Answer: Each vegetable has varying requirements for spacing. I will give you the recommendations for each and then you can decide from there how to space the rows. If you double-dig your garden, i.e., loosen the soil down about 18 inches, you can move the plants closer together. For more information on this type of gardening, check out the references for "intensive gardening".
Beans, bush - 1-4 inches apart in rows 18-24 inches apart
Beans, pole - 4-6 inches apart in rows 30-36 inches apart
Cucumbers - thin seedlings to 12 inches apart - need a trellis to grow up on; Bush cucs should be planted in hills about two feet apart
Squash - this will vary depending on the type of squash you are planting. Most seed packets will tell you what the correct spacing is for the variety. Usually for vining squash, you should plant 2-3 seeds in each hill and allow at least six feet between hills.
Tomatoes - this depends on how you will be growing them. If you are growing in cages, allow at least a foot between cages for air circulation. Other training methods such as staking will require different spacing depending on the type of tomato.
I would definitely recommend getting hold of a good garden reference and also contacting your Cooperative Extension office for details on the specific vegetables you are growing.
Some great references: Gardening for Dummies by Michael MacCaskey (IDG Books, 1996) is a great, all-around reference book especially helpful for new gardeners.
Here are a few others to consider:
Rodale Press Garden Answers: Vegetables, Fruits and Herbs edited by Fern Marshall Bradley (Rodale Press, Emmaus, PA, 1995).
Step by Step Organic Vegetable Gardening. Shepherd Ogden, Harper Collins Publisher 1992.
How to Grow More Vegetables. John Jeavons, Ten Speed Press revised 1996.
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