January 24, 2002

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: Do you have a suggestion on how to get rid of what looks like white mold (on the red blooms) of my indoor poinsettia plant? (E-mail reference)

A: The white mold is likely cottony cushion scale. It would be very unusual to have white mold on a poinsettia grown as a houseplant. The air in winter is simply too dry to have it develop.

Dip a cotton swab in rubbing alcohol and rub it over the spots you are calling white mold. If I am incorrect and you do have a low-grade fungus, it is probably powdery mildew. In either case--white mold or powdery mildew--you are better off dumping the plant than trying to correct either problem.

Q: I have had my peace lily plant for about a year and have repotted it once. It was in flower when I purchased it, but has not flowered since. The plant appears happy enough, but doesn't seem to grow very rapidly (E-mail reference)

A: I would say that you are probably a little impatient. If it hasn't flowered by the end of this spring, get back to me. They are a low-energy input plant, so it takes about a year for them to produce a flower, generally in the spring but sometimes in the fall, depending on their vigor.

Q: My Christmas cactus is wilting and has not bloomed this year. Any advice on caring for this type of plant and correcting the wilt problem would be greatly appreciated. (E-mail reference)

A: Wilting is not good for the Christmas cactus. I suggest trying to propagate it with some cuttings, selecting the firmest leaves you can find.

Q: I received a bonsai tree as a gift. I am confused about winter care. Most information on the Internet says to keep it outside over winter. I have a feeling they aren't talking about North Dakota. Any suggestions for winter care would be appreciated. (Minot, N.D.)

A: It must be an evergreen, and yes, you are right, they didn't have North Dakota in mind when they made that suggestion! I would store it in as cold (non-freezing) a room as possible where natural light can reach it. Watch out for dehydration, and if the temperature does go below freezing, make sure the root system and container is wrapped with some insulating cloth or other suitable material. The roots have a lower tolerance to low temperatures than do the stems.

Q: I have a question for you on my China Doll houseplant. I got this plant when it was about 6 inches tall, two years ago. It has grown to be probably about 6 feet tall. Within the last four to six months I've noticed it seems to be dropping so many of its leaves. I've checked them many times thinking it was spider mites, but it is not. I have not changed anything as far as caring for it, but the leaves turn yellow and fall off for no apparent reason. Any ideas as to why or suggestions as to what I can do to correct this problem? (Bismarck N.D.)

A: Something must have changed, whether or not you have changed your care technique for it. The plant could be root-bound, salts could be accumulating, forced air heat could be hitting the foliage, a draft from a door or nearby window could be causing defoliation. You obviously had to repot it in the past two years to have it go from a 6-inch to a 6-foot plant. Something has changed in the plant's environment. Weaker light? If you use fluorescent bulbs, their intensity decreases with age, mostly undetectable to the human eye but readily perceived by the plant, with the usual response being leaf drop to compensate for the lower light intensity.

Q: I have a spider plant that is growing well. My only problem is my cat keeps attacking the plant. She takes part of a leaf off. Also when it has the stem for new babies she either takes the stem or each baby plant. Can you tell me why she keeps doing this? Will it be harmful to her? (E-mail reference)

A: Don't feel like you're alone! My cats do the same thing every time we bring spider plants down to the sink to water them. My three cats are 11, 10, and 7 years old and it hasn't hurt them yet! Apparently something in the plant's structure or chemical makeup is attractive to them.

Q: I currently have a pine tree located in the center of a square area of approximately 20 feet by 20 feet. Up until the night of Aug. 8, when the wind storm came through Grand Forks, this was a beautiful blue spruce tree of approximately 70 feet. While this towered over the house, we had become accustomed to the tree and could watch the birds in it from our dining room patio doors. In the storm we lost the top 45 feet or so which came down on top of the house causing some damage. We now have a pine tree that is topped at about 25 feet. Is there any hope for this tree or would it be best to get rid of it? If one were to get rid of it, what would you recommend to replace it with? If it were replaced, I would like something that would fit the space better and maybe not be as tall as the old tree, and since it is so close to the house it would need to be something that wouldn't damage the foundation with its root structure. I would appreciate your thoughts on what we might consider doing. (Grand Forks, N.D.)

