When it comes to choosing between plastic or clay pots, each has advantages and disadvantages. Plastic pots are economical, lightweight, easily cleaned. They come in various attractive colors or clear, and quantities can be stored in a small space. They do not absorb moisture from the soil, as clay pots do, so you do not need to water plants nearly so often.
Clay pots come in one color, brick red. They are heavier than plastic, difficult to keep clean since contact with moist soil encourages algae to form and salts to collect, and they take up a lot of room, but clay does let roots "breathe" through the porous walls. I use both kinds of pots with equal success, but I incline toward clay, especially for large plants, because clay pots provide a more substantial base. If, on a hasty occasion, you water too heavily, clay pots compensate for your error more readily than plastic will, they are far more forgiving to excess water.
Peat pots, round or square, come in 1 1/2- to 4-inch diameters. Lightweight, easy to handle, they are ideal for use when transplanting seedlings from flats. With peat pots, a second transplanting is unnecessary, for roots grow right through bottom and walls, and some peat pots even contain fertilizer. Since peat pots need not be removed from plants when it is time to transfer to larger quarters or to the garden, growth is not checked as in usual transplanting, and plants receive no setback.
To keep pots of every kind and size handy, store them under benches. If you have a piece of corrugated asbestos cement-board left from your benches, use it below for storage. Nest the pots and lay them in the gulleys of the corrugations where they will stay uniformly in place.