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Ron Smith answers questions about plants, trees and gardens.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I think what I have is a crown of thorns plant that is several years old. All of a sudden, it is droopy, losing leaves and turning yellow. How can I revive this plant? (e-mail reference)

A: A crown of thorns plant is almost indestructible. The only things I know of that take this plant down is too much water or the temperature is too low. If the plant is or has not experienced either or both of these problems, then I don’t know what is wrong. Sorry!

Q: I've had my jade tree for two years. I am very careful with it and assure you nothing drastic has happened. It did overcome a mealy bug infestation. However, the leaves have turned very maroon or red and fallen off the plant at the base. The top of the jade is growing new leaves. I am very concerned because my jade hasn’t dropped leaves before. What's wrong with it? (e-mail reference)

A: Do you have any hair falling off your head? I do, but I'm not bald. What this likely means is the leaves are going through normal senescence. This could be due to the law of limiting factors for plant growth. Considering the environment the plant has been in the past two years and that it is putting on new growth indicates that this plant is shedding the old, photosynthetically inefficient leaves. In other words, out with the old and in with the new! I don't think you have anything to worry about. The plant will reach a stage of stability at some point, with the leaf growth matching the leaf drop, unless something is done to increase the light intensity and/or duration.

Q: I have a crown of thorns that has been growing well for a number of years. However, the leaves are turning yellow and dropping off. I lose about 10 to 12 leaves per week. Following the most recent flowering period (quite profuse), many of the leaves (30 or so) quickly turned yellow and dried up. Most of these leaves were on one side of the plant. I have been watering it weekly and turn the plant about a quarter of a turn each week to give it equal lighting (the plant is in a south window). I also have a tall hibiscus next to this crown of thorns. The hibiscus recently became infected with small white aphids, so I have isolated it and treated it with a spray. Could the crown of thorns also be infected? If so, are these two instances related or are they separate problems? (e-mail reference)

A: The two events probably are unrelated or else you would have observed the aphids on the crown of thorns as well. Winter leaf drop is somewhat common with this species of houseplant because of less light being available and too much water. Keep in mind that this is a succulent that has the ability to store water. With the cooler temperatures and lower light availability, it is easy to apply too much water. Given the absence of any piercing-sucking insect pests, this plant should recover if you back off on the watering and supply supplemental lighting for 12-plus hours a day. The other possibility is to be patient until spring arrives so you can plant it outdoors.

Q: I have an old sugar maple near the sidewalk in front of my house. The tree is very old. One of my neighbors a few years ago decided to start tapping neighborhood trees to make syrup. The neighbor does all the work, but splits the syrup with us! It's a hard offer to pass up. However, the tree was distressed when we first bought the house, so I've been trying through the years to help it come back by having it professionally pruned and deep-root fertilized. Lightning once struck the center mast, so that is gone. It produces a surprising amount of sap. However, given that I'm trying to get the tree to recover, I don't want to deprive it of its lifeblood. The bark gets spongy, crumbly or moldy at times, which could be related to the weather or something else. Does tapping a tree for syrup help or hurt it? I have a feeling there are more factors in play than just a quantity of sap reaching the limbs, but maybe it's that simple. (e-mail reference)

A: Normally, tapping a maple for syrup every spring will not cause any problems to the tree’s health. However, from your description of the situation, I would encourage your tree tapper to give the tree a break and not go after the sap until you can get the tree's vigor back. I would encourage you to check with a horticulturist at the county Extension Service office in your state. Go to http://www.csrees.usdA:gov/Extension/ and click on your state to get some names and phone numbers of people who could help. We don't have sugar maples of any consequence in North Dakota. We have boxelder maples, which some folks tap and convert the sap into maple syrup. While I'm sure it is not as good as the real thing from a sugar maple, we are satisfied with what we have!

Q: We have a young plum tree that may be a Santa Rosa. It appears healthy and happy in our yard. It blooms beautifully and sets tons of tiny fruit. However, as the summer goes on, the little fruit (size of a blueberry) drops off and we end up with two delicious plums. What is happening with this tree? Is the problem age, nutrients or pests? I'd appreciate any information you can give us because we can't wait to get more than two plums a year. Would we benefit from planting another plum tree? If so, what variety would be a good companion in an area along coastal New England? Unfortunately, I haven't had much luck with our local Extension Service. (e-mail reference)

A: Even though the Santa Rosa is a self-pollinator, it probably will never be a great producer unless you get another Japanese plum to cross with it. Try to find a gold, red heart or shiro for this purpose. Sorry you've had trouble getting information locally.

