December 25, 2003

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: I have large pine trees in the front yard. I raked up the dry needles. Can I put them on the garden or does the sap harm plants? (E-mail reference)

A: Pine needles will do an excellent job of physically conditioning the soil, so go for it!

Q: I was given two 15-year-old ficus plants that have done well in front of a large bay window. Because of their location relative to the window, they have bowed significantly. I am currently using ropes to hold the trees straight but one will not stand upright without the pot lifting from the floor. Is there anything I can do to the trunk such as wrap it with damp towels to aide in the straightening? Would an indoor plant lamp help if placed on the opposite side of the bow? (E-mail reference)

A: You can turn the tree 180 degrees on a regular basis to help keep the growth straight or you can place a couple of high intensity plant lights on the opposite side to cause the plant to grow back to a more upright position. The response will be limited because the tree is mature and has developed a hardened xylem. Most of the response will come from new growth that will come over time. Be patient.

Q: I am enclosing a sample of some evergreen shrubs that are in the front of our house. They are on the east side, are about 4 feet tall and need to be trimmed so they don't block the picture window. Can you tell me the name of the shrub, and the proper way and time of year to trim them? (Tyler, Minn.)

A: Your sample was that of an arborvitae but which one is impossible to tell. These plants are pruned in early spring, prior to the start of new growth. When you prune, do not leave a bare branch. Always leave some green foliage right below the cuts. That is where the new growth will be generated. To encourage dense growth, I would suggest giving the plants a shot of fertilizer like Miracle Gro or something similar.

Q: My variegated dogwoods were attacked in late summer by something. I’ve enclosed a sample. What preventative measures should I take next season? (Carrington, N.D.)

A: It looks like a combination of heat stress, salt toxicity and some kind of leaf spot disease. Clean up fallen leaves and spray the shrub with lime sulfur next spring before leaf out. Don't fertilize but do water on a regular basis through the summer.

Q: Would you please send me information on a mail order source for both ornamental rhubarb and Sorrel plants? (Lake Bronson, Minn.)

A: As much as I tried, I could not find any sources for you! Perhaps one of our readers will know of a source and pass it on to me. Sorry!

Q: I have a huge dieffenbachia that is absolutely beautiful with leaves in the middle and the top. The leaves in the middle are wilting and dying. The top leaves still looking fine but I am very concerned. It was in a pot too small for it and the weight of the plant was almost toppling it. I have transplanted it using good quality potting soil. It is in the master bedroom in front of a window facing east so I am thinking maybe it is a bit drafty. I have just given it a good watering (it has proper drainage). Hopefully that will do the trick. I transplanted it about a month or so ago and so far it has lost two middle leaves with another two about to fall. (E-mail reference)

A: Your dieffenbachia needs a little help. I have some suggestions but sit down before reading on because this is going to sound drastic. Cut the plant back to about a 4-inch stub. Take the cane that you cut off and cut into 4-inch sections and lay them on their side in a flat of damp sphagnum peat moss (soak it completely first, then wring as much water out of it as possible). Be sure both ends are barely covered with the damp sphagnum. Keep it moist and in about six weeks you should see some leaves developing from the top of the stem and roots developing on the bottom. Wait another two to three weeks for the embryonic tissue to develop further, then remove and pot. You should have at least a half dozen successes using this method. You could also do air layering. If you are interested in doing that I can send you our publication, "Home Propagation Techniques."

Q: I have a kalanchoe plant that I keep in a south window. It bloomed last year but I can see it's not going to bloom this year. I see tiny black spots on the leaves and the ends of some leaves are drying up. What is wrong? (Onaka, S.D.)

A: Based on the symptoms you described, it could be too much water, poor drainage or over fertilization.

Q: I have a large-leaf plant but don’t know its name. Each leaf is the size of a small dinner plate. It has brownish spots on the upper part of the leaf. I'm guessing some type of blight. I’ve been misting but quit doing it to see if the plant gets better. It's large and in a small pot so I’ve repotted. Any other suggestions? (LaMoure, N.D.)

A: You did the right things so wait to see if things improve after awhile.

Do you have a gardening or houseplant question? Write to Hortiscope, Box 5051, NDSU Extension Service, Fargo, ND 58105 or e-mail to Ron Smith at ronsmith@ndsuext.nodak.edu. Note to e-mail correspondents: please identify your location (city and state) for most accurate recommendations.

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Source: Ron Smith, (701) 231-8161, ronsmith@ndsuext.nodak.edu
Editor: Rich Mattern, (701) 231-6136, richard.mattern@ndsu.nodak.edu