Q: In a recent column, you wrote about repotting houseplants, but you didn't mention orchids. Is there anything different about them when it comes to repotting? Mine have roots growing out over the sides of the pot.
A: There are some terrestrial orchids that grow in potting soil and are repotted as any houseplant. Most orchids need repotting less often than other plants. It is OK for the roots to grow out of the pot and into the air. Some orchid pots have holes in the sides to encourage the roots to grow out.
Most orchids grown as houseplants are epiphytic. They grow on other plants, such as trees in the jungle. The soil they have for their roots is just some bark and any leaves or organic debris trapped by the roots of the orchid. They need a loose and open planting media, so there is lots of air around the roots. The roots need high humidity and dampness without being swamped in water.
It is likely that your local garden center carries a bag of orchid potting soil. If you can't find a packaged mix, you can make one by mixing equal parts of bark pieces about the size of a quarter, perlite, peat moss, compost and terrarium charcoal. Some mixes use ceramic pebbles that hold moisture.
Trim off any broken or dead roots using sterile scissors. Spread the roots in the pot and pour in the potting mix around the roots. The plant should be stable in the pot without needing to be tied down. Soak the whole pot for an hour. The next watering will probably be in a week to ten days. Once you see new roots, you can resume fertilizing at one-quarter strength every other watering.
There are a couple of ways to give the orchid roots the high humidity air that they like. You can place the pot on a saucer or on some marbles or stones on the saucer and keep some water in the saucer. Since I seem to bump into the saucers on a regular basis and spill some water, I don't like this method as much.
I double pot a lot of my orchids. The inner pot has the potting media and drainage holes. The outer pot has some marbles in the bottom that are covered with water. The inner pot sits on the marbles and as the water evaporates, the orchid roots are surrounded by humid air.
Jeff Rugg's weekly column, "A Greener View," can be found at creators.com.