The Best Potting Soil for House Plants

With potting soils stacked in garden centers, nurseries, greenhouses, department stores and discount centers--even convenience stores and online--it's hard to know which is best for your house plants.

The best commercial potting mixes deliver water while allowing air to reach the roots; waterlogged soil kills most house plants. The best soil depends on the type and kinds of materials it contains. Buy the best you can afford for best results.

Potting mixes contain little or no soil. Garden dirt is unsuitable because it contains insects, disease and hardens when it dries in pots. House plants live in a dry environment indoors to begin with, as well as being in containers that dry out. They need a medium that provides plant support, allows air to reach the roots and can keep plants hydrated in their indoor environment without waterlogging.

The best potting mixes balance the size of the particles in a mix with the organic material, according to Dr. Claudio C. Pasian of the Ohio State University Extension. Organic bases like peat, ground bark or coir coconut wastes have sand, rocks and/or minerals added to loosen the mix and prevent compaction which kills plants. The mineral vermiculite absorbs water and releases it slowly to maintain a moist environment. The pieces also create pockets in the potting mix through which water can pass and necessary oxygen can circulate.

The best potting mix must suit your plant type. Ferns, African violets and begonias flourish in moist potting soil like a coconut or peat moss-based mix that keeps them evenly hydrated.

Bromeliads and orchids grow best in a coarse potting medium with bits of bark and twigs that keep the soil loose for air circulation and promotes drainage. Composted bark is a mix suited to these house plants.

Potting mixes with sand are best for cacti, most succulents and palms. These plants retain their own moisture in their swollen "leaves" and need soil that drains well. The best sand for potting mixes is coarse horticultural grade or well washed and free of salt and impurities.

Succulents also grow best in mixes with extra perlite, a volcanic rock with lots of holes. These store water and release it quickly, mimicking the sudden rains of a desert environment.

Making your own potting mix allows you to meet individual plant's needs. Storage requirements can be reduced with compressed coconut coir blocks that expand when they are moistened. Striking a balance between organic material such as peat moss; ground bark or coconut wastes and sand, vermiculite or perlite is not difficult and ensures the best quality materials for your house plants. Some commercial mixes contain an all-purpose fertilizer; if you make your own potting mix, add fertilizer to your custom blend in amounts suited to individual plant needs.