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

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I'd like to know why my rhubarb is not growing as much this year as it has in the past seven years. Please tell me what I should do. (e-mail reference)

A: If you have not divided the rhubarb plants during these past seven years, that is what you need to do. Rhubarb should be divided every three to four years to keep it growing vigorously.

Q: I have a friend who is trying to grow a blue spruce from a seed taken from a fallen tree. Is this possible? She has tried a few, but they did not start to grow. She has one that has sprouted, but looks like a piece of hay (brown, with a few extensions from the stem.) It is in a small pot and she feeds it water and liquid food. What can she do to make it work? (e-mail reference)

A: Spruce seeds have to be harvested when mature. The seeds then have to be scarified and stratified for a few months. The approach that is least frustrating is to plant harvested seeds outdoors in the fall. The ensuing weather will do the work for you by scarifying and stratifying the seeds. If the seeds don't get eaten and are viable, they should germinate and grow. You don't need to add any fertilizer to the seeds or seedlings if they are growing in typical mineral soil. Another practice is to store the seed in a container filled with a 50/50 mix of sphagnum peat moss and sand. The soil should be damp, but not soaking wet. Place the seeds in the refrigerator for a couple of months. Plant the seeds in the fall and be sure that the soil stays moist going into winter. Usually, germination will take place within a few days. Protect the freshly emerged seedlings from nibblers through the winter months.

Q: I live in Iowa. I am wondering how to keep weeds out of my grapevine. I pull the weeds out from under the vine every few weeks, but they come back in a week or two. Do you have any advice on how to keep the weeds out? (e-mail reference)

A: The only thing I can recommend is Roundup. It should be applied carefully to the foliage on a day without wind. Use a paint brush to cover the terminal growth. This should eliminate your weeds. Generally, disturbing the soil encourages weed establishment, so once this crop dies out, cut them down and mulch the area around your vine to discourage future growth.

Q: Can spider plants thrive outside? I have a spot that gets partial sun in the morning.(e-mail reference)

A: Are you talking about permanently? It would not be a problem during the summer, but any frost episode would kill the plant.

Q: While shopping, I noticed several varieties of boxwood shrubs for sale. The shrubs are beautiful, so I would be interested in planting some in my front yard. The yard faces east and receives partial to full sun. However, I am unsure if they are hardy to North Dakota. The boxwood shrubs are common, green mountain and winter gem. The latter two especially caught my eye. I would hope that if they are being sold here that they would do well, but I don't want to go on the assumption that the retailer is looking out for me. Also, one other type of shrub that I saw was a crimson pygmy barberry. Any input on that one? I prefer the boxwood, but would consider the barberry in addition or instead. Any information you could provide would be much appreciated. Thank you in advance for your reply! (Bismarck, N.D.)

A: Glad you wrote to me before spending your money. None of the boxwoods are hardy to our state. The crimson barberry is not much better. It will survive our winters, but it will not look good. You are better off making plant purchases from a local entrepreneur who knows what grows in our unpredictable, capricious environment.

Q: I was given a little cactus with clawlike spines for Christmas by my boyfriend. I love the plant, but I noticed it was leaning a little to one side. Thinking it was sun deficient on one side, I turned it around to catch the light on the other side. While doing that, I noticed some white, fluffy substance around the base. It has since become limp and looks unhealthy. I only watered it when it was dry, but have I overdone it? I'm very worried because I asked for the plant. Is there anything else I can do? (e-mail reference)

A: There is a very good chance the plant will expire because of the slow rot taking place. If you can, carefully cut the base back to where it is free of decay. Allow the cutting to lie on its side for a full day before placing it back in a cactus media. When you water, do so with a very frugal touch. Don't give it a good soaking like you would other houseplants. If you think it needs water, wait another day or two. Keeping it in as much direct sunlight as possible also will benefit the plant.

Q: I have a large, old birch tree that sits in the corner of my front yard and provides shadow for the sidewalk running past my house. Shade is important because it gets quite hot in the summer. A few years ago, the top branches began to die and limbs would break and drop into my yard. Finally, the entire top of the main trunk died. I discovered a soccer ball-sized hole in the trunk about 20 feet from the ground. It was a home for animals. I thought it was a hazard, so I took out the top part of the tree. When I cut into the trunk below the hole, water gushed out and ran down the side of the tree. I had to stop cutting until it drained. This reduced the trunk to about 15 feet in height. The major part of the tree is now gone. All that is left are two large branches that grew from the main trunk. The branches still provide shade to the sidewalk. Will the major trimming I did keep the tree alive for a few more years or am I just engaging in wishful thinking? (e-mail reference)

A: Go for a replacement tree. I can't imagine this tree contributing anything aesthetic to your property. It may live for a few more years or it may not. It definitely will not be the graceful beauty it once was.

Q: We own a large plot of land about 30 miles southwest of Minneapolis. We are looking at planting a large row of Black Hills spruce trees as a privacy line. We expect to plant about 25 to 30 trees. We want to know how far apart to plant them. If we plant them about 9 to 10 feet apart, we are thinking that they will become a very thick row of trees within five or so years. Should we be concerned about overcrowding these trees at 10 feet apart? What about compromising the root system or making them more susceptible to disease? Any guidance or advice you could give us would be greatly appreciated! (e-mail reference)

A: Any time any biological entity, such as trees or animals, are crowded together, the chances for disease development go up a notch or two. However, many such plantings have been carried out with more successes than failures. At the density you are contemplating, you should have a solid wall of evergreens in about five years. The only problem is that you will not have nice, individual Christmas trees to cut and bring inside should you ever decide that is something you want, unless you like misshapen trees.