Q: I have two Hansen cherry bushes and three Nanking cherry bushes. How do you prune these bushes? When is the best time to prune (northern Wisconsin)? How harshly can we prune them without damaging the plants? The Hansen’s were chewed down almost completely in the second year by deer and now have bushed out uncontrollably. Last year, we had thousands of beautiful blooms and enough cherries for a small pie. (I hit the roots with the tiller, so the plant struggled some. The Nankings were strong plants last year, but didn’t have any blossoms. We’d like to make use of the fruit as it comes. (e-mail reference)

A: Basically, prune them to remove the oldest wood each year. Prune the bushes back to the crown. The bush that was ravaged by deer probably will be the first to send up suckers, which may or may not be a blessing to your planning. Let this chewing by the deer be a lesson about overpruning. As for the timing, late winter/early spring is best. Just be sure it is done before leaf break takes place. If they start getting too rowdy in their growth, you can do a summer pruning after the fruit is harvested.

Q: My cyclamen plants that I bought in October are doing well. I know that I am supposed to discard the flower stalks after blooming, but I waited too long so I cannot tell which are spent and which might be getting ready to bloom. There are several healthy stalks with very round heads. Others have smaller heads, but I am sure they are going to bloom. (e-mail reference)

A: I don't know what to tell you except wait until the blooming starts and then remove those stems that are not.

Q: We live in Colorado at almost 7,000 feet. The sand cherry tree that we planted has been doing great. The offshoots are about 3 feet from the base. Can we dig them up and transplant the roots somewhere else? (e-mail reference)

A: I love easy, one-word questions like this. Yes!

Q: About 10 years ago, I planted a row of emerald arborvitaes down both sides of my front yard. Last spring, my neighbor had a dead tree that fell on my property and destroyed several of my trees. The remaining trees are about 6 feet tall. I have extras that I planted in the backyard that I can move to the front. How do I go about doing this? Can the established trees be moved? Can this be done with a shovel or will I have to bring in a professional with heavy equipment do this for me? I miss my privacy fence! (Arkansas)

A: I would employ the services of a landscaping company to do the digging and moving by hand. Large, tree-moving equipment should not be needed for arborvitaes just 6 feet tall. Make sure you get a hold of a reputable firm with people that know what they are doing.

Q: Spring is fast approaching, so I’m getting ready to plant my garden with vegetables. However, my cats have used the garden as a litterbox. I have cleaned the garden, but I am worried about parasites in the soil. Is there anything I can add to the soil before I plant to ensure that there won't be any health issues? I plan to put up fencing to try to keep the cats out (easier said than done). (e-mail reference)

A: I would think your garden soil would be safe for vegetables, such as corn, tomatoes, beans and cabbage. In other words, plant anything that is not a root crop, such as carrots or radishes, for just this year. Soil has a wonderful way of breaking down things we consider offensive or health threatening and rendering something of value for growing plants (vegetables or weeds). Good luck at keeping the cats at bay. If the fence plan falls short of the objective, I suggest a couple of motion detection sprinklers around the garden because cats hate getting wet. These impact sprinklers come on suddenly to scare and wet them down. However, you have to remember that as well when you are approaching the garden, so be sure to turn the water supply off before you do!

Q: I have several arborvitae shrubs we have by our home south of Pukwana, S.D. Most are on the west and south sides of the house. The shrubs are getting too big because I’ve never pruned them. I would like to trim off a foot or so to get a better view from my windows. Please advise what is a safe time and amount to prune so there is no damage. Also, we have two arborvitae trees that are on the south side of the house. They also have never been pruned. I am satisfied with the height they are at right now. Can I annually prune the trees to keep them at this height? (e-mail reference)

A: You can go ahead and prune the shrubs and trees to your heart's content. Be sure to leave some green behind to get new growth regenerated. Do this in the spring just before new growth begins. Doing this should cover all the pruning with a fresh new look.

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

NDSU Agriculture Communication

Source:Ron Smith, (701) 231-8161,
Editor:Rich Mattern, (701) 231-6136,
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