Water can "perch" above perlite if the soil you're using supports perched water, and that can be a problem. Ballast is the way to go. Use old soda bottles, milk jugs, bricks. I don't have access to my photo cache from this puter, but I'll try to post a picture to illustrate why using objects for ballast that allow the soil to have one or more continuous soil columns that run uninterrupted from the top of the soil line to the bottom of the pot are preferable to "a drainage layer"

Al

Thanks Al, I will make sure to use something that allows some top to bottom contact between the ground and the soil layer. After reading your posts in container gardening I have learned to NOT use a layer of rocks in my pots and I should have realized that perlite would do the same thing...move the water table up. I have access to free large styrofoam heavy duty coolers. I wonder if they would degrade over time? I will see if I can get someone with a big family to save milk jugs for me :) Julie

The coolers would probably work, but the last thing you want are peanuts. Between the roots, soil, irrigation and peanuts, it becomes an awful tangled mess.

Once, long ago... before I knew Al or had read his extremely helpful information... I made the mistake of filling the bottom half of some very large pots with styrofoam peanuts.

What a messy mistake that was!

Luckily, I only grew annuals in them. I only wanted the pots to be lighter so I could move them around easier by myself.

Lesson learned, though! That top half, which was very poor bagged potting soil, became hydrophobic and floated on a bed of peanuts! And removing the roots and separating out the styrofoam to dispose of was a job!

I would definitely go with something like milk or water jugs, or large soda bottles... something like that. If a few people save them for you, it shouldn't take long to accumulate the amount you might need.

I use large chunks of styrofoam all the time. I save all the packing material in boxes, use old coolers, anything that has large pieces.

Keeps the pots light and allows me to plant shallow in big pots. Easier to take the plants out without peanuts flying all over. I do use peanuts on my orchids and they work well in small pots.

Jane