Water before leaving. Chances are it’ll be hot when you’re away, so “make sure you give your plants a good soaking.” For established annuals and perennials planted in the ground, this should be enough to get them through a week. Move potted plants into the shade, and group them together if a friend will be watering them.
Consider mechanical aids. If you don’t want to spring for a programmable sprinkler, create a stand-in device using one-gallon milk jugs. “Dispose of the caps, cut off the bottoms, invert, and sink them” into the soil. Fill each one with water to give the nearest plant “a long slow drink.”
Weed, mulch, and stake. Pull weeds to keep them from thriving and add mulch to hold in moisture. Finally, “make sure tall plants are supported enough to account for added growth”—and possible storms.
Source: Portland Oregonian