What Mix to Use for Starter Plants

Vermiculite

• Vermiculite is one component of artificial potting mixtures for starting plants. It's a natural silica product mined from the earth and heated to 1,100 degrees Fahrenheit to "pop" the layers apart. The resulting product is light and fluffy, able to hold water within the crevices but also the air necessary for healthy root growth. Vermiculite should be at least half of your mixture, although some gardeners use vermiculite alone for rooting cuttings such as geraniums or rosemary.

Humus

• Humus is the decomposed organic material within soil. You can usually purchase bags of humus from garden supply stores. Humus retains moisture and supplies nutrients to the soil, ready for uptake by the young plants. Plan on incorporating about five percent humus to keep your mixture well aerated.

Perlite

• Perlite is another mined substance that you often see in potting mixtures. The pieces look like small, white softballs. Perlite is a natural glass but when it's heated to 1,600 degrees Fahrenheit, the fragments pop like popcorn into much larger pieces -- 13 times larger than the original. Perlite acts like vermiculite in keeping water and air close to the plant roots. Since perlite acts similarly to vermiculite, use either one as half of your mixture, or a 50-50 combination.

Peat Moss

• Peat moss is an organic growing medium amendment -- the partially decomposed part of peat bogs. Since it's sterile, peat moss is often used as a large part of soilless potting mixtures, good for starting plants. Peat moss is sold in bags as a finely shredded product. This material works well to increase soil aeration and moisture while keeping the weight down. Make sure to wet it thoroughly before trying to add it to potting mixtures. Fifty percent of your starting mixture can be peat moss.