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Ron Smith answer's readers questions about the world of plants, trees and gardens.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I found your Web site during my quest for the ultimate answer to quack grass control. Two years ago, I built a new clinic on six acres of undeveloped land next to a creek. Fill dirt had been hauled in, but about four acres of it was virgin land. After the site work was done and the building completed, I planted about an acre to buffalo grass and about as much to a prairie grass/wildflower mixture. I had a severe problem in the buffalo grass with crab and quack grass, as well as the normal broadleaf weeds. Last year a pre-emergent pretty well took care of the crab grass and 2,4-D the broadleafs, but the quack grass was a bad esthetic and control problem. As you know, buffalo grass is a low, slow-growing grass, which is my reason for planting it. I cut it down 2 inches and waited a few weeks. By then, the quack grass was 6 to 8 inches tall. I glued four kitchen sponges about 4 inches high to the front of a fertilizer drop spreader. I let the glue set and then mixed a fairly strong Roundup solution and put it in a hand sprayer. I saturated the sponges until they dripped. I let the excess drip off and went over the whole area. The sponges coated the top of the quackgrass leaves, but not the buffalo grass. I saturated the sponges after each pass. It put a definite hurt on the quack grass. I did it two times because I missed some areas the first time. I intend to build a contraption this year that is adjustable in height so I can do the wildflowers that are infested with mare’s-tail, a very nasty weed. I sickle cut it last fall and had a high school kid pick up the material and burn it. Of course, I can't use a broadleaf killer on the area because of the flowers. I don't know if this might work on cool-season turf grasses because my blue grass sod did not have nearly the problems the other areas had. I was able to spot treat, pull or gouge or the mare’s-tail out. (e-mail reference)

A: Thank you for the educational report on controlling quack grass! In slow-establishing warm-season grasses, such as buffalo grass, the cool-season quack grass can get off to a sprinter's start before the buffalo grass even wakes up! Mare’s-tail is renowned for many things. It is the first recorded glyphosate-resistant weed. Mare’s-tail has 250,000 seeds per plant that easily blow from field to field. It has the ability to form natural hybrids with other members of the genus Conyza. It also confounds weed control efforts because it has a variable germination time. Classed as a winter annual, it usually germinates in the fall, but will do so any time the urge hits!

Q: Now that snow is melting, we have discovered severe damage to our small apple trees and woody shrubs (such as bridal wreath type). At the base, many of the stems/trunks have been eaten away. What can we do to help save the plants? I am especially concerned about the young apple trees. Many thanks. (e-mail reference)

A: The young trees are goners. The shrubs should be cut back to the ground so new growth can emerge from the base (crown) of the plant. Sorry to deliver bad news, but you have a lot of company!

Q: My hoya plants have been under a fluorescent light for a long time. The plants are growing in perlite and the planter is made of clear plastic. The plants are doing well and growing new leaves and roots. However, the leaves are turning red. I guess I need to transplant them into soil, but what type of soil should I use? Should I keep the plants moist all the time or let them dry out between waterings? Can I use the plastic planter? (e-mail reference)

A: The red foliage is an indication of a nutrient deficiency. Transplant the hoya plants into any good potting soil that is sterilized or pasteurized. Do not keep the plants wet all the time. Cover the plants with a plastic bag (leave the bag open) for a week or two, but randomly take it off for a few hours each day to toughen the plants. As you get to the end of the second week, try leaving the bag off for a half-day. Then try leaving the bag off during the day, but covering the plants at night. You will reach a point where you can leave the bag off, but monitor the plants to make sure they don’t start to wilt, even though you are giving the plants sufficient moisture. If the plants do start to wilt, start over with the plastic bag.

