Pot Materials: Which Ones Breathe and Which Ones Only Look Good

Every pot does two jobs. It holds the plant and it manages water, and the materials sold for the purpose do the second job with wildly different levels of competence. Weight, appearance and cost come after that, and it is worth deciding which of the two jobs a container is actually being asked to do before buying it.

The ones you can grow in

Unglazed clay is the working pot. Fired from ordinary clay, cheap, rough-looking, and the best of the common materials at letting air and water move through the wall, which is why nursery and transplant work is done in it and why it so often goes inside a better-looking container. The trade is that a clay pot dries out faster than the plant inside it always likes, so in a heated room it means more frequent watering rather than less.

Plastic is the other end of the argument: light, inexpensive, available in any colour, and almost completely closed. Nothing breathes through the wall and no water escapes except out of the drainage hole, which cuts the watering chores and also hides a wet root zone from you. It is the standard container for soilless culture and for the indoor foliage plants it is chosen for, and it is the pot in which overwatering does the most damage.

The decorative ones

Glazed porcelain and the fine purple clays are made to be looked at. Their surfaces are sealed, so they behave like plastic with a better finish, and they are best used as cover pots with the plant left in its clay or plastic liner. Marble and sandstone are the same argument with more weight, and natural stone is heavy enough that it belongs on a floor rather than on a table. Cement is sturdy, lasts outdoors for years and can be finished in almost any colour, but it is bulky and closed, so it suits small trees and bonsai-style plants that will not be moved, with a layer of moss over the soil to make the whole thing look deliberate.

Three that need modifying before use

Metal has no permeability at all and rusts from the inside out. Drill a drainage hole in the base, line the interior so water stops standing against the wall, and treat it as an outer pot for anything that dislikes wet feet.

Wood breathes and rots at the same rate. It needs preservative treatment, which makes it a poor container for anything you intend to eat, and even treated it is a two or three year pot.

Water basins, the wide shallow kind with no hole whatsoever, are exactly what they sound like: for plants that live with their roots under water, and for nothing else.

Whatever the material, the drainage hole is the detail that decides whether the plant lives. The size question and the mix that goes inside are worked through at pot choice for daphne, and the case for deliberately under-potting a plant that rots easily is argued at money tree care. What the pot is filled with matters as much as what it is made of, and the granular mixes are covered at granular potting media.