re-potting indoor plants
I have several different kinds of indoor plants, and while know that most re-potting should be done in the spring, I don't know what diameter pots to use. Is there a guide for this? Plant height to pot diameter? Thanks. Marie McWilliams
Baltimore County Maryland
Pot size needed will partly depend on the plant in question - some like to be "pot-bound" and snug in their pots while others want more room. For those needing a step up, usually increasing the pot size (diameter) by one increment at each repotting is recommended. Increment amount varies with pot size - for smaller pots increments are in the one-half to one-inch range, and for larger pots (perhaps over 6" diameter or so) they increase by one- or two-inch increments. For example, you can take a 3" potted plant to a 3.5" or maybe a 4" pot, and a plant currently in an 8" pot to a 10" pot as the next size up. Increasing size too drastically increases the risk that roots can stay too wet between waterings or that the soil will "age" too much before the plant runs out of room and needs repotting again. (Age here refers to natural compression over time as some of the ingredients break down, which retains more water, plus the accumulation of "salts" from fertilizer minerals that do not leach out of the soil sufficiently during waterings. You can of course repot before this happens and just re-use the same pot with fresh soil; it's just that this merely adds to the plant's maintenance.)
If you have orchids, they need to be repotted with more regularity than other potted plants as their mix should not be allowed to degrade. This means that an orchid may not necessarily have outgrown its pot by the time the media has degraded to the point that it contains too much mineral buildup and retains too much water, as orchid roots are quite sensitive to these conditions. Here too this depends on the orchid type and the kind of media it's potted in, but in general, repotting them once a year is a good idea.