Water drainage for indoor potted plants?

June 23, 2009 11:46 AM

Newbie gardening question: I'm very new to gardening and have some questions about drainage. I live in an apartment, so can only grow things in containers. For plants on the balcony, I'm using terra cotta pots with a hole in the bottom and setting them on the matching saucers. But what about indoor plants? Do all pots need drainage holes?

From everything I've read, drainage seems really important for plants. But I've seen lots of pots in stores without holes. I have some nice white ones from Ikea, for example. I've also seen cool suggestions for growing plants in repurposed containers like old wooden boxes and colorful tin cans. Could you just use a layer of rocks or gravel at the bottom instead? Are some plants better suited to this than others? I'm really interested in succulents, but it looks like those need the most drainage because too much moisture is bad for them. Then again, I've seen succulents planted in open terrariums that definitely don't have drainage holes!

So, any advice on beginner container gardening? Or any book/website suggestions on really basic gardening how-tos?

posted by wsquared to Home & Garden (11 answers total)

For containers without drainage holes, you can either put about an inch of gravel/broken clay pot/glass buttons/whatever is inert and allows water to seep to the bottom then plant on top as usual. You have to watch that you don't overwater as the water will just sit at the bottom of the pot and go funky. You could add a bit of aquarium charcoal to the bottom with the gravelly stuff. Or, you could use the pots without holes as decorative containers for pots with holes.

Terrariums usually have at least an inch of gravel in the bottom, topped by something like moss which sucks up water. And, if you're using moss, to get it to suck up water, treat it like you would a dried up sponge - soak it in hot water first to rehydrate it. Otherwise, it just sits there and does nothing.

You can plant succulents indoors using mostly moss in your pots. Look for a book in the library as there are so many varieties. Some want you to withold water November through April unless their leaves shrivel, some don't want water on their roots at all but prefer you spray them instead. I just love the variety, esp fun things like string of pearls and donkey's/burro's (?) tail.

You can use old wooden boxes, although I've found those best outside as, even with a layer or two of plastic sheeting in the bottom, they tend to leak over time when the plastic starts to break down - or use a plastic container(s) inside and cover up with moss to hide them. Tin cans are OK, but they will eventually rust unless you varnish them.

If you want a fun plant, get a baby's tears. Plant it in a reg pot with a hole, then inside a pot without a hole. Fill the space between the two with water. Should be 1/2" between pots and prob a bit of gravel/stone underneath the smaller pot to bring it up to the same level. Put in indirect light as sun dries them out. They're bog plants and thrive in a wet environment.
posted by x46 at 12:00 PM on June 23, 2009 [3 favorites]

Unglazed terracotta is very porous and will wick away water with or without a drainage hole, particularly in hot breezy or sunny weather. If you are growing vegetables, it doesn't matter as much as long as you don't over water when conditions aren't right for fast evaporation. I don't know much about succulents, except that the woman I used to buy them from for the occasional housewarming gift would rave about how cacti had strong spirits.
posted by mrmojoflying at 12:11 PM on June 23, 2009 [1 favorite]

I find it's best to have drainage. If you over water, you can pour off the excess. With gravel, if you overfill it will just sit there. For those nice ceramic post, just put a plastic container with a hole, inside the ceramic pot. It's prettier than a saucer!
posted by Gor-ella at 12:19 PM on June 23, 2009

To your question, I'd say yes, all pots need drainage holes. And a quick follow-up - indoor plants need a LOT less water than outdoors. I managed to kill an "unkillable" palm by over-watering.
posted by ObscureReferenceMan at 12:22 PM on June 23, 2009 [1 favorite]

One more data point as to why it's bad if the water sits at the bottom -- some plants get diseases and fungi and generally do badly if you water them too much, and if you don't have any way for water to drain out of the soil a little, that water will just kind of pool at the bottom of the pot, and could cause these diseases/fungi/generally-doing-badly.
posted by EmpressCallipygos at 12:23 PM on June 23, 2009

Without good drainage, soil is very hospitable to fungus gnats. Annoying little buggers, even without the can-kill-your-plants aspect.
posted by Lexica at 1:12 PM on June 23, 2009

any advice on beginner container gardening?

Buy The Bountiful Container.
posted by jeb at 1:21 PM on June 23, 2009

Buy The Bountiful Container.

Seconded. Fantastic book. Oriented towards vegetable/herbs/small fruits, but generally pretty great.
posted by electroboy at 2:22 PM on June 23, 2009 [1 favorite]

Lack of drainage promotes anaerobic conditions at the bottom of the root zone, causing excess acidity and root damage. For indoor use, you can get bottom-watered pots that have a false floor between the soil and a water pool. These are not so good outdoors because they are wonderful mosquito breeding sites, but they're great indoors.
posted by flabdablet at 6:49 PM on June 23, 2009

I believe houseplants always need drainage, although I grow a few easy-to-grow plants in coffee cups. The trick with those is to let the soil dry completely between waterings. If you're not willing to do that (or the plant can't survive it) then you need drainage.

I've bought many attractive pots that have no drainage. I use them as "pot covers" - I put an inch or two of gravel or aquatic plant soil on the bottom of the drainage-free pot, then insert a slightly smaller plastic pot. It looks good, gives me minimal drainage and there's always the option of removing the inner pot if I need to get lots of water out of there.
posted by mmoncur at 9:35 PM on June 23, 2009

I've given up on regular pots and now will only use Gardener's self-watering pots. I no longer over or under water my plants, nor spill water anywhere. And they've started coming in some newer styles.
posted by evening at 4:51 AM on June 24, 2009