By Michele Wach
Special to the Denver Rocky Mountain News

Question: Our family would like to try indoor composting using worms. How do we begin?

Answer: Composting using worms is called vermicomposting. It's a fun composting practice for the whole family, especially if you have limited space.

To construct a worm bin, use a plastic container with a lid. You will need a 1-foot-by-2-foot-by-3-foot worm box to compost scraps from a family of four to six people. Fill the box with bedding material, using between nine and 14 pounds. Bedding material can include slightly chopped leaves mixed with compost and straw or shredded newspaper. Don't use leaves by themselves, as they might mat down, reduce air circulation and cause odor problems. You also can use shredded newspaper mixed with peat moss or garden soil. After filling the box with bedding, moisten it with water until damp but not wet.

Now you are ready to add the worms. The usual nightcrawlers found outdoors are not suitable for vermicomposting because they prefer to dig deep burrows in large amounts of soil and require soil temperatures of around 50 degrees. Redworms are preferred for indoor composting. In the Denver area, you might ask about buying them at garden centers and nurseries. Some bait shops also carry them. You might be able to order them, but they can be sensitive to cold, so be certain they will arrive well-insulated — and alive.

Redworms come to the surface to feed and then drag the food down into their bedding. Worms can eat their weight in organic matter each day. A pound of redworms will process a pound of organic material daily. The worms, however, also will eat their bedding, so expect a pound of worms to eat about one-fourth to one-half of their food scraps each day. The box will yield some moisture so periodically drain the box to keep the worms from drowning.

You can feed the worms kitchen scraps, such as apple peels and lettuce. Do not, however, feed them dairy or meat products because these foods attract flies and cause unwanted odors.

Worm castings should be removed once a month. Do this by adding the scraps to only one side of the worm box. The worms will move where the scraps are. Feed them on the one side for several weeks allowing the other side of the box to be clear for casting removal.

The worm castings make a wonderful soil amendment for the garden!

Question: Some of my houseplants have a white crust on the soil surface. Will this hurt my plants?

The white crust on the surface of the potting mix is a build-up of soluble salts. These salts come from the potting mixes themselves, from fertilizers and even from the water used to irrigate the plants. Excess salts never drain away completely because water is caught in saucers below the plants and it then is re-absorbed. Try placing gravel under the pot, in the saucer to allow water to drain out without being re-absorbed.

Excess soluble salts can be harmful to plants. These salts can cause root damage, which then leads to problems with water uptake. Soluble salts also can cause damage to foliage. Wilting, yellowing and scorching are associated with salt problems.

A soluble salt problem can be improved by leaching the salts from the soil. Start by removing the white crust from the top of the potting mix. Also, scrape excess salt from the outside of the pot, around the drainage holes and in the saucer. Then remove about one-half inch to two inches of the potting mix. Do this carefully so roots are not damaged. Next, remove the saucer from the bottom of the pot and place the whole plant in a sink or bathtub where water can drain freely. Using tepid tap water, fill the pot to the top several times allowing the water to drain out completely. In severe cases, the pot should be filled and drained six to eight times. Place the saucer back under the plant, add new potting soil to fill and water lightly.

Michelle Wach is a Colorado State University Cooperative Extension horticulturist in Douglas County.