Q: We have a ficus tree that has been healthy and growing well for more than a year. It is an indoor plant that is located near a somewhat east-facing window. We put in a 1.5 spike of Miracle-Gro fertilizer into the pot about a month ago. During the last few days, many of the leaves have started turning a mottled or spotted yellow and then dropping off a day or two later. The leaves are falling off on the portion of the tree facing away from the window. We turn the tree every few months. (e-mail reference)

A: The fertilizer spike is unnecessary. I don't know what is causing the problem you describe, but I would suspect that it has something to do with a reaction from the plant to the fertilizer spike.

Q: I have a question about a thundercloud plum tree. I live in North Carolina, but nobody here seems to have a clue what is going on with my tree. We planted the tree about two years ago. It is growing very well and seems to be healthy. However, all of the other thunderclouds in the area keep their dark purple leaves all season. Ours turns dark green with burgundy veins. It is very strange. It also seems to be bearing tiny fruit, which I’ve never seen on other trees. Any idea what might be wrong with it? (e-mail reference)

A: It sounds like you might have been sold a thunderchild flowering crab by mistake.

Q: I have an apricot tree in my backyard, but don't know the variety. Each spring, it has bloomed and produced fruit for the 13 years I’ve lived here. This year, the tree had buds, but they did not bloom and seem to have dried up. Can you tell me if the tree is still viable or should it be removed? (Chicago, Ill.)

A: If all the buds are dried and the tissue under the bark is no longer green, then the tree probably is dead. If the buds have been nipped by frost, there is a chance the tree will releaf. Wait a couple of weeks before making a decision to remove the tree.

Q: I have three Christmas cactus plants lined up in front of a picture window. The problem is tiny ants. I just found many of them marching back and forth between the two end plants, but not bothering with the one in the middle. They are up and down the sides of the pots and the dishes at the bottom of the pots are infested. I can't seem to get rid of them. What should I do? (e-mail reference)

A: Ants easily are controlled with soapy water and a little garlic juice added. You can spray it directly on the ants and the path they follow. It will be toxic to the ants, but not to you or the plants. Ants are known for their high level of efficiency and industry. You might investigate the source of their activity and interest because it could be a harbinger of other developing problems.

Q: I have access to horse manure in a barn that hasn`t been cleaned for a couple of years. There is no straw in the manure. It is compacted with new stuff on top. Would the manure be good for my vegetable and flower gardens? I could scrape off the new stuff and just use the old manure. I know fresh manure isn`t good for a garden. I just don`t know if this is aged enough to be good fertilizer. (e-mail reference)

A: I don't know how good it will be for the garden, but it shouldn't hurt it at all if you use the old stuff. Be sure to mix it in the soil completely.

Q: I purchased a beautiful new jade yesterday. It has three main branches and is absolutely gorgeous. I have never owned a jade plant before. My first reaction is to repot it because it is in a plastic pot. However, that can't be a bad thing because it is doing so well. The plant has a few drooping ends, which makes me feel like it needs a larger pot. My second concern is where to put the plant in my home. I have been reading your Web site and it appears that jade plants are temperamental to sudden movement. I have a lot of indirect light in all my rooms. I have the option to give it direct morning or direct afternoon and evening light; however, all my windows are ultraviolet protected. Can you help me? (e-mail reference)

A: The closer you can come to aping the environment it was in when you purchased the plant, the better it will do in your home. Most jade plants suffer from too little light, so go with a higher light location rather than a lower one. As you read on my Web site, if you think it needs water, wait one more day. Also, fertilize at half the levels you read on the bottle or package of fertilizer. Do so only when the plant is starting to show active growth. Leave the pot alone because it seems like a lot of problems kick in after repotting. As long as the plant looks OK, don't worry about repotting.

Q: I moved into a property in France that has a mature, fruiting orchard. Some of the trees are a European breed of linden. All the trees are diseased, but the most puzzling problem is on the linden tree. It has started to develop red, spikelike protrusions on the top of the leaves and cluster in groups. I have contacted several people to find out how to treat the problem, but without luck. I am hoping you may be able to shed some light on my tree’s disease. (e-mail reference)

A: This is extra cellular growth resulting from the feeding of eriophyid mites. The mites produce what is known as finger or nail gall growth. As bad as it looks, the galls are harmless to the tree. There is no action that needs to be taken at this time.

Q: I live in New Jersey. My lilacs are blooming and are gorgeous! I have the nice purple plants with the edges of each tiny petal trimmed in white. I am guessing these are lace lilacs. I also have the plain, dark purple type that seem to die much quicker once they are cut and in a vase. I don't know why that happens. I searched to find the best information on lilacs, so that is how I found your column. I am enjoying my lilacs, but I am a bit confused, so forgive my ignorance. Bearing in mind that next year’s blooms are based on this year’s growth, where should I cut off the blooms? I guess I am unclear as to what specifically the bud is. Does that refer to the bloom? Where do I cut to maximize growth for next year and encourage the shrub to spread outward? (e-mail reference)

A: After you harvest lilac flowers, get them into a bucket of water immediately. To keep the blooms around longer, visit a florist to get bloom extender to add to the water. When you harvest your lilac flowers, you also probably are taking some of the leaves just below the flowers. That is where you want to cut your lilacs back if you want to prune them at all. As you know, if you do nothing, they will bloom anyway. The problem comes when the homeowner gets antsy to do some late-summer or fall pruning. That's when the blooms for the next year are removed.

NDSU Agriculture Communication

Source:Ron Smith, (701) 231-8161,
Editor:Rich Mattern, (701) 231-6136,
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Prairie Fare: Prairie Fare: Enjoy Lounging Outdoors With a Refreshing Beverage  (2019-06-13)  If plain water is kind of boring, try infusing it with fruit and/or herbs.  FULL STORY
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