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Hortiscope

Ron Smith answers questions about plants, trees and gardens.

By Ron Smith, Horticulturist

NDSU Extension Service

Q.I have a tall rose plant that has not been pruned in years. I do not have a green thumb, but I would love to spread the rose’s beauty around my yard. It blooms about once a month. Can I prune and replant parts of the plant? I don't want to mess it up. I live in Florida. (e-mail reference)

A.You should have no problems with this objective. Cut the canes into 6- to 8-inch lengths, dip them into a rooting hormone and then stick them in well-drained soil so you can monitor their water needs. Do not let the soil (or whatever media you use) dry out, but don't keep it soggy. You should have some roots showing in six to eight weeks. Enjoy!

Q.I've always loved the fall colors on sugar maple trees. Fifteen years ago, I planted two sugar maples in the front yard. They have been doing well, except for the fall colors. Instead of the beautiful reds and oranges, my trees turn yellow and then brown. I live in southern New Jersey along the coast, but a good three miles from the saltwater bay. We are surrounded by what is called the New Jersey pine barrier, although progress has taken its toll on this last remaining forest. The trees are in full sun. I lime my yard every spring and fertilize the lawn four times a year. Our winters have been mild for the last 15 years, so I’m thinking that the trees are not getting enough cold weather. Should I give the trees more or less water? How about fertilizing the trees? The trees do not put out any seeds in the spring. (e-mail reference)

A.The first thing I would suggest is to get the trees identified by a local nursery this spring when they leaf out to be sure you are dealing with sugar maples. If they are sugar maples, back off on being so kind to them. They will show their genetically endowed potential for fall coloration when they are stressed a little. Trees as old as yours do not need annual fertilization and liming. Unless there is an extended droughty period lasting more than two weeks without any appreciable rainfall, the trees should not need watering. Make these minor corrections and your maples should start showing some good color next autumn.

Q.My plant is doing beautifully, except the edges of some leaves turn brown and die. Am I watering too much or too little? Is there some other cause? (e-mail reference)

A.Most problems come from overwatering. The problem also could be poor drainage, which causes anaerobic conditions in the soil or an accumulation of salts that causes foliar firing along the edge of the leaves.

Q.My parents have a large spirea bush. I would like to prune the bush without killing it. How much can I cut it back and when should it be pruned? They live in northeastern South Dakota. (e-mail reference)

A.They can be pruned very easily. Having gone so long without any pruning of significance, I would suggest going in and pruning about one-third of the largest branches back to the ground. This should stimulate new growth from the base when spring arrives. You could prune the whole plant late this winter or in early spring before new growth begins. The growth would be lush this year, but the bush would not produce flowers. Flowering would not take place until next year.

Q.I'm trying to find out the best use for ornamental orange fruit. The fruit is small and tart. I have a large, healthy plant that we bought two years ago thinking it was a lime tree. I live in Texas. (e-mail reference)

A.I really don’t know. I suppose you could coat the fruit with wax or shellac. How about making it into an alcoholic drink of some kind? Try contacting someone in the Texas Extension Service for any suggestions. Go to http://texasextension.tamu.edu/county/ and then click on the county where you live to make contact. Texans are very creative people, so I'm sure someone has come up with a practical use for this overly tart fruit.

Q.Four to five years ago, I planted 72 arborvitaes as a backdrop to the shadowbox fencing around the yard. The plants exposed to direct sun have grown well, but those in shaded areas have not. I removed four large white pines that opened up sunlight to many of the plants that have not grown well. These plants are alive, but not looking great. Can I expect these plants to grow or have they been damaged too much by not developing earlier? I am trying to determine whether I have to replace them or can expect them to respond to the change in sun light. Do you recommend any particular fertilizers to help rejuvenate these plants? Also, there are others plants that are shaded by a large oak that are in about the same shape. I am thinking of transplanting several of them to sunnier locations. Is this worth the effort or are they going to die during the transplanting process? (e-mail reference)

A.The plants should take off with growth when they get that infusion of more direct sunlight. As for the transplanting, every time it is done, the chance of dying exists and increases with age. My guess is that these plants are established in their current location, so it will be difficult to transplant these plants successfully. However, if you are not happy with their present location and performance, you really have nothing to lose by attempting to move them. You always can replace those that fail.

Q.Some of the leaves on my English ivy topiary are starting to turn yellow. It is in the plastic nursery pot it came in. Could that be the problem or what could be causing it? I mist it weekly and water when needed. (e-mail reference)

A.Try repotting the plant in a clay pot using the next nominal size larger pot. Use fresh potting soil and move it to where it can get a little more natural or artificial light. Check the leaves for possible spider mite damage because English ivy is susceptible to this pest. A stippled yellowing and some very fine webbing should be evident. Don’t overwater the plant. It is better to grow it a little on the dry side. A regular misting regime, such as once a week, will keep most spider mite infestations at bay.

Q.What soil should I use to repot my Christmas cactus? How do I know when it is time to repot the cactus? I've had it for years and never repotted it. It's flowering and looks great, although only half of the plant has flowers, which is weird. Last year, the whole thing flowered at the same time. (e-mail reference)

A.You are better off purchasing a high-quality, all-purpose potting soil mixed with about 30 percent sand or what is known as a bromeliad potting soil mix. Whatever product you select, be sure it is a good-quality product and has been pasteurized or sterilized. Try to resist the temptation to repot this plant! It thrives on being pot-bound to flower. If you think it needs soil, add some to the top of the pot. If you do repot, do not step up to a larger size. Wait until the plant stops flowering, then refer to the details on my Christmas cactus culture and care Web site at www.ext.nodak.edu/extnews/hortiscope/houseplnts/xmascctus.htm. Christmas cactus needs more than 12 hours of continuous darkness every 24 hours. Very likely, the part of the plant that is not flowering was exposed to low light that kept it from setting flower buds.

Q.I purchased a red bougainvillea that was in bloom. I planted it on the south side of the house in full sun. Now the plant has lost many leaves and many of those that remain are brown. Please help. (e-mail reference)

A.It sounds as though you planted the bougainvillea in the right location. The hotter and more sun these plants receive, the better. My guess is that the plant may not have been completely acclimated to the outdoor environment or that you got one that had a root rot disease. If you can get your fingers between the woody thorns and scratch the bark, check to see if the cambium is green beneath the outer bark. If it is, it likely will come back. If it is light green or brown to yellow, the plant is history. Take it back to the nursery and get it replaced with a healthy one. My experience with these plants is that they are trouble-free and grow a lot like scrambling, weedy vines. Bougainvillea usually needs regular, heavy pruning to get it to look its best and produce flowers.

Q.Are there perennial vegetables other than rhubarb and asparagus? If so, what are some other perennial vegetables? (e-mail reference)

A.Common perennial vegetables are rhubarb, chives, top multiplier onions, horseradish and asparagus. Everything else is an annual or biennial.


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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