Most of the vegetables we're using in this project are from farmer's markets or local farms. So far we've hit Drumlin farm, Land's Sake farm, the Kendall square farmer's market, Pound Ridge NY (lame!) and last year we also did some of Central and Harvard Squares and BUSA farm.
But the most local produce is from plants you grow yourselves. I've mentioned the herb plants we have on our porch (basil, chives, oregano, parsley, sage, rosemary, and thyme) and we also have alpine strawberries, 4 tomato plants, and a sweet red pepper. I put in fresh soil this year (the previous was 3 years old) and the results are pretty good- no tomatoes or peppers yet, but the grape tomatoes are starting to ripen.
What if you don't have a sunny porch, roof deck, or yard in the city? We also have a plot in a community garden that we got several years ago. It's an 8x12 piece of dirt with a water source, and we pay $5/year for common expenses. Cambridge has many of these (14 according to this) but it's not always clear how to get one. You need to contact the Cambridge Conservation Commission and they'll put you in touch with the coordinator for the garden you're interested in. When we got an apartment in mid Cambridge, we signed up for several and ended up with a plot pretty quickly, and then back about others over the subsequent years, so it seems like the waiting time can be anywhere from one to several years.
Other cities also have similar programs. Boston has several with available plots, including one near the Publick Theater in Allston and an enormous one in the Fens. Somerville also has 8 small ones.
So what can you fit in an 8x12 plot? More than you might think. Here's a view of the whole thing with different crops labeled.
The key in a small space is to grow vertically. Cucumbers, pole beans, peas, and tomatoes can all be trained up a stake or cage.
Here are some of the tomatoes we're growing, which includes some standard (super 100 cherry) and some heirloom (Brandywine pink, Mr. Stripey red & yellow striped) and one I forgot to label- it will be a surprise!
They seem to be doing better than ever this year. Last fall I added peat moss, manure, and lime (to balance the pH of the peat) and I also grew winter rye which was turned into mulch in the spring. I've also been aggressively pruning and staking them which seems to work very well.
Other climbers are cucumbers, peas, and beans. Both of these were grown timed with other crops, the cucumber was planted as the peas were maturing and is now climbing their trellis, and the pole beans were planted over the edamame and are climbing as the soybeans are fruiting. (This was an accident, I thought the soybeans weren't growing so I planted some pole bean seeds I had then ended up with both.)
We usually do some kind of squash, either yellow (summer) or green (zucchini) because they're very prolific. They do take up a lot of space but the yield per square foot is very high- if you can avoid powdery mildew and slugs. The geraniums help repel slugs, and I also use iron phosphate (sold as Slug Magic or Sluggo) to control slugs and snails.
We're also trying some experimental crops this year. The 3 year old grew carrots at his school this year so he wanted to try some- they seem to be doing well, I wasn't sure if the soil was deep enough so we'll see what the roots look like when they're ready. Finally, we had a small crop of spinach in the spring then replaced it with cantaloupe. I've never done any melons or large things like pumpkins, so I don't know what will happen. I just read that you can train them to climb, but then need to put the melons in a net (like a piece of pantyhose) to support them. They need a ton of water and they also tend to attract rats and mice. That is not a good thing in a city garden, but they supposedly can be controlled with chicken wire (the larger rats, anyway.)
Finally, here's the first crop of the summer plants- 1 cucumber (they're the pickle sized variety, easier to eat the whole thing) and 3 zucchini (one of which ended up in the zucchini cake below.)
How does the cost of a garden compare to farmer's markets? It's hard to say- labor aside, I spend a lot on the garden. I haven't had much luck growing most things from seed- peas and carrots and beans are fine, but tomatoes and cucumbers and zucchini don't seem to work for me. So I buy those as seedlings, which is about $3 per tomato plant or per zucchini 6-pack (the above bush is all six grown together in a mound.) So plantings this year were about $25. We have bamboo stakes that have been used for many years, I just got some expensive permanent steel/plastic ones that will last a long time- say $10 per year on stakes, string, and cages. Then there's fertilizer, manure, peat moss, etc., which may be another $20 for the year. With the $5 garden fee, that's $60 total so far. So far we have 4 pickle cukes, 4 zucchini, only about 25 peas and a half pound of spinach (the early warm weather ruined the cold-loving crops, usually we have over 100 sugar snap peas.) At the end of the season we'll see how much we got for the $60 plus hours of planting, watering, and weeding.