Q: I have two ponytail palms that appear to be very root-bound. I have had these two ponytail palms for close to 20 years. They are planted in faux terra cotta pots that are 22 inches in diameter and 17 inches in depth. I feel the palms need to be repotted because they have been in these pots more than five years. You can see the roots are very dense at the top of the soil. One of the palms has its crown growing to the side as if it has been bent. The palms are kept outside and get good light. Both plants are about 5 feet tall. What should I do? (e-mail reference)

A: They need to be repotted. However, unless you are an Olympic weight lifter, you'd better get some help. Ponytail palms are among the most long-lived houseplants that someone can grow and, if not overwatered during the winter months, are a piece of cake to care for.

Q: Thank you for all the great ideas that you provide in the weekly Farm Forum. I want to share with you an amaryllis story. I have found that, with minimal care, you can get them to bloom for many years. My mother-in-law gave me a bulb at Thanksgiving time in 1997. It bloomed for the first time that winter. The instructions that came with the bulb said to let the stem shrink on its own after blooming and then remove the flower stem at the base. Next, set the plant outside in a place protected from the wind after all the danger of frost is gone. In the fall, but before the first frost, bring it in and put it in a dark place, such as a closet or even a brown paper bag. Do not water it and let the leaves die back. After it has rested for about six weeks or it begins to sprout new leaves, bring it out again and start to water sparingly at first to let the leaves develop strength. I haven’t followed the instructions exactly, but I must be doing something right because the amaryllis has bloomed every year despite giving it very little attention. One year it even produced a double stem of flowers. Right now the flower head is peeking out from the bulb next to two leaves that are 30 inches long. When done blooming, I expect there will be about 10 new leaves that will come out because it happens every year. If I counted right, this should be the 11th time that we have had flowers from this bulb. Maybe it's the love that I have for the wonderful lady who gave it to me or maybe it is the Miracle-Gro. Perhaps it is a combination of both that is supplying the success. I don't know. It will be interesting to see just how many years this bulb will bloom for me. (e-mail reference)

A: Thank you for your very interesting and successful story. There are a lot of success stories out there, as well as many frustrations with this bulb. I'm always glad to hear good news when it is available!

Q: I need help with my dieffenbachia because it has taken a turn for the worse. It was beautiful, big and lush. I was quite proud of it. However, one morning we discovered it bent over at the stock just above the dirt line, but was not broken. There also is a smaller shoot that did the same thing. I was thinking it was top-heavy and loose from the stake, but restaking didn't help. Can I trim it? I've never pruned an indoor plant other than taking off dead or yellow leaves. (e-mail reference)

A: My suggestion is radical, but has worked in the past for me. Cut the plant off at the base, but leave a 4- to 6-inch stub. You can cut the stalk you took off into 6-inch pieces and propagate them or throw the stalk away. See if the stalk in the pot sends out a shoot or two in a few weeks. If that happens, get an oscillating fan and direct it at the plant as it grows. This will build a stronger stem that will be able to support the increasing weight as it grows. You also might add a plant light or two to get the plant more energy to build stronger, denser tissue. If the stem is rotten, it won’t work and the plant will be beyond help.

Q: I am located in Tennessee. I just planted a weeping willow approximately 20 feet from the corner of my house. Is this too close or is the distance acceptable? (e-mail reference)

A: That distance is just fine. Unless your basement walls leak like a sieve, you have nothing to worry about.

Q: I have small flies that are in my house plants. How can I get rid of these flies? They seem to be all over the house. I have about 50 house plants, so to change the soil would be a major undertaking. (e-mail reference)

A: The flies eventually will die. In the meantime, you can get some yellow sticky cards or tape to reduce their numbers quickly. Hang them where the fly concentrations appear to be highest.

Q: I live in south-central South Dakota. How soon can I prune my roses? Do you prune during the dormant season the same as shrubs? (e-mail reference)

A: That's correct. Prune the roses at the same time you would other dormant deciduous plants such as crabapples.

