Seedlings in pots and trays are hard to keep moist and require daily tending. Fortunately, growing transplants in little pots is not necessary because in autumn, when they’ll be set out, humidity is high, temperatures are cool, the sun is weak, and transpiration losses are minimal, so seedling transplants will tolerate considerable root loss. My nursery is sown in rows about 8 inches apart across a raised bed and thinned gradually to prevent crowding, because crowded seedlings are hard to dig out without damage. When the prediction of a few days of cloudy weather encourages transplanting, the seedlings are lifted with a large, sharp knife. If the fall rains are late and/or the crowded seedlings are getting leggy, a relatively small amount of irrigation will moisten the planting areas. Another light watering at transplanting time will almost certainly establish the seedlings quite successfully. And, finding room for these crops ceases to be a problem because fall transplants can be set out as a succession crop following hot weather vegetables such as squash, melons, cucumbers, tomatoes, potatoes, and beans.
Vegetables that must be heavily irrigated
(These crops are not suitable for dry gardens.)
Bulb Onions (for fall harvest)
Lettuce (summer and fall)
Radishes (summer and fall)
Scallions (for summer harvest)
How to Grow It with Less Irrigation: A—Z
First, a Word About Varieties
As recently as the 1930s, most American country folk still did not have running water. With water being hand-pumped and carried in buckets, and precious, their vegetable gardens had to be grown with a minimum of irrigation. In the otherwise well-watered East, one could routinely expect several consecutive weeks every summer without rain. In some drought years a hot, rainless month or longer could go by. So vegetable varieties were bred to grow through dry spells without loss, and traditional American vegetable gardens were designed to help them do so.
I began gardening in the early 1970s, just as the raised-bed method was being popularized. The latest books and magazine articles all agreed that raising vegetables in widely separated single rows was a foolish imitation of commercial farming, that commercial vegetables were arranged that way for ease of mechanical cultivation. Closely planted raised beds requiring hand cultivation were alleged to be far more productive and far more efficient users of irrigation because water wasn’t evaporating from bare soil.
I think this is more likely to be the truth: Old-fashioned gardens used low plant densities to survive inevitable spells of rainlessness. Looked at this way, widely separated vegetables in widely separated rows may be considered the more efficient users of water because they consume soil moisture that nature freely puts there. Only after, and if, these reserves are significantly depleted does the gardener have to irrigate. The end result is surprisingly more abundant than a modern gardener educated on intensive, raised-bed propaganda would think.