We've all been there. In Target, looking at a cute cheap planter from their newest home collection. Or spotting some gorgeous glazed pottery that would be just perfect for re-potting the white bird of paradise in your bedroom. The colors are perfect, the price is right. There's just one problem: There's no drainage hole. So you ask yourself: Is it really that bad to keep plants in pots with no drainage hole?
The short answer is yes, but there's also a workaround. Here's the deal:
Why Drainage Holes are Important
There are three main reasons that drainage holes are important: 1) they allow water to drain from the soil and through that, they enable 2) good airflow and 3) the flushing of salts from the soil.
Even plants that enjoy a good soaking and perpetually damp soil don't like to have their "feet wet." When roots sit in water for too long, and when air isn't allowed to flow freely (as in the case of saturated soil), the plant can develop root rot, which is almost always an irreversible condition for the plant. In other words, plants soaking in water is one way to ensure their early demise.
In fact, root rot caused by overly damp, poorly-draining soil can be a problem especially for plants that enjoy moisture. You want to give them a good amount of water, but with no place for the water to go, you may be slowly rotting its roots as mentioned above.
But there's another, less straightforward possibility as well: Knowing that you don't want your plant sitting in water and knowing that there's no outlet for drainage, you may be overly cautious and not give the plant as much water as it wants.
For plants that prefer more dry soil, under-watering on purpose doesn't seem to be much of an issue. But then we're back to the wet feet issue again. Plants that don't like a lot of moisture will need a drainage hole for moisture to escape and for airflow to circulate through the pot.
Another important function of drainage holes is to allow water to flush the soil of excess salts from fertilizers. As SF Gate puts it, "If you water with a fertilizer solution, the salts also build up in the soil and, without drainage holes, you cannot run pure water through to rinse out the salts."
How to Use Pots with No Drainage Holes
Some experts suggest using a layer of pebbles as a sort of drainage layer in those pots without drainage holes. This technique allows excess water to flow into the space with the pebbles, away from the the soil and therefore the roots of your plant. Others caution against this method, going so far as to call it a "myth," saying that water has trouble flowing between the two different mediums and will therefore stay within the soil—even if pebbles are beneath it.
But there's still a way to use those pretty pots that don't have drainage holes! Plant your plant in a porous pot with a good drainage hole, like the classic terracotta pot, and then place that pot within the larger decorative, no-drainage-hole pot.
When it comes time to water, if the plant is small enough, you can take it out of its decorative pot and take advantage of the drainage hole. Alternately, you may place gravel or pebbles in the bottom of the decorative pot and place the functional pot with drainage on top of it. In this scenario, gravel can function to keep the plant's roots away from sitting water. Furthermore, this setup allows for ambient humidity, which is a boon to many plants.
Note: Pots without drainage holes should never be used outdoors where your plant will get rained on because you have no way of regulating the amount of water your plant receives.
So go ahead and use and enjoy those beautiful pots without drainage holes—but do it wisely and never at the expense of your precious plants.