Has anyone tried using burlap sacks, such as the kind used for coffee beans, as planters? I was eyeing Smart Pots but I already have several of these burlap sacks around the house, and they'll be the perfect size for indeterminate tomatoes or squash if I fill them halfway up with dirt.

I think they would have all the upsides (air pruning) and potential downsides (drying out too fast) of Smart Pots. They might rot out in the bottom after a season, but I'm okay with that, and they're free. They'd be placed on mulch in my backyard.

For soil I want more water retention, so I'm thinking 50% compost (Bumper Crop) and 50% potting soil or 5-1-1 mix.

Any thoughts? Dire warnings? Praise for my ingenuity? ;)

(I'm in zone 10a, Oakland, CA. We don't get summer rain, so I'll be hand watering.)