January 16, 2003

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: Can you tell me how to get rid of mold in the soil of a houseplant? (E-mail reference)

A: Either repot with fresh, pasteurized potting soil in a sterile pot, or simply scrape the mold off and work up the surface to encourage drying. Reduce watering frequency.

Q: I received a blooming shamrock as a gift. I have followed the directions exactly, which specify to water from the bottom up, put a plastic bag over the top and put under light in a warm place. Now I have mold growing on top of the pot. Can it survive? Should I throw out the growing medium and start from scratch? Can I take the bag off so the plant can dry out? Can mold spores get into the terra cotta pores? Should I get rid of that too? (E-mail reference)

A: If the mold is not on the plant, you have nothing to worry about - yet. Take the bag off and allow it to dry and it should be ok. Next time don't make the bag covering the pot so tight. The plant needs some ventilation to keep it from molding. You can scrape off what is growing there now, once it dries up somewhat.

Q: I have a tree hibiscus inside for the winter and a few weeks ago I noticed that some of the leaves were turning yellow. I just plucked them off and thought nothing of it. As time went on I noticed no improvement no matter what I did. It had spider mites but I treated it with Shultz insecticidal soap. That took care of the mites but the leaves keep falling. Upon close inspection I see that the leaves are splotching from between the veins and epidermis and spreading in every direction. On the underside of the leave there are tiny brown specs but I don't know if that is caused by spider mites or not. This is happening to all of the leaves and I don't want to treat it until I know what it is. (E-mail reference)

A: Allow the plant to die down by reducing the watering. Keep just enough water in the soil to keep it from drying completely. Keep the plant in a cool location, then in about 6-8 weeks, cut it back, place it in a sunny window, and begin watering normally again. It should start putting out some new growth. When active growth is evident, fertilize about once a month with a houseplant fertilizer such as Schultz's or another product.

Q: We recently purchased a home just north of Jamestown on the west side of the reservoir although we are not directly on the water. We are in the process of purchasing two lots adjacent to our property. The lots currently are in grass with windrows on either side on the one parcel, and a grove of trees on one side of the other parcel. My thought is to turn much of the grass area into prairie. I am looking for information on the types of grasses and forages to plant for this area and resources for the seed. Jamestown is apparently the transition area between the tall grass and short grass prairie. At our prior home in Rochester, Minn., we put our side yard into tall grass prairie. While developing our prairie in Rochester, I worked with a man who took care of killing the existing turf grass (using Roundup and a broad leaf herbicide) in the area I had marked off for the prairie. He later burned the grass and disked the ground. We hand broadcast the grass and forage seeds. What method would you recommend to develop the prairie here? Do you know someone in the area you could refer us to as a ground preparation person? (Jamestown, N.D.)

A: The procedure you followed in Rochester should work fine where you are now located. I would suggest going back to the nursery you used in Rochester for advice as to what and how much to plant, since they are the experts. I don't know of anyone who would specialize in developing the site for you, but perhaps the nursery folks would know of someone. Maybe someone who reads this will know. If the latter turns out to be the case, I will have them contact you.

Q: I have a spider plant at my office that is sitting under a flourescent light and is doing beautifully. A few questions about it though. I occasionally get brown spots on the ends of the leaves. When I do, I cut back watering but now I'm noticing rust colored markings running lengthwise down the sides of the leaves. Is it due to improper watering? How do I know when to transplant the spider? It's in about the biggest pot I'd want at my desk at work but I've found roots starting to poke up through the soil. At first it was mainly the feathery small roots but today I found a thick one coming up. The plant also keeps dividing in the pot and coming up as two plants. I've split it twice, giving a full sized plant to two friends. Why does it keeps splitting? (E-mail reference)

A: You simply have a vigorous spider plant! Be happy - and keep dividing it and giving one away to friends. Your cutting back on the watering is simply concentrating the salts that exist in your soil and/or water. Maintain a normal watering schedule like you obviously have, and the plant should be alright. The brown tips on the leaves are due to the chlorine/fluoride salts in the water or soil. This plant is sensitive to them but should not keep the plant from being productive. You can alternate watering with distilled water to reduce the tip browning.

Q: Is it true that human hair can stop deer from feeding on my plants? If so, how much? (E-mail reference)

A: Human hair is just one of the methods used to discourage deer feeding. Hot pepper spray, Irish Spring soap, predator urine, etc., are also used. They should be cycled when the deer have become indifferent to the one in current use. There is no data that I know of that prescribes the intensity of distribution. Just make it more than you think necessary and it may work.

Q: I have a jade plant with leaves that are shriveled and dropping off. I know that I haven't watered it too much. I have noticed a sparkly coating on the leaves. The leaves that fall off have a crystal-like sparkly substance that comes off on my hand. It was only on one plant, but now it seems to be on my variegated one as well. I sprayed it with pyrethrins but then read that you shouldn't use it on jades. What will it do to my plants? (E-mail reference)

A: I would suggest starting over again with new plant material, as your description isn't too encouraging. I can only guess that the substance that you describe as coming off on your hand is a mold of some kind.

Q: I have a ficus that is 19 years old. It has been through a lot and now it has, on the back of most leaves, a small white spot where the leaf and stem start. When I scrape it off, it is black underneath. The white spot looks a little like a spider web. What can I spray it with? (E-mail reference)

A: It is likely scale which is getting started on your plant. I would suggest getting some rubbing alcohol and q-tips. Dip the end in the alcohol and rub the scale off completely. This is the most effective way of controlling this pest. Sprays are not effective as the pest’s covering can keep the insecticide from reaching the insect. Be thorough as one scale can easily multiply into hundreds in a very short time!

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.

###

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