major pruning should be done while the trees are dormant. Touchup pruning can be done during the summer to remove excess sucker growth or broken, diseased or scale-covered branches. Sometimes pruning also is done for safety reasons. If you are working with a tree species that is particularly prone to diseases, such as fire blight, then try to time the pruning while conditions are not favorable to disease development. Remember the disease triangle: susceptible host, virulent pathogen and environmental conditions that favor disease proliferation.

Q: I have a river birch in my backyard, but I would like to put a pool with a liner near the tree. The distance the tree would be from the pool is approximately 7 feet. It’s a gorgeous tree and is thriving. If I continue to prune the tree and the exterior wall of the pool is just outside the canopy of the pool, will I be able to keep the tree or will I have problems later on? (e-mail reference)

A: I have never known any river birch trees with roots that did any damage to pool or home walls. Keep this beautiful tree.

Q: I live in northeastern Tennessee. I purchased tulips that are blooming. Do I plant the tulips now or wait? Do I need to cover them with mulch and keep them watered? The temperature here tomorrow will be 70 degrees. (e-mail reference)

A: Plant the tulips now. No mulch is needed in your area of the country. Keep them watered, but be careful to not overdo it. Stop bragging about your nice temperatures!

Q: I have six spider plants, but only one of them produces babies. Five of the plants came in the same pot that my sister gave me. The plants without babies seem to be growing new plants from under the soil. My boss says they are male spider plants. Is that true? What can I do to help the plants produce stem babies? (e-mail reference)

A: The babies are produced on stolons that emerge from the mother plant. The plant produces the stolons when subjected to short days or long periods of uninterrupted nights. Some plants are more prone to produce flowers than others. There is no such thing as a male spider plant.

Q: I am not very educated about gardening, so I wanted to ask you how I should prepare my garden. My garden contains mostly phlox, verbena, petunias, marigolds, snapdragons, balloon flowers, violets and salvia. The dead plants are in the ground from last summer because I am not sure what to do with them. Is it best to leave the dead plants in the ground or should I pull them? What should I do to get the plants to bloom their very best? Thank you! (e-mail reference)

A: The plants should be removed and the soil turned over. Incorporate sphagnum peat moss into the soil. If you want to, work in about 4 pounds of 5-10-5 per 1,000 square feet for some nice, vigorous blooms.

Q: I live in southern Maine. I have a 4-year-old Annabelle hydrangea that I can't get to bloom. It was in a shady spot, but I was told it needed more sun. I moved the plant to an area with more sun, but it isn't blooming. It looks very healthy and grows each summer. (e-mail reference)

A: This vigorous species of hydrangea only flowers on new growth. If you can, get out fairly soon and prune the plant back hard. It then should bloom for you this summer.

Q: We planted flowering crab trees in our backyard in southern Minnesota. Before we could protect the trees, winter hit. A bunny paid us a visit and ate the bark up about 6 inches around the trees. What can we do to save and mend these trees? I would really appreciate hearing from you with any help that you could send. I have written to a lot of people, but heard from none. (e-mail reference)

A: I don't know why other people have not answered you because the answer is simple and sad. If the trees have been girdled all the way around by as much as you say, the trees are toast. You can expect a certain scenario this spring. The trees will leaf out with small leaves, but that is about it. There won’t be any enlargement or elongation of the leaves and eventually the foliage will dry. You can keep them in the ground and observe this if you wish or take them out of the ground as soon as the frost leaves and replant this spring. Remember to put some protective bunny wrap on the new trees before winter arrives. Be sure the wrap goes up to the first branch.

Q: I found your name on the Web. I have many emerald green arborvitaes planted in front of my home. They are beautiful, but they are very tall and getting wide at the base. I would like to prune them to shorten them and bring in the girth. Can this be done? If so, what is the best way to do it? Should the pruning take place over several seasons or years? I would appreciate your thoughts and expertise. (Cape Cod, Mass.)

A: Arborvitae can be pruned to shape and size, but should be done by someone who knows what he or she is doing. I suggest contacting a competent landscape maintenance company in your area. Check with your local Extension Service agent to see if he or she has a list of contractors to recommend. The landscape maintenance companies usually are licensed or certified. Be sure to check on that before allowing any work to be done.

Q: I was looking in one of my garden catalogs and saw a variety of peach tree (contender) that is rated for zones 4 through 8. “It has excellent cold hardiness and tolerance to late frosts," according to the catalog. I really would like to have a peach tree. Is this too good to be true or am I overly optimistic that this variety will survive and bear fruit where I live? (Jamestown, N.D.)

A: You will never know unless you try. Being on the edge of the "banana belt," you just might be able to get away with it and global warming also may be on our side. I encourage you to give a couple of them a try. Of course, let me know the results! If it works, I'll dig up more of my yard and plant some as well.

Q: I have at least 15 lilac bushes around my house. We haven’t lived here very long, so I am not certain if the bushes have been pruned in many years. There are suckers everywhere that look messy. I was going to go cut them back, but everything I’ve read says not to do it in the spring. I want them to flower this year, but things bloom really late here. We also sometimes get a killing frost even in the middle of June. We also have deer all over the place, so the bottoms are always bare because the deer eat the leaves. I am not sure what to do with them. Can you give me some advice? (e-mail reference)

A: Old lilac shrubs tend to sucker and there is nothing practical that you can do about it. Cutting the suckers to the ground is futile because they pop right back up again. With all the shrubs you have, applying Sucker Stop to all the cut surfaces would be worse than futile; it would be very expensive and not permanent. You could start a shrub replacement program. You could replace every other bush with a new cultivar that isn’t so prone to suckering. That way you can get the blooms you want from the old plants, provide protection from deer for the new ones until they get established and end up with something that will look good in a few years. There is no quick fix that I can recommend. Sorry!

