Drainage is crucial for potted plants. In order to grow properly, their roots cannot sit in water at the bottom of their pot. Some types of plants require drainage materials be mixed in with their potting soil to keep even a small amount of excess water from remaining in the potting soil after watering.
Primarily used in the bottom of the pot, a layer of gravel will collect excess water and keep the soil from being saturated. Use 1 inch of gravel in smaller pots and up to 3 inches in pots over 8 inches in diameter.
A piece of broken terra cotta, referred to as a “pot shard,” is used to cover the single large drainage hole in terra cotta pots. It allows excess water to drain out but keeps the soil from washing out the hole as well.
Used in place of a layer of gravel, non-biodegradable foam packing peanuts perform the same drainage function. A single layer works for pots up to 6 inches in diameter. For pots larger than 6 inches, use a 2- to 3-inch-deep layer for pots larger than 6 inches.
Mixed into the potting soil, coarse sand creates air spaces around its irregularly shaped particles, allowing water to drain more freely from potting soil. Primarily used in potting mixes for cacti, succulents and orchids, coarse sand lightens the soil mix and keeps it from retaining excess moisture, which these plants prefer.
Shredded Bark and Coir
Shredded pine or cedar bark and shredded coconut hulls, called “coir,” are other materials added to potting soil to facilitate drainage. These shredded materials are added to the potting soil or used in place of potting soil to grow orchids and other epiphytes that require a loose growing medium that drains readily but allows the roots to take up moisture. Shredded bark and coir hold enough moisture for the plants to use and their rough, irregular size particles allow water to drain out of the pot quickly so the roots do not sit in water.