The importance of adding drainage materials to the bottom of houseplant pots is a long-held gardening myth. Photo: Kallihora, depositphotos
By Larry Hodgson
Question: Why don’t nurseries put gravel in the bottom of their houseplant pots anymore? Every time I buy a houseplant, I have to repot it to add a drainage layer at the bottom. You’d think nurseries would do this so the plants can grow well.
Answer: If nurseries don’t put a drainage layer of gravel, pot shards or clay pebbles in the bottom of the pots of the houseplants they sell, it’s not out of laziness or lack of concern about their client’s success with the plant. They don’t do it because it’s considered poor horticulture!
The idea that a drainage layer at the bottom of a pot with drainage holes was of any use to the plant was debunked years ago. Already by the 1950s, many tropical plant producers had stopped putting a drainage layer in the bottom of the pot, claiming it left the plants subject to rot. Then studies by the late Bonnie L. Appleton of the Polytechnic Institute and State University’s College of Agriculture and Life Sciences back in the 1980s, notably, showed plants grew better in pots that were filled with potting soil right to the base … and that such pots actually drained more efficiently than pots with a drainage layer. A drainage layer pushes the “perched water table”—a zone that tends to remain overly moist—up, reducing the space for roots to grow and function properly, cramping the plant and possibly causing its slow demise.
And even in terrariums and pots with no drainage holes, water tends to accumulate in the so-called “drainage layer”, then migrate up into the root zone due to capillary action where its continued presence leads to rot.
The next time you buy a houseplant, you may need to repot it for various reasons (maybe it’s overgrown, the pot is too tight, the plant needs a change of soil, etc.), but certainly not in order to put a drainage layer in the bottom.
When it comes to drainage layers, just bury that idea!