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

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I am trying to gather some information on planting a plum tree. This past summer, I took two healthy plum shoots from an heirloom plum tree on my uncle's farm in West Virginia. I took them home with me to Tennessee and planted them in pots using a mixture of Miracle-Gro, manure and compost. What is the proper way to plant them outside? The temps here are in the mid-40s to upper 50s. Do I need to put mulch around the top after I plant them in the ground? Your guidance would be appreciated. I would like to have some plums in a few years. Thank you. (email reference)

A: Congratulations getting the plum trees started. Get them planted in the ground at your earliest convenience. Because the soil doesn’t freeze in Tennessee, the roots of the plants will remain active through a good part of the winter months and will get the trees prepped for a good shot of growth next spring. Not knowing what the extreme lows are in your part of the country, I encourage you to use a 2-inch-thick organic mulch of bark or peat moss. If you don’t have any measurable precipitation for a couple of weeks or so, give them a good shot of water.

Q: I have two beautiful red prince weigela bushes. I’ve read a lot about the bushes, but can’t find anything on how to prepare the bushes for winter. They are in a protected area by the house but get plenty of snow during the winter. Should I cut the branches down to so many inches off the ground, level with the ground or just leave them alone? Love your column. (Valley City, N.D.)

A: Cut the weigela bushes back to the ground. They will shoot new growth for you next spring. Allow the snow to accumulate because it is one of nature’s best insulators. Thank you for being a devoted reader of the column.

Q: I was reading your responses about oak trees, but I still have a question. I live on Cape Cod, Mass. We have many scrub white and red oaks. During the summer, my screens and window sills are filled with what appears to be dark dirt. I wipe away the dirt almost every other day. I do not have this problem now that it is fall. I feel this dirt is from the many tree (perhaps 30) in the yard. We have a grass lawn and a seashell driveway, so there is no dirt coming from anywhere else. Any ideas what this mess is and how we can eliminate the problem? Thank you so much for your time. (email reference)

A: I have no idea. This is a problem that needs to be looked at locally. Go to to find your local county Extension agent.

Q: I have two questions about a climbing hydrangea that is about 10 years old. I have it growing on a trellis that is a few inches away from a brick chimney, so it is climbing on the brick. It really attaches itself to the brick and is difficult to pull off. Can it damage the brick or mortar? I pulled some off today and it leaves little roots. Also, it never has bloomed. Is there anything special I should be doing to get it to bloom? Thanks for the information. (email reference)

A: Roots from a climbing hydrangea, Virginia creeper or English ivy will damage the mortar and brick. If you can leave it up, the damage will be minimal. However, like anything else that goes up, it eventually will come down, and that's when the substantial damage has a chance of occurring. As to the lack of flowering, it could be tied to our low winter temperatures. The flower buds are more vulnerable to low-temperature damage than the foliar buds. As far as a climbing vine goes, this is the champion of them all because of its unique leaf character and branching habit as it climbs. If it can be used on a structure that isn't going to be impacted by the clinging roots, such as an old post, fence or petrified tree, it is a fantastic choice.

Q: Our tree split apart, so we had to cut it down. Now we have bushy plants popping up. How do we get rid of them? (email reference)

A: You can use Roundup or a broadleaf weed killer such as Trimec. It all depends on where the suckers are coming up. If the plants are coming up in your lawn, then it should be Trimec so you don’t kill the grass. Follow the label directions to eliminate broadleaf weeds. If they are coming up in a spot that has no other vegetation you deem important, then use Roundup because it is a nonselective product that will kill anything with green foliage. In either case, you might have to do another application next year.

Q: Is there a rule of thumb on the temperature needed for dormant seeding? I thought I read somewhere that the temperature needs to be at 40 degrees for a certain number of days. Thought I’d see what you had to say on this. (email reference)

A: Dormant seeding is a combination of shortening day length and lower average temperatures. With the shorter days, little to no germination of Kentucky bluegrass is going to take place, especially when coupled with our cooler weather. It is safe to dormant seed now or anytime before freeze-up. A higher seeding rate is needed for dormant seeding because of the higher attrition rate. The seeds will go through a priming process, which will get the seeds ready to shoot out of the ground when we get consistently warm spring weather and lengthening daylight.

