Perfect soil mix makes it simple to re-pot plants

Q: I have a lot of houseplants that are badly in need of transplanting. I would like to prepare a potting mix that is “lighter” than the bags of potting soil available in most stores. Do you have a recipe for such a mix? Also, any tips on getting out those plants that are stuck or root-bound in their pots without ripping half their leaves and stems off? – M.P., Dedham

A: A good potting mix for indoor plants consists of organic and inorganic materials that provide houseplants with a stable material in which their root systems can prosper and which provides adequate drainage, moisture and nutrient retention. The mix may be made with “artificial” components, ingredients that include no mineral soil, or may be a soil mix made with a base of mineral soil, specifically loam.

There are many benefits to potting houseplants in “artificial” mixes, including the fact that the components are sterilized, which minimizes plant health problems. Here is a simple recipe to follow: 10 quarts sphagnum peat moss, 10 quarts perlite or horticultural grade vermiculite and 3 tablespoons agricultural lime and 4 teaspoons superphosphate.

This formula is suitable for most houseplants. The ingredients are available at most garden supply centers and farm stores. The sphagnum peat moss provides bulk and water- and nutrient-holding capacity to the mix. The perlite and vermiculite provide air space within the root zone and aid in drainage of excessive water through the pot. Powdered agricultural lime helps increase the alkalinity of the base and reduce the acidity of the peat moss, which tends to have a natural acidity in the range of pH 4.0 to 5.0. Superphosphate adds trace elements of fertilizer to the mix and encourages root development in the newly transplanted houseplants.

As for removing stubborn plants from their root-bound pots, one simple procedure is to place one hand on the bottom of the pot and the other around the basal stems of the plant and over the top of the pot. Carefully tip the pot on its side and, while being careful to support the plant’s root ball and protect the stems and leaves from damage, gently tap the rim of the pot on the table or potting bench. This gentle tapping should release the root mass from the pot. Moistened root balls usually are easier to remove from the pot than those that are dry, particularly for plants potted in clay containers.

Q: I want to plant a raspberry patch in spring. Please recommend varieties to grow and provide guidelines for spacing so I may plan dimensions of the patch. – M.W., Troy

A: Hardy and prolific raspberries for our area include Latham, Killarney, Newburgh, Boyne Fall Red and Autumn Bliss. Your sources for raspberry plants will probably be able to provide variety-specific planting requirements, but in general raspberries should be planted three feet apart within a row and eight feet apart between rows.

Q: My gardens look wonderful June through August, but before June and after August they are really lacking. Will you please provide a list of perennials that bloom in early spring and summer and late into the fall? – R.E., Corinna

A: Certainly! Some early blooming perennials include basket-of-gold alyssum, catmint, bleeding heart, creeping phlox, primrose, cowslip, purple rockcress, cushion spurge, sweet William, pheasant-eyed pinks and violet.

Perennials that bloom in late summer and through autumn include some spectacular specimens, such as balloon flower, helenium, coneflower, alkanet, bee balm, monkshood, golden marguerite, New York and New England aster, great lobelia, cardinal flower, showy stonecrop sedum, chrysanthemum, turtlehead, mallow and some varieties of garden phlox.

Diana George Chapin is the NEWS garden columnist. Send horticulture questions to Gardening Questions, 512 North Ridge Road, Montville 04941, or e-mail them to dianagc@midcoast.com. Selected questions will be answered in future columns. Include name, address and telephone number.