This undated photo shows water leaving a watering can in New Paltz, N.Y. The amount of water in the watering can and the area over which that water spreads can tell you if you’ve watered enough, but not too much.
Gardeners often overestimate rainfall. A cloudburst might seem to have thoroughly saturated the ground, but scratch down an inch and you might find bone-dry soil.
Because watering — not too much and not too little — is one of the keys to a successful garden, it pays to be more analytical about that cloudburst.
The amount of rain that fell, how long to water your plants, or how much water plants need is often spoken of in terms of inches. As a general rule, plants need about 1 inch of water per week to really thrive. It’s easily measured with a rain gauge, which you can either buy or make at home out of nothing more than a coffee or some other can, and a ruler.
A rain gauge can tell you how long to use your sprinkler to put that inch of water onto the garden. Because the distribution of the water might not be uniform, set out a few cans at random over the area to be watered. Then turn on the spigot, and keep it on until the sprinklers have filled the cans with water 1 inch deep.
To cover an acre with water 1 inch deep requires about 27,000 gallons. On a garden of 150 square feet, an inch of water is equivalent to 90 gallons.
If you’re watering with a bucket or watering can, use the 1-inch measure to determine the amount needed for an individual plant. (It is especially important for newly planted trees and shrubs to be watered their first season.)