Q: I recently moved to Florida and received a jade plant as a housewarming gift. I think it’s one of the most unique and cool plants I've ever seen. Because it is a hanging plant, I put it outside so it could get some sun. However, it rained for several days, so the jade was soaked. It took about two weeks for the plant to dry, but the soil still is moist to the touch. The leaves are dying and the plant looks like a lost cause. My biggest concern is the stems going into the soil. The stems are brown and dry. Can it come back from this problem? Is there anything I can do to help the plant? I'm new to this type of plant, so I'm at a loss about what to do. (email reference)

A: You are right that jade is a cool plant. Unfortunately, from your description of what yours went through, it is dead. I encourage you to not give up on this adventure of raising a jade plant because you can have success. Go to for all the information you need to raise a jade plant. Basically, jade plants are easy to grow. However, like most living organisms, they typically don’t adapt well to sudden changes. Jade plants thrive on following a good routine. Jade plants need consistent, moderate light intensity and duration. They need consistent watering, but drying gradually in winter. The plants need to be in containers that drain well. Fertilize when new growth is noted in the spring. Jade plants need to be monitored for spider mites during the winter because of the dry air. You also need to check for scale and other sucking insects. Be sure not to overwater the plants.

Q: Someone gave me a peace lily with instructions not to overwater or underwater the plant. I placed the plant away from heat, drafts or sunlight. I water the plant when the leaves begin to droop, but only sparingly. However, the leaves are turning brown and shriveling. I cut the browning or brown leaves off, so now the plant is beginning to look sparse. I have tried to diagnose this problem and cure it but have had no success. Would you be able to tell me what might be causing this problem and what I can do to correct it? A friend suggested that I repot and divide the plant. However, I would like a second opinion. If dividing is the answer, what kind of soil and pot should I use? Thank you for any assistance you can give me in saving this gift. I have lots of other varieties of plants, but this is the only one giving me grief at this time. (email reference)

A: You were given incorrect information on the water requirements of this plant. Peace lily plants are one of the few houseplants that thrive on plenty of water. They are tropical in origin, so they are genetically hardwired to have continuously moist soil. The big ringer in this is to be sure the soil and containers are free-draining. If the water pours through the soil and sits in the saucer, empty the saucer within 30 minutes of watering. Fertilization also is a tight requirement. Peace lilies should get a weekly dose of diluted fertilizer. Use about 50 percent of the recommended rate. The fertilizer also should contain micronutrients. During the winter months, back off somewhat on the watering and reduce the fertilizing to once every six to eight weeks.

Q: You seem to be the resident Christmas cactus expert. I have a Christmas cactus that I unknowingly overwatered. It sat in standing water for several weeks before I noticed it. I drained the water thinking the plant might come back, but it hasn't made a recovery. All the foliage is wilted, but the soil is dry. Should I repot it or is it a lost cause? I'm sure you're very busy, so thank you for your time. (email reference)

A: Christmas cactus is a tropical forest plant, but it doesn’t sit in accumulated water in the forest. The roots very likely have rotted away, so the chances that the plant will recover are remote. I would counsel you to dump the plant and learn from this that you need to keep the plant hydrated but never sitting in standing water. Sorry!

Q: I have some farmstead trees that were sprayed with a high dose of glyphosate. The South Dakota Department of Agriculture investigator found varying levels of glyphosate herbicide residue in the grove and by my house. One part of my grove was sprayed so severely that it killed the established grass under the trees. The trees are approximately 30 years old. How can I evaluate short- and long-term damage? The trees are Russian olive, ash and honeysuckle. (email reference)

A: I’m sorry to hear of the damage caused by this careless act. You need to get a professional to objectively assess the value of your loss. Your best contact is John Ball at South Dakota State University. He is an International Society of Arboriculture certified arborist. He can do the assessment or recommend someone who can give you an opinion that would be valid in a legal hearing. Ball can be reached at (605) 688-4713.

Q: I took the Master Gardener class 10 years ago and keep active at gardening by helping others. Someone brought me a tomato that was very interesting. The other tomatoes on the plant are fine. This tomato has a scablike skin on one side. The man who brought it in (doctor) thought it looked like a tumor. However, the skin looks like it has grown over the tumor. It almost looks like the tomato is healing a wound, so that's why it is so weird. Thanks for your help. (email reference)

A: It could be a bacterial disease, although it doesn’t quite fit with your description. I have never heard of a scab being grown over, but that doesn’t mean it can’t happen. As long as I’ve been in the horticulture profession, I’m still learning things. The only other possibility would be a physical wound caused by the weather, insects or birds. The wound may have occurred early enough in the season that the fruit had the ability to compartmentalize it by forming a tumor-type covering over the wound. However, these are just educated guesses.

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 – Nov. 8, 2011

Source:Ron Smith, (701) 231-7971,
Editor:Rich Mattern, (701) 231-6136,
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