Question
Why are plastic pots used for orchids?

Answer
Mary Ellen, thanks for  your question. Plastic pots have a number of features not possessed by clay pots. The main features are light weight and protection of the potting mix from rapid drying.  Plastic is impermeable to moisture. On the other hand, clay pots are heavier and the walls of clay pots contain many air pockets that allow moisture to pass through from the inside to the outside of the pot and, hence, more rapid drying of the potting mix. Plastic pots are ideal for phalaenopsis that usually are not top heavy and the plastic pot is stable. If you pot in plastic and the flower spike, flowers, etc tend to make the plant top heavy, the plastic pot can be placed inside of a heavier clay pot for stability. Another feature of plastic pots is that some come in a clear plastic which allows light to penetrate to the roots.  Orchid roots possess chlorophyll and hence are photosynthetic.  Clear plastic pots also permit the monitoring of root health in the pot.  I prefer clay pots for heavier plants such as cattleyas.