Square foot gardening is most often used for growing veggies, herbs and greens in a small space.
The homegrown version of the common globe onion is not onions need fertile, carefully worked, moist soil with good drainage. Bush green beans will produce quite well in a relatively small i grow them on large square fold out tomato cages. Salad greens are really easy to grow from seed and you could definitely still start them now. Larger crops, like the cabbage family can be planted in a square foot bed but remember they will need a lot of room!
