UPDATES, some of which prove those who post comments are pretty darn smart:
I saw 25' of weed barrier for $7 at our local OSH; if you spread this over 7 bins (a good estimate), it's $1/bin, bringing the total to under $15, including the tomato plants.
The clear bins DO promote some algae. The real one I have (green exterior) just got dumped out, checked and cleaned and has no algae in it. My recommendation - go with something other than clear if you can find plastic you trust.
If you drill or cut holes for the top, make them bigger than you think they should be. I had plants rub against the cuts, and, well: cut plants. So, I have put some paper around the surviving plants (the plants are too big to take out to re-cut the lid). I'm trying to reseed in some of the holes, which should be interesting.
Step 1: Box and Water Layer
Step 2: Dirt Holding Layer
Step 3: Keep Soil and Water Separate
Step 4: Water Supply
This is a half litre bottle from Costco someone tossed at work. I have also used the skinny ones, but I had to get 2 pushed together. To do that, I cut about a half an inch off the bottom of one, then carefully pushed the neck of the second one into the bottom of the first. The ridges mated and I had a longer water spout. I wanted to use one from TJ's organic ketchup, but I couldn't get the label off for love or money (soaked in water for 3 days). Some helpful souls have given suggestions (see the comments), but I'm still striking out--I have a 2 year old ketchup bottle in the garage right now. That failure still annoys me, as the bottle is a good length and otherwise demands little real estate.
Step 5: Fill With Dirt
Add dirt, pat down, add some water to help compact, repeat until you have the dirt level where you want it. I used store-bought dirt, some "castings" from my worm bin, a touch of compost, and some lousy dirt from the lousy soil here.
I added fertilizer right after this photo. It seems to me the two big secrets of these bins are water control -- lots of water without root rot -- and lots of fertilizer, which gives the organic part of me the creeps, so I use less. The small secret appears to be the lid to keep evaporation, weeds & intrusions down.
I do not have a great idea for the top -- I was thinking of cutting a few large holes in the lid, and putting a garbage bag across the bin, snapping the lid on, and putting the plants in place through cut Xs in the plastic bag. Just using the lid might work (but creates a permanent pattern). Or, I may leave it open and deal with the evaporation--see my comments on the wine barrel on the next page.
Tomatoes, pole beans and peppers are on the agenda.
Step 6: Wait for Growth
Also, I did this with a wine barrel (you might see it in the background of the rock shot) last year. I didn't do anything about a "top," as it was decorative and looked great with flowers, chive, one garlic clove and beans. Over the winter (Northern CA), we had marigolds from seed November - March (still there, for about 18 months until the lawn mowing guy tore them out).
Next up, I need a trellis for the beans. This may be a couple of 2x3s and some of the wire "fabric" they use to reinforce concrete. I hear they do great holding up tomatoes, too. Or it could be string, like last year.
Some Updates: Mixed results on tomatoes, but I liked it. Beans didn't do as well -- maybe they had too much need for water.