November 13, 2003

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: Every year I collect and burn at least a cubic yard of black walnut leaves. I understand that the trees or leaves are allelopathic to certain plants. Can I use the composted leaves in my garden? (Dent, Minn.)

A: I don't know if the allelopathic character would be carried over during the composting process. You might want to try a little around some tomatoes or peppers to see what effect it might have. I wouldn't suggest placing it wholesale on the garden until you experiment with it a little first.

Q: We have problems with our blue and black hills spruce. We have been planting trees for about five years and most were doing great until two years ago. The trees that are not looking good are in various parts of the yard. The first tree that died was a blue spruce that we transplanted with a tree spade. The tree did well the first year after moving, but the second year it developed brown needles mostly on the bottom. I cut off all the dead branches back to the trunk thinking I would try to save the tree. The next spring more branches needed to be trimmed so we took it down. This spring other blue spruces in the yard looked great until March or April when they began to lose their new growth. The largest was planted about 5 years earlier and couldn't have looked healthier in March. My husband fertilized with a slow release fertilizer in March and then it rained a lot. About three weeks later green needles began to fall. Some entire branches lost their needles. The branches that did not loose their needles did fine throughout the season. We had our ph tested and it is neutral so I put miracid on them. We have about 15 Black Hills spruce in our yard as well which also do not look very good. We watered and mulched the trees during the drought this year. The trees still seem to be developing brown branches that die all the way back to the trunk. We know that some of the trees had gall aphid disease so we sprayed and picked off the galls. All of the trees were bought and planted by a very reputable nursery in town. Our neighbors have many black hills spruce that look great. We do not know what we are doing wrong. (Rochester, Minn.)

A: I would go back to the nursery and ask for an opinion. It could be any number of things that are causing the problem, environmental, soil toxicity, insects, diseases or a combination.

Q: I have a beautiful Boston fern that has been in my family for years. It was my mother-in-law’s pride and joy. She has now passed and I want to keep it healthy. It is doing well, except that some of the fronds are turning yellow in the middle and dying. Am I giving it too much water or not enough? It is in an east window and seems to love it there. That is where it has always been. (E-mail reference)

A: Occasional die off of a leaf or two is not uncommon. Keep it misted with distilled water and in general don't worry about overwatering it. Misting is quite critical to get the plant through the winter months when the central heating systems are in full use and drying the air. Certainly don't move the plant.

Q: I have a crown of thorns that was passed down to me from my parents. It is 27 years old and very large. I have never done much to it other than water it and take it outside during the summer. It blooms all year long but now after bringing it inside this year, some branches are turning spongy and the leaves are turning yellow and falling off on some branches. I do not see any mites or fungus. I used an insect soap spray but that is not helping. (E-mail reference)

A: Back off on the watering and allow the soil to dry between watering cycles. Also make sure it is gets bright, but indirect, light.

Q: Are you supposed to wait until the ground freezes before you mound roses with dirt? It is hard to find dirt that is not frozen if you wait that long. (E-mail reference)

A: I suggest getting potting soil that has been sterilized or pasteurized to place over your roses. That way you don't have to worry about trying to move any frozen soil. The clean soil will be free of pathogens that might get started if you are not gung ho enough about removing it in time next spring.

Q: What kind of soil should I use for a bonsai tree? (E-mail reference)

A: A soil and container that have good drainage characteristics.

Q: Recently I noticed a white/very light green, powdery mold in the soil of my plants. The plants themselves seem to be fine. The only problem I see is on the jade plant. A few leaves at the base have a few white spots. I've looked all over the Internet for a way to rid the plants of the mold and now my head is spinning. (E-mail reference)

A: Go to the local garden supply store and look for Schultz's Neem Oil. It is sold as Fungicide 3, which is a product that has multiple uses. It may help correct the problem. In the meantime, set up a fan to blow a gentle breeze at the lower portion of the plant and top of the pot. That should help keep the problem in check.

Q: I have a Christmas cactus that is approximately 20 years old. It stopped blooming for various reasons. It is in a ceramic pot that has it's own base for good drainage. However, along the top and bottom there is a large amount of salt build up. At least I think it’s salt. It is powdery and almost rust like. It is on the pot but not the plant. I wash the pot frequently but the salt continues to come back. How can I stop this build up of salt? I believe it’s the reason it stopped blooming. Would a plastic pot be better? (E-mail reference)

A: Salt buildup comes from the water source and is not uncommon in ceramic or plastic pots. Occasionally water the plant with distilled water to flush the salts out of the rootzone. This presupposes that the pot is freely draining and that the owner will dump the excess water flowing into the saucer within 30 minutes after watering. You might be watering with soft water, which is high in sodium salts, or your water may be naturally high in soluble salts. If you think a plastic pot would work better for you, give it a try.

Q: I have a large jade plant that is perhaps 15-years-old. It was beautiful and doing very well but in the last 6 months some branches started falling off. They look soft and wrinkly. I can't see any bugs and I haven't had it outside for two years. It still has new growth, even though some of the branches look like they have soft rot. I water it every two weeks as a general rule, though sometimes weekly. I gave it more new dirt a few months ago and I usually fertilize it at least once a month. (E-mail reference)

A: I would suggest taking cuttings, stem or leaf, from the healthy part of the plant in case this one dies. It sounds like a soft tissue rot is taking over. Once it starts, it is almost impossible to keep it from spreading.

Q: I am in serious need of help. My jade plant, which I love dearly and have owned for just a few short months, has collapsed on me. Its dew is seeping from creases under the leaves and the whole plant is fairly limp. I don’t know what could cause this sudden change and am extremely worried and saddened by this. (E-mail reference)

A: Very likely the jade won’t survive. Sorry! I encourage you to try another one, perhaps smaller this time. And be sure to get care instructions from the place of sale. Jade needs strong light, with some direct light for 2 to 4 hours a day. Jade has modest water requirements, more than a cactus but less than an African violet. It requires cool temperatures and should be kept away from direct drafts of hot or cold air. Most jade plants die because of overwatering in a low-light situation.

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