When to Water

In some cases, a sprinkler is the best option for watering a large area. However, only 40% of the water reaches the root zone. For more efficient watering, install a soaker hose early in the season, before the plants get big.

A friend of mine once had a summer job working at one New England's premier nurseries. He told me that the nursery owner always had his new employees spend their first two weeks doing nothing but watering plants. By teaching his staff how to properly water a plant, the owner was ensuring the health and vitality of his inventory. But he also used this initiation period to find his best employees: people who paid attention.

The key to properly watering plants is all about paying attention. That's because there are no hard or fast rules. Determining whether a plant needs water or not is always a judgment call. It depends on the type of plant, the type of soil, the weather and exposure, the time of year, and many other variables.

Every plant in your house or garden is probably unique in its water requirements. The only way you can accurately determine if you do or don't need to water, and how much water to apply, is by assessing the needs that particular plant. Fortunately this is easy to do — even for a teenager on a hot summer day. You just need to check the soil.

Get a feel for the weight of a well-watered hanging basket by lifting it.

If you're working in a nursery, the right way to do this is to lift each and every pot before you water. Over time, you get to know how heavy a pot should feel if all the soil inside the pot is consistently moist. If it is, you don't water. If it's not, you water slowly until all the soil in the pot is moist and water is running out the bottom. Then you lift the pot again to check that it feels right.

Watering is of no value if the water runs down the outside of the root ball, leaving the roots at the core of the plant dry. The point is to ensure that the soil at the core of the pot—where the plant's roots are located—is thoroughly moist. This is important to remember in the greenhouse when you're watering seedlings, in the house when you're watering houseplants, in the garden when you're watering your tomatoes, and in the landscape when you're watering shrubs and trees.

You can't use the "lift" test to evaluate whether or not the plants in your garden or landscape need water, but you can occasionally dig down 6 or 12 inches and see what's happening down there. A soil core sampler is perfect for this job, or you can just insert a sharp spade and then pull on it back to reveal a picture of what's going on down there. If the soil contains some moisture down to a depth of 6 or 12 inches, you're in good shape. If the soil in direct contact with the roots is bone dry, it's time water!

A few more tips and techniques for proper watering:

• Focus on the root zone. Remember that it's the roots that need access to water, not the leaves. Wetting the foliage is a waste of water and can promote the spread of disease.
• Water only when needed. Water timers are a great invention, but you should not be automatically watering your lawn and garden, regardless of the weather. Too much water can be just as damaging to plants as too little water.
• Water deeply and thoroughly. Lawns and annuals concentrate their roots in the top 6 inches of soil; for perennials, shrubs and trees, it's the top 12 inches. In some cases, it may take hours to get moisture down to a depth of 6-12 inches.
• Water in the morning. If you do get moisture on the leaves, this gives them time to dry out. It's much more difficult for plant diseases to get a foothold when the foliage is wet.
• Mulch everything. Mulch reduces surface runoff and slows evaporation from the soil surface.
• Use the right tool. When you use a sprinkler on your lawn or garden, only about 40% of the water actually reaches the root zone. Instead, try to apply water directly to the soil surface and apply it slowly so it soaks in, rather than runs off. You can do this most effectively with an open-ended hose at half-pressure, a watering can without the rose, or a soaker hose.