Outdoor planters, what to use for drainage.

Outdoor planters, what to use for drainage. (post #16726)

kathryng on Mon, 04/12/2010 - 07:27

General Gardening

I need some advice on what is the best thing to use in the bottom of my large and small outdoor pots, that would help with the drainage. I have always used small rocks/stones, and I've been recently reading that this may not be the best thing to use. I tried using newspaper once and this didn't work for me. Any input would be greatly appreciated, thank you.

Bathtub effect (post #16726, reply #1 of 5)

by kmrsy in reply to kathryng [original] on Mon, 04/12/2010 - 18:50

Using rocks to enhance drainage is a myth and actually can create the opposite effect. Experiments show that moisture will not move from one type of medium to the one below it until it reaches the saturation level. This keeps too much moisture in the uppper growing medium leading to root rot. It's called the bathtub effect. Instead you should use a uniform, well-draining soil mix throughout the container.

_^..^_ Kitty, neIN, Z5

pot drainage (post #16726, reply #2 of 5)

by annette39 in reply to kmrsy [original] on Mon, 04/12/2010 - 23:23

Ihad also read that one should use only a good soil mix. But it makes large pots really heavy. I often used crushed aluminum soda cans. Stopped using "packaging peanuts" quite a while ago. Really a mess when you empty the pot at summer's end.

You're gonna carry that weight / Carry that weight a long time (post #16726, reply #4 of 5)

by kmrsy in reply to annette39 [original] on Tue, 04/13/2010 - 15:13

Uniform, well-draining soil or soil-less mix doesn't have to be terribly heavy. Be sure to include a fair amount of perlite. This reduces weight, promotes drainage and air circulation. A good compost or sphagnum peat is lighter in weight than topsoil. Vermiculite is light weight and, being a clay, provides good cation exchange. And, if you know when you'll be moving the container, you might try letting it dry out a bit just prior so the weight of the water doesn't add to the heaviness.

_^..^_ Kitty, neIN, Z5

Drainage in planters (post #16726, reply #3 of 5)

by KimmI in reply to kathryng [original] on Tue, 04/13/2010 - 04:08

Just using a good quality potting soil (a soilless mix) or my compost has provided good drainage in the outdoor planters I have. I've never had to put stone, gravel, pot shards, or anything else in the bottom of these pots. I have just put in something, newspaper, coffee filters, fiberglass screen, to keep the potting soil from flowing out of the drain holes, but nothing else.

Just be sure the container itself has provision for drainage, and that those drain holes are not blocked in any way.

The sign of a good gardener is brown knees, not a green thumb.

I use a coffee filter or two (post #16726, reply #5 of 5)

by flee in reply to kathryng [original] on Wed, 04/14/2010 - 08:04

I use a coffee filter or two to prevent the soil from spilling out the holes.

Flee~~Zone 5 Mid-Michigan

Outdoor planters, what to use for drainage.