Q: I am going to plant six emerald arborvitaes this spring, so I could use some tips on how to plant them. The soil is hard, but manageable. Should a particle or spray fertilizer be used after planting? What kind of planting fertilizer mixture should I use? What is the call on using burlap for the winter? Thanks for any help. (Pennsylvania)

A: Work the soil up before planting. Do it all along the row where the plants are going to be installed. Add some sphagnum peat moss and mix as thoroughly as possible throughout the entire site, not just the planting holes. Make sure the trees are planted at the proper depth. Water well at planting time and about once a week to 10 days thereafter for the balance of the summer unless you get some heavy rain. No fertilizer is needed or suggested. Burlap should not be needed for the winter unless it will make you feel better to wrap or build a burlap shelter around the planting prior to winter's arrival. As the plants mature, they should not need winter protection.

Q: I have two spider plants that were very vigorous. I was on vacation this winter and did not water the plants for three weeks. Ever since, the newer leaves on both plants have had problems. They are pale, curly and very rough (almost like sandpaper). Do you know what could be wrong or how I might fix the problem? (e-mail reference)

A: The spider plants probably went into dormancy. The leaves that are affected will not change. If you follow your usual watering regimen, new growth will emerge. The new growth will have the normal characteristics of the species.

Q: I received potted tulips as a gift about a month ago. I have attempted to replant them in the pot they came in. However, I am concerned I may have made a few mistakes. There are six to eight bulbs with no space between them. Should I replant them in a larger pot and place them deeper into the soil? I live in an apartment, so I do not have an outdoor garden or yard. However, I have an outdoor patio where I can place a pot to get sunlight. Should I be removing all of the pre-existing roots and planting the bulbs in fresh soil? I have cut off all of the dead foliage. However, I left about 3 inches from the tip of the bulb. Do I remove what seems to be a dead casing around each bulb? I am entirely new at this, so all the advice you can give is appreciated. (e-mail reference)

A: These are forced bulbs by the grower. The bulbs are given a chilling treatment to get them to break dormancy and bloom. Unless you live in the north, where the bulbs can be replanted outdoors this spring or summer to go through a winter season with below- freezing temps, these bulbs are not going to produce anything further for you. Unfortunately, I suggest you dump them.

Q: We have a plum tree in our backyard. We love the shade, but despise the plums because they taste very sour. Is there something we can do to the tree to prevent it from bearing fruit? I will take any suggestion you have. (e-mail reference)

A: If the tree is big enough to provide lovable shade, then you need to hire a professional service to spray the tree with a hormone-type material, such as NAA or IBA, at the right time. Depending on your motivation, you can help the thinning process by doing some hand thinning when the fruit is pea or marble sized. If the tree is small enough for you to reach the entire canopy with a backpack sprayer, then you might be able to do this yourself. Keep in mind that timing is everything in spraying any material to control fruit set. It will never be 100 percent successful because the flowers are never at the same stage of vulnerability at any given point in time. Some are perfect, some too immature and some overly mature. If the cost isn't prohibitive, a couple of sprays about three to seven days apart would give you the most complete control.

Q: I just read through some of your material while searching for an answer to my problem. We live in Minneapolis and have a maple tree in our front yard. I don't remember the exact variety, but it had beautiful red/orange fall color until the last two or three years. During the last few years, it has developed very weak growth on the east side and some branches are dying. The west side of the tree seems to be OK in comparison, but not as vibrant as it once was. I've been trying to diagnosis this myself without success and the nurseries haven't helped. We have a line of black walnut trees in the backyard. I thought that if the walnut trees damage the maple tree, it would've happened early on. I do have some daylilies planted at the base of the maple tree. Could the daylilies be girdling the roots? Is it worth the expense to call an arborist? Should we replace the tree? We really love the tree and were looking forward to its long, healthy life. (e-mail reference)

A: All I can do is give you some guesses. It could be a canker developing on the weak side or bark beetles or borers working on the cambium. It also could be a vascular wilt fungus getting started. It probably would be better to simply remove the tree, but try to get a diagnosis from the University of Minnesota Plant Diagnostic Clinic as to what the problem is. That way, you will know whether it is safe to replant the same species.

NDSU Agriculture Communication

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