Ask the Gardeners. Q & A

Q Would you please give a list of plants that will do well growing in water only. As I must travel a great deal, it seems that it would be the solution (no pun intended) to plant-watering problems while I'm away.

This method of growing plants is called hydroponics or hydroculture.

Many green plants (and some flowering plants) grow well in water, especially if you put a piece of wood charcoal (the size of a large bean) in the water to keep it from getting stale. You can either take cuttings from friends' plants that root easily in water, or you can buy small potted plants and wash the soil off the roots. This must be thoroughly done so no remaining soil can putrify the water.

Some good plants to try are: Chinese evergreen (Aglaonema); dieffenbachia; wandering Jew (Zebrina or Tradescantia); spider plant (Chlorophytum); arrow leaf (Syngonium); heart-leaf philodendron (Philodendron cordatum); devil's ivy (Pothos); Swedish ivy (Plectranthus); and even African violets.

Q We have an old-fashioned house with a large bathroom where I have been growing my potted geraniums, which I cut back when I brought them indoors before frost. The plants look healthy enough, but the clay pots get a green mold on the outside. Even though I wipe it off, the mold comes right back again. Will it eventually harm the plants? How can I get rid of it?

It is algae, a network of tiny plants that is encouraged to grow because of the damp atmospheric conditions in your bathroom. Some species are particularly adapted to clay pots. These have pores for the moisture to pass through so the algae can live on the food in the potting soil.

Algae will not harm the plants. If you find it unsightly, you could set the pots inside other clay ones or into ceramic containers. Some people set their pots in plant baskets. Algae do not form on plastic pots.

Q While window shopping, I noticed an attractive display of rose-hip products (teas, jellies, marmalade, and even soup) in a novelty shop. It reminded me that my mother used to make rose-hip tea and jelly. Is there a certain variety of rose that is better than others, and if so, where can I order it?

Although all seed pods of roses are edible, the ones recognized as the best source for food products are shrub roses. Hips are quite large (often crab-apple size) and are quite profuse on most varieties.

The American Rose Society has rose-hip recipes available from its office at PO Box 30000, Shreveport, La. 71130. Two sources of shrub roses are these: Roses of Yesterday and Today, 802 Brown's Valley Road, Watsonville, Calif. 95076, and Historical Roses, 1657 West Jackson Street, Painesville, Ohio 44077.

Q A neighbor has offered to give us some horseradish roots to grind up for use as a condiment. I am a bit squeamish about using the roots in the fall, as I was brought up to dig horseradish only in the spring. As the belief went at the time, the nippy vegetable wasn't fit to eat at any other time. Is this only a myth? Also, is there a nontearful method of grinding the roots?

Horseradish can be dug any time of year when the soil is not frozen. We use our food processor for grinding, adding one-half cup of white vinegar before starting. We cut the roots into chunks (about one inch). Drop the chunks into the food processor a few at a time so the blades can keep spinning as the chunks are added. Put the cover over the opening as each batch is added to keep the tears from falling in.

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