A: There is no hope for the tree, spruce or pine, whichever it is. It may stay alive, but it will not be a complement to your home. I'll make some recommendations, both deciduous trees and evergreens. The deciduous tree I'd recommend is one of the many cultivars of the Amur Maple. There are at least three worth considering: Red Wing, Embers and Flame. All have beautiful red seed (aka samaras), attractive fall color, and don't grow out of scale to a home residence. I have one in my back yard, right next to the patio. We really enjoy it. Another one with interesting character, but not fall color, is the Stately Manor (a male form of) Kentucky coffeetree. The leaves are twice and sometimes thrice pinnately compound, giving a graceful appearance in summer, but the rugged bark and branching habit give it an entirely different character in winter. Finally, the Dakota Pinnacle birch is a white barked species that is borer resistant and is also compatible with residential settings without overpowering. The evergreens would be Black Hills spruce (Picea glauca var. densata), a much better adapted tree than the blue spruce; the Sentinel cultivar of the Scotch pine, or the Swiss Stone pine, a very beautiful five-needled pine. Of the three I tend to like the Scotch pine a little better because of the exfoliating red bark that develops as it matures, but the choice is yours. You won't go wrong with any of these selections.

Q: Can the lead paint on a pot kill the plant inside it? (E-mail reference)

A: No! Lead was used as pottery in ancient Roman and Greek cultures, and according to history, the plants did all right. At least Pliny, the Roman naturalist and writer, never wrote about the lead killing plants. However, if you have children in the residence it would be a good idea to dump the pot.

Q: Can you tell me what would cause white mold to start growing on top of the soil of my houseplants? Some of the plants' leaves are turning brown and falling. Any help will be appreciated. (E-mail reference)

A: If you are sure it is white mold, then it is due to overwatering and poor drainage, which is being further reflected in your leaf discoloration and defoliation. It could also be salt accumulation from the high salts in the irrigation water, which could be exacerbated in a poorly drained pot or soil mix. In either case, I suggest repotting and using containers that are free-draining. If your water is high in salts, dilute occasionally with distilled water.

Q: My daughters have given me sensitive plants on Mother’s Day for a couple of years. One grew very well into a 3-foot high bush. It bloomed and seemed to be doing very well. Then, all the leaves got brown on the end and started falling off and the plant eventually died. I've tried several times since to grow another one but they all seem to have the same problem. I'm still getting new branches and leaves, but soon after they come out, they dry and drop. The plant grows upward but with few leaves. I've tried different watering techniques and different locations in the house without much luck. Any ideas? (McLeod, N.D.)

A: The sensitive plant, or Mimosa pudica, is more of a horticultural houseplant novelty than something to seriously consider as a permanent resident in the home. It requires as much natural sunlight or artificial lighting as you can provide for it. Because of the spindly growth, it should be pinched continuously to encourage bushy, compact growth, and possibly flowers. In the tropics this is a widespread weed that I have seen infest lawns like quackgrass or crabgrass does in our region. With this plant, mowing it off just encourages it to spread. Bermudagrass can't even keep it out! I don’t know what the problem with your plant is, but I would guess it has something to do with light being insufficient. It could also have something to do with the fact that it is a tropical plant growing in a house with very low humidity due to the heating system. I have never known anyone (myself included!) who has been able to keep one of these around as a houseplant for more than a few months.

Q: We bought an 18-inch dwarf Alberta spruce from the Boy Scouts. The tag said to keep inside with no fertilizer over the winter and then plant outside in the spring. Will this tree live if we plant it outside? Are there any specific care instructions? Any special planting instructions? Or should we just let it grow indoors? (Dickinson, N.D.)

A: I would be really surprised if it survived outdoors in North Dakota. The conundrum is that it probably will not survive for too long indoors either. Since Dickinson is close to being the "banana belt" of North Dakota, I would suggest planting it in a protected location outdoors this spring. Then, when autumn arrives, and before the snow flies, protect it with a burlap wrap or screen. Be sure it is planted in a modified soil that is rich with organic matter.

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: Gary Moran, (701) 231-7865, gmoran@ndsuext.nodak.edu