Quality is important in everything we purchase, especially if we want the product to last. Containers for plants are no different. Clay pots can be easily cracked and broken so it's important to select a sound pot instead of one with an invisible flaw that may crack easier. To check for soundness, hook a finger through the drain hole and tap the pot on its shoulder (the expanded rim of the pot). A good pot will ring like a bell (flawed pots will produce a flat or dull sound). Clay pots are baked in kilns and get their strength from the duration and temperature at which they were fired. The longer and hotter they are fired, the better the minerals within the clay will harden or vitrify. When selecting pots, you can easily detect low quality pots by running your fingernail across the pot. Low quality pots scratch easily. Walls of inferior pots begin to flake, pit and crumble as mineral salts leach through. Durability is affected by the purity of clay used. All clay contains lime impurities. In quality pot construction, the lime is filtered out of the clay before manufacturing. Inferior pot manufacturers usually don't bother with this process and allow lime deposits to remain. Lime particles absorb more moisture than clay particles which causes blistering and flaking of the pot surface. If the pot you are selecting has white, gritty spots on the surface, pass it by, it's an inferior pot. Clay that contains sand is made into quality pots as long as the firing process is done correctly. Pots properly handled will be dense and ceramic-like. Improperly handled pots will have a sandy texture and are likely to crumble away with time.
The quality of plastic pots can be determined by checking the thickness and flexibility of the pot walls. Pot walls should be thick enough to support the weight of the wet soil they will hold. The larger the pot, the thicker the walls should be. Flexibility can be checked by squeezing the pot. Plastic pots should be flexible enough to withstand being bumped or dropped without breaking. Generally speaking, the durability and thickness of the pot increases with increasing cost. If planning to use a particular plastic pot outdoors, check the label for an indication that it has been protected with ultraviolet light inhibitors. These inhibitors will help protect pots from fading and becoming brittle. The label may not say specifically that it was treated; however, if labels recommend using the pot outdoors, it probably has this protective treatment.
Price is not always a reliable indication of quality. Some inferior products are high priced as well. With the help of this article, I hope you'll be able to select high quality containers for your plants.
This article originally appeared in the March 16, 1994 issue, p. 23.