More information. Hey what can I say, we can talk about this subject for days and still not cover it all.
You must understand that one person can only eat so much. For instance on tomato bush can provide tomatoes out the yang yang for one person. A family of three does not need 12 tomato bushes – even if you are planning on caning tomatoes for the rest of your life.
Things like leaf lettuce can, through conservative harvesting methods (picking a leaf here and there off of several plants as needed) will continue to produce through its growing season. I usually have 2 of each type of leafy green (spinach, lettuce varieties) that I harvest the day before (to chill it) I use. I’m the only one who eats leafy greens here – 6 to 8 plants is far much more than I can eat even when eating a salad each day. The landlord, the parents and a few other people get gifts of vegetables – oh they smile and take it, but I have a feeling I need more friends in order to spread out the wealth of produce

.
Zucchini, summer Squash and other things are prolific producers – if you harvest before the fruit is fully grown. Most folk prefer a zucchini that is small (4-6 inches long) however the fruit grows over a foot long when mature. Zucchini bread (muffins, blah) is best out of a mature zucchini, zucchini as a side dish is best as a young, tender squash. One plant can produce more zucchini that 2 people can eat.
Beans like green beans can produce for a long time; again you don’t need that many plants to feed your family beans – unless your family loves beans

. To extend the growing season I take one packet of seeds, planting new seeds every other week. As one plant reaches the end of its production, another plant is just starting, and so on. I do that with carrots and peppers too.
Radishes, carrots, onion will require more plants, not necessarily more room. Think how many onions do you actually need or use? Even if you are drying onions you don’t need that many – same applies to garlic, carrots, radishes, etc. Many herbs are perennial and produce much more than you will use. Some will take over, like mint – pesky plant will take over your garden. Its best used in pots, or placed in a corner of you yard where you can mow around it each week. Mowing mint rewards you with that minty smell

Corn is a bad family garden choice. You figure 2-3 ears of corn per plant, each plant needs at least a foot of space, that adds up to a lot of plants. Besides corn is hard on soil, it needs lots of nitrogen’s, and is fairly intensive in the care department.
Potato is an iffy crop. We do crow potato, but not like they do in Idaho or Ireland, instead of burying potato cuttings in the soil, I lay them on the soil and cover with mulch. In more recent years I have a 4’ diameter wire cage where I lay the potato on about 1 foot of mulch, cover in about 6 inches of mulch and as the potatoes grow I add mulch to the bin causing the potato to grow upwards. When the season is over I pull the cage, rake through the mulch and harvest the potatoes. The cage is about 3 foot tall.
Old methods tend to require far much more land, causing the potato to spread outward, instead of upward.
Two years ago I put the potato cage on a spot of lawn where I wanted to plant another rose bush. At the end of the year, after harvesting the potatoes and putting the mulch in the compost area I had an area 4 feet in diameter where the grass was gone – turning the soil (leaving behind semi-composted material) and digging my holes I was able to plant my 3 rose bushes – laying in a layer of mulch to prevent weed/grass from growing, adding a bit of backer board as a trim.
Number of plants for a family of four:
http://www.humeseeds.com/seedneed.htm Of course if only one person eats turnips you would cut the number of plants to reflect such.
Unfortunately this chart doesn’t give number of plants; it gives you a row of X feet in one column, the spacing in another. Personally I plant turnips 3 to 4 inches apart thus the row described is not matching my needs. For turnips as example, it comes down to 15 feet divided by 6 inches (15’ = 180 inches/ 6 = 30 plants for 4 people/ 4 for 7.5 plants per people – round up to 8) However I think one person can eat more than just 8 turnips – I personally love turnips and plant about 20 of them, over a period of time so I don’t have all 20 ready to harvest at once.
Their example of peas strikes me as wrong, I have a 5 foot section which grows on trellis and we have more peas than we need – plus I parch and freeze some. Pease are short lived, thus planting a series spaced a week apart will produce a steady harvest over time.
There are hundreds of varieties of vegetables, mostly hybrid plants. I personally prefer old fashioned or “heirloom” varieties which breed true. Seed propagation is a little more work, for instance carrot will mate with Queen Anne’s Lace – the trick to raising carrot seed in a place where Queen Anne’s lace grows wild is to plant your seed crop at a time where the carrot and queen Anne’s is not blooming at the same time. Squashes (pumpkin and acorn as example) will cross pollinate. This can lead to “interesting” squash the next time you plant. Once year my field pumpkin (Used for cooking, unlike Jack O’lanterns which are thinner shelled, larger and used for carving) breed with gourds – I ended up with a touch shelled pumpkin which tasted “different” than just pumpkin – nearly impossible to cut into. Now I isolate the flowers in a breathing plastic bag (one with micro holes to allow moisture and heat to escape) and pollinate by hand (rubbing Q-tips in one flower, then the next, and the next).
Most, not all, of my vegetables I propagate myself now days.