I've had a couple smaller backyard gardens for the last few years. Based on my experience and not knowing your climate, I would suggest staying away from vegetables that need a lot of spacing between them. I made that mistake with Corn one year.
I ended up using a good portion of my garden and only produced 8 ears of corn. I've had good success and amount from Carrots, Tomatoes, Green Beans and Peas. My first year with a backyard garden I grew zucchini.
I ended up with so many of them, I gave most of them away. I've never really done anything to prepare the soil, other than turn it over each year and remove weeds as the start to grow.
Check out All-New Square Foot Gardening and the website squarefootgardening.com. The site has a forum and I know rooftop gardens have been one of the subjects. You can grow much less in a smaller space with this method.
The important factors are going to be your climate and the amount of sun. You can trellis many vegetables including tomatoes and squash to save space.
Naturally, the ideal plants would be those that take up the least amount of room. Pole beans, cucumbers, or peas that tend to vine upwards would be good as long as there is something provided that they can climb. Green onions, beets,radishes, carrots, celery; or turnips will not take up much room.
When choosing vegetables, look for "tiny," "miniature," or "dwarf" in the name of the plant. Tomatos will grow well, but they also need cages or get your uncle some Topsy-Turvy's. Then he can hang his tomatoes and use that area for something else (the same applies for beans or peppers).
Leaf lettuce is a good choice as well as spinach. Make sure the soil is tilled properly. Add some "Miracle Grow" soil or soil enhancer to make sure the soil is healthy enough to produce great tasting veggies.
The plants will need regular watering. Especially if he gets the Topsy-Turvy's. Relying on just rain is not enough.
Weeding is essential as well.
He might try a Square Foot Gardening approach where he builds up and improves the soil in a small area. He can take a soil sample to his local County Extension Agent to determine what the soil might be lacking and learn what is the best fertilizer for the plants he decides to grow. A picture of a square foot garden is included.
There are books available on the topic which should be able to be found at the library. I have grown vegetables in small areas like this and find tomatoes, onions, peppers and herbs all do well. Sometimes vineline veggies like cucumber are harder because they grow out of the space you have.
For your small garden you could choose the following vegetables: • Tomato • Sweet pepper • Carrot • Climbing beans.
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