In New Mexico, I'm experimenting with indoor gardening. Not houseplants, but rather lettuce and anything else I can get to grow for our culinary delight. Built into the solar hallway floor are two planting boxes, each about 2' wide, 8'long, and 30" deep.
I'm getting them ready for duty. At right is how they looked just after The Plumber installed the drain standpipe in each planter.
From our stony back yard, I harvested 3-6" chunks of volcano rubble (our geology is ancient and formerly molten) and layered them 8" deep in the bottom of the planter to facilitate drainage and to take up space. I dropped the stones in one at a time so I didn't break a window.
I could have filled the entire 30" with soil, but garden vegetables can't take advantage of soil that deep. Also, we have lots of stones and I want to get them out of the way.
Then I covered the stones with landscape cloth ($6 for a 50' roll at Ace Hardware).
The cloth will keep the next layer (gravel) from settling into the stones. The gravel is going to have to wait a while until we figure out how to pay for it.
It's not that the planters will use very much gravel--only 4-6" each. It's that the driveway will use considerably more; the planters will get the leftovers.
12/10/09 - The planters won't get leftover gravel from the driveway after all. The driveway gravel is something called base course, which isn't suitable for use in an indoor garden. There's other gravel in the works.
I've been thinking for several weeks how to achieve a way around the tendency of plants to lean toward the light. If a light-loving plant is surrounded by sunlight, the way they are in an outdoor garden bed, they stand up more or less straight. If a plant lives in a shady place, it can develop a decided lean as it reaches for light. A houseplant has to be rotated periodically to keep it from leaning, or from developing all its growth on only one side.