Drainage hole

A drainage hole is a gap cut or molded into the base of a pot, planter or grow bag that allows water to flow out after each watering instead of pooling around the roots. Without one, water collects at the bottom of the container, pushes air out of the potting mix, and creates the soggy, low-oxygen conditions that lead to root rot, one of the most common ways balcony container plants die.

Most quality planters come with one or more drainage holes already made, often paired with a removable plug for gardeners who want to control moisture more tightly. Fabric grow bags drain through the whole surface rather than a single hole, which is one reason they rarely suffer from waterlogging. A saucer or tray underneath catches the runoff so it does not damage flooring or drip onto a neighbor's balcony below.

When shopping for containers, check the base before buying, decorative pots sold without any drainage are meant to hold a plastic nursery pot inside them, not to be planted into directly. A common mistake is drilling only one small hole in a large planter, which is not enough for heavy rain or frequent watering. Elevating a pot slightly on feet or a stand also keeps the hole from being blocked by the surface underneath.