When it comes to watering your garden, you may have heard the phrase "an inch of water a week," whether it's from rainfall or irrigation. But what does that mean exactly? Do you stick your finger in the soil and feel how dry or moist the first inch is? Do you buy a moisture meter or rain gauge?
Experts say an inch of water generally equates to about six gallons per square yard, though this can vary depending on how well (or poorly) your soil retains moisture. This number also shifts dramatically depending on the time of year (your garden may need twice that amount in high summer), the amount of precipitation that falls in any given season, how well-established your plant's roots are, how densely you've planted and heavily you've mulched.
In general, you only need to water when the first four inches of soil are dry. If you don't have a moisture meter and don't want to keep digging holes every time you forget when the last watering was, use this trick: watch your garden for an indicator plant, which is the first plant to droop from thirst.
In a vegetable garden, this typically means plants with large, thin leaves like cucumbers, melons, and squash (as opposed to thick-leaved plants like cabbage, collards, and cauliflower). Those large leaves lose moisture fast and are an easy way to remind yourself when the garden is overdue for a drench.
Of course, you shouldn't wait for your plant's distress call every time; practice good watering habits (in accordance with your city's watering restrictions) by setting your irrigation on a timer and watering deeply but less frequently. Keep in mind that even the hardiest plants will droop in the harsh midday sun, but if they're healthy, they should perk up again by evening.