This is my third summer with a Square Foot Garden. Every year has been full of hope and promise but devoid of results. The premise of the square foot gardens is that with a high-quality soil blend, you can grow a lot of produce in small areas. The soil is theoretically so rich and abundant that you don't even need deep gardens. So 2 years ago I put out a lot of money to create 3 square gardens that hold 16 square feet each and to make a really fabulous soil blend with vermiculite, peat moss, and a bajillion kinds of compost. Each year it's started out well, but the plants never really take off and thrive. This year, soil tests showed that my garden was completely devoid of essential nutrients, so I've been fertilizing organically, but my garden is still doing what it always does--not much.
Take for example the zucchinis. Two plants from the same batch, planted at the same time. The one on the left is in the square foot garden, and just very recently started growing a little. Despite its tiny size, it has bloomed, but I've seen this other years. The tiny plants can't grow a proper squash, so it will get to be a few inches then go soft and rotten on the vine, never reaching a proper size. The one on the right was planted in a container bag into planting soil that I bought for $9.99 at the gardening store. The one on the right is flourishing and I have confidence that those blossoms will actually bear fruit.
Similarly, I have 4 tomato plants in the square foot garden, and one in a container bag. The ones in the garden on the left are tiny, with a few odd blossoms. The one in the container is huge and has set fruit.
In past years, I've had promising potato plants, but the harvest always turns out to be about the same number of potatoes as I planted. So again, the potatoes have been put into bags. The plants started out in 4" of soil at the bottom of the bags, and bit by bit I've added enough soil until the bags are full. No guarantees that I'll get a bigger harvest this year, but I hope so.
The square foot garden that formerly held potatoes has now become my onion and carrot garden. The onions are flourishing but the carrots aren't. I hope that under those huge green onion tops are delicious and oniony onions, but considering how my potato plants looked great but had not much under the soil, I'm not confident.
Conclusion: These shallow square feet gardens aren't as effective as the book promised. It's just not as easy as they say to get soil that's so fabulous it can grow good plants in tiny spaces. If I total up the cost of the building materials, the soil, and then all the fertilizers, composts, and worm castings I've purchased to try to get something to grow, it's embarrassing. It makes gardening look like a casual pursuit of the wealthy and privileged, rather than a frugal way to expand one's food budget. Sure, a lovely homegrown tomato is priceless, but I don't have limitless money to throw away on trying to grow one. I could have bought bushels of fabulous produce every summer at the farmer's market for a lot less money.