Q: I was reading your jade forum and was quite impressed. I, of course, have a big problem. My father passed away. He was an incredible botanist. Unfortunately, I did not pick up those traits. I have inherited his jade plants. One is turning 56 and the other 53 years old this year. The plants have been low-maintenance and kept indoors for the most part. Last summer I wanted to encourage growth, so I moved them to our patio outside. We had a weather mishap and the 53-year-old fell over and broke in half. I've been in horror ever since. It seems the core rots when I cut it back. Any suggestions on how to save it? (e-mail reference)

A: Sorry to hear about the mishap. My guess is that you are keeping the soil too wet while you are trying to root the plant if I am reading what you said correctly. Are you talking about pruning the plant and then the stem rots after the cuts are made? I urge you to take small, 6- to 8-inch stem cuttings and allow them to dry for a day or two before sticking them into the soil to root. You also can do the same thing with leaves from the plant. The important thing is to perpetuate the plant through asexual propagation. That way it can be an original from the plant your dad was able to grow for so many years. It would be a shame to lose either plant.

Q: I have an old bur oak that started to produce acorns last summer. As the summer progressed, all of the acorns dried up. Do you have an idea why? (e-mail reference)

A: Some acorn insect probably destroyed the flower parts, so the tree was unable to complete forming mature acorns. Usually, these pests are not persistent if the tree is otherwise healthy. Unless you go through the same thing this year, I don't recommend any particular action other than normal sanitation/maintenance.

Q: I planted a Concord grapevine a few years ago. We had so much rain last summer that it seems the grapevine stopped doing anything. The vine lost all of its leaves and looked dead. I trimmed it back this winter (short). Was it wrong trimming it that drastically? What is the secret to growing grapevines? Is it because grapevines do not do well in Oklahoma? I would appreciate any help! (Oklahoma City, Okla.)

A: In general, the Concord grapevine should do fine in your part of the country. However, grapevines are very site specific for growth and production. The vine needs sunlight, good air drainage, modest soil fertility and no late spring frost. If the topography is undulating, the vine should be planted on the top of the rise. If a vine is exposed to a lot of wind forces, it will not do well. If your vine has been established for three years and didn't die this past summer, it should break bud and grow well this year.

Q: I have been trying to find a pruning technique for autumn blaze maples on the Web, but have been unsuccessful. I planted the tree a few years ago and it has grown rapidly. Maples have opposing branches at the same level and at close intervals on the main trunk. At first, this seemed like a very poor structure for strength, so I started to prune by leaving one branch at each level and spacing them around the tree. I was told by a nursery worker that this was all right. Later, another worker at the same nursery told me the natural structure of the tree was optimal. I am starting to believe that it's a losing battle to fight a maple’s natural growth habits. (e-mail reference)

A: The pruning of maples should be done in late spring or early summer. Winter or early spring pruning results in excessive bleeding. Prune to remove potentially weak branch connections. These would be any V-shaped crotches that are beginning to develop. Remove the weaker of the two or keep the one that has the desired growth characteristic that you want. Generally, these trees do not require a lot of pruning. Just remove branches that are crossing over or rubbing against each other, in addition to any that form the V-crotch. I would suggest contacting an International Society of Arboriculture certified arborist in your area to make some on-site suggestions or do the pruning for you. Every tree is a little different and must be approached based on the individual characteristics it possesses.

Q: I planted a common hackberry tree. That was before I read some negative things about the tree that the nursery neglected to tell me. I found your site and was surprised to find your positive remarks about the tree. I am replacing an ugly, dirty Siberian elm. I hate Siberian elms because the trees produce millions of seeds. Once the trees reach a certain age, parts die continuously. What I want is a tree that is nice and will provide quick shade. I hope the hackberry will not be as troublesome as the Siberian elm. (Utah)

A: Keep it. The hackberry will be such a big improvement over the Siberian elm that you will find it hard to believe. Hackberry wood is tough and the nutlets are prized by the wildlife, especially squirrels.

Q: I inadvertently left my spider plant (given to me by my parents 20 years ago) outside this weekend. I live in Connecticut. We had awful rains and a big drop in temperature. Now the leaves are brown and hanging over the pot. (e-mail reference)

A: I recommend patience to see if it will recover. There is nothing you can do other than remove the dead or brown leaves with scissors. If the temperatures did not get low enough to kill it, chances are you will see new growth emerging from the crown in two to four weeks.

Q: I have a large, established calla patch in my garden. Last fall I noticed many seed pods that looked almost like small cobs of corn (I don't know the proper name and term for them) I collected a number of the pods and carefully dried them out. Now I have 70-plus sprouted calla plants. Will they flower this year or will it take another season? (e-mail reference)

A: Since I have no direct experience, I will give you an educated guess. The calla probably won’t flower this year or the following season. Energy is required for flowering (reproductive cycle), which often requires a season or two to accumulate to a level sufficient enough to produce flowers.


NDSU Agriculture Communication

Source:Ron Smith, (701) 231-8161, ronald.smith@ndsu.edu
Editor:Rich Mattern, (701) 231-6136, richard.mattern@ndsu.edu
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