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Hortiscope

Ron Smith answers questions about flowers, trees, gardens and shrubs.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: If my dahlia plants are in pots, do I need to remove them or can they be brought inside and kept in a dark and cool location? Also, should I wait until a frost has turned the top foliage dark? Any suggestions about geraniums? I have two pots that are really nice. (Fargo, N.D.)

A: You can leave the dahlia plants in pots and get away with it. However, I suspect the incidence of disease would be higher under those circumstances. I always wait until a frost blackens the top before moving them indoors. With your geraniums, you can bring them indoors and put them under plant lights on a 12-hour cycle to keep them through the winter. You also can prune them back and then dig them up. Shake off the excess soil and put them in a dark, dry location to try to hold them through the winter. Repot the plants sometime in late February or early March and then put them under plant lights on 12-hour cycles.

Q: I have a potted ficus tree that has lived on my front porch for four or five years. I live on the east coast of central Florida. I want to plant the tree in my backyard to block the afternoon sun. Is this a good idea? I have read some articles that say a ficus will grow quickly and be difficult to manage. I’ve also read some articles that say ficus trees are easy to care for and pose no real problems. Any advice would be much appreciated. (e-mail reference)

A: Any tree or shrub that isn't cared for on a regular basis can be difficult to control. A ficus tree is no different. I would go with the last opinion that you were given. Basically, some directions need to be followed when planting any tree. The tree needs to be properly sited. This means that the tree should be planted where it will thrive and not interfere with overhead lines or septic drainage fields or block clear visual access to motor traffic or a neighbor's space to any great extent. You need to consider a tree’s rate of growth and eventual size as it matures. "Cute" little plants from the nursery don't remain that way for very long if they are not taken care of. If you are going to place a tree where it will provide protection from the afternoon sun, what else will it do? Hang heavy branches over the roof? Not a problem if you anticipate that taking place and head it off with timely pruning. Waiting until the branches or the tree poses a threat is too late. Give a tree a chance to get established by keeping grass from becoming competitive with the roots for the first few years. An organic mulch will work, but don't overdo it. Three to 4 feet is enough to assist the tree roots and extend it out beyond the planting hole boundary.

Q: I am requesting an answer to a problem that has arisen about my cedar tree. My neighbor has asked me to cut my tree down because it is the reason he has a rustlike blight on his apple trees. My tree is not close to his apple trees, but it is within sight. I love all my trees and have really regretted every tree that I have ever lost due to storm damage or disease. Is there any possibility that there is any truth to my neighbor’s opinion? (e-mail reference)

A: There is truth to your neighbor's concern. Cedar (juniper) is an alternate host to the cedar apple rust fungus. The spores can be carried for hundreds of yards. While it is a nonissue on the cedar tree, it is a big deal on the apple trees because it debilitates the foliage and eventually leads the decline and death of the tree. The apple tree owner can control the development of the disease by timely spray applications of a fungicide applied at blossom time and after blossom drop and again 10 days later. You also can remove the fruiting bodies that show up on your cedar. By doing that, you interrupt the life cycle of the fungus and the apple tree does not become infected from your trees. Keep in mind that there may be other cedars in the area that could be the culprit. You happen to be close and are relatively easy to accuse.

Q: I’ve thoroughly enjoyed reading your information about willow trees, but the one answer I’m looking for wasn’t there. I am new to the art of bonsai, so every day I’m learning something new. One of my neighbors has a young weeping willow that I want to take a cutting from to grow a weeping bonsai. From what I’ve read, it seems the best willow cuttings are one-half to 1 inch thick and quite long. However, this wouldn’t be ideal for a bonsai. Could I take cuttings from some new shoots and start those? I would greatly appreciate any advice. (Pleasant Hope, Mo.)

A: I guess the reason you don't see much on bonsai trees in my columns is because I don't do it, so I don't know much about it. However, cuttings from new shoots of willow should root for you because willows are blessed with what are known as preformed root initials, so a cutting from the new growth (semihardwood) would or should work. If the cutting was totally succulent (no hardwood), then I doubt that it would have the ability to root. You might go on the Web to check out any sites that promote bonsai techniques. I believe many say that the true art is taking a seed and growing it as a bonsai. However, I could be wrong.

Q: I have a row of beautiful arborvitae growing along my lot line. Last year, it was very dry and two of them started looking stressed. I watered them as soon as I noticed. They now appear dead and another tree is showing the same symptoms. All of the other trees look great and have good growth. The local arborist could not see anything unusual with the arborvitae, but suggested that perhaps moles might have eaten away the roots. Any ideas? I do not want to lose any more plants. The trees appeared to just dry up. (Minnesota)

A: Moles only eat insect larvae and grubs in the soil, so they are not omnivores. They would not have touched the roots of the arborvitae. The death of these trees at random would indicate that perhaps bagworms got to work on them. More likely, this is spider mite damage because their activity increases significantly in hot and dry weather. If you want to counteract the effects of mite damage, a weekly spraying of the foliage with a hard spray of water would disrupt them as much or more than any insecticide would.

Q: How can I identify bagworm or spider mites? Are they visible on the leaves? (e-mail reference)

A: Bagworms are easily visible because they hang almost ornamentlike from the branches they are feeding on. Spider mites form minute webbing that is hard to see. However, if you take a sheet of white paper and hold it under an affected branch and shake it, if what falls is the size of a period at the end of a sentence and moves around on the paper, that is evidence of spider mite activity.

Q: I have a fir tree that is starting to lean. It is growing on the side of a small slope. I'm afraid if it gets much taller that it will fall over. I am wondering if I can cut the top 5 to 8 feet off and keep the rest of the tree. Will cutting off the top kill the tree or just stop it from growing? Thanks for your consideration. (New Hope, Pa.)

A: Cutting off the top 5 to 8 feet of the evergreen will not kill it. However, is it something you want to be looking at? I would suggest that you contact an ISA certified arborist to get some counseling and possible options before making the cut. Unless the root system has been physically limited or damaged, most trees are quite stable on slopes, especially the ones around your area. Go to http://www.treesaregood.com/findtreeservices/FindTreeCareService.aspx to locate an arborist in your area.

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.


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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