Houseplant Myths: A "drainage layer" can take the place of drainage holes

Let's bust some houseplant care myths!

The Myth:

A “drainage layer” of gravel or pebbles or potting shards at the bottom of a pot can take the place of a drainage hole in a pot without one.

The Truth:

A drainage layer does not improve drainage, and they can actually make it worse. Studies have shown that water does not move easily from a finer to a more course material, so it’s difficult for the water to move from potting mix (a finer material) to the drainage layer (a courser material). That means using a drainage layer will actually keep your potting mix more waterlogged, not less.

In a pot with a drainage hole, a drainage layer is actually keeping your potting mix from draining well so that it can release the excess water out of the hole. In a pot without a drainage hole, not only does the water in the potting mix not drain well into that drainage layer, but the initial water that actually makes it down there has nowhere to go, especially in pots made from non-porous materials. This means there’s a little pool of water at bottom of the pot that is waiting for your plant’s roots to grow down into it and if they can’t drink it up fast enough, they’re going to suffocate and get root rot.

The bottom line is that even though this has been something recommended in many books, by many companies, and many people, drainage layers just aren’t doing any good and actually can do harm. And if you still have doubts, remember: no grower ever grows a plant in a pot with a drainage layer or in a pot without many drainage holes! If this was a good system, the people who make their money off of growing healthy plants really quickly, efficiently, and well would be doing it.

Solutions

- Use pots without holes as cache pots, keeping your plant in a plastic grow pot with plenty of great drainage holes.

- Drill at least one, preferably several, holes in the bottom of the pot (you can check out a reel on our Instagram account showing how to drill holes here.)

- If the pot is clear glass and you don’t feel comfortable drilling it, use a clear, plastic liner with holes as the “grow” pot so you can still see straight thru to the potting mix (orchids are often sold like this). 

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