rinda's blog

One of the hardest questions I have to answer is, 'How long should I water?' Partly that's because different plants have different watering needs, and partly, of course, because different methods of irrigation yield different amounts of water.

The rule of thumb is to water an inch a week. If it's rained, of course, you need to water less. If you have new plantings, more. But for established gardens, an inch of water is best.

It's also better to give the plants one or two serious dousings a week, rather than daily dribbles. The idea is to get the water deep into the soil so the plants have to send their roots down and out in order to find water. This lets the roots stabilize the plant and gives the plant more access to nutrients.

So how do you know how much is an inch? It's pretty simple: put a can or measuring cup in the garden. It's best if you sink it to ground level, so you can measure accurately how much water actually reaches the soil. If you're using a sprinkler system, run it until you have an inch of water in the can, and then you'll know how long you need it to go to reach the one inch goal. If you have a drip system, sink the can into the soil by the soaker hose and do the same thing - run the system until you get an inch of water in the can. Then you know how long it needs to run each week. You can set your system to run twice a week and your plants will be much happier. If you don't know how to set your irrigation system, call the company that installed it, or call me, and learn how to manage it.

It can't hurt to leave the can in the soil so you can check how much rain the garden's received too.

If you're watering by hand, it's even more important that you find out how long it takes to reach an inch, since watering by hand is usually the culprit in an underwatered garden. You stand there, la-la-la, water, water, water, and then it looks like the soil is moist, so you move on. But how deeply did the water penetrate? Again, get out a can, put it on the ground, and stand there with your hose.

When you water too much, especially if your soil is heavy on clay, the water sits in the soil and the roots can get waterlogged, lack oxygen, and sicken or die. Probably more people err on the side of overwatering than underwatering (especially since the plants will tell you when they're thirsty). There's no need to run sprinklers every day, nor does your lawn need water every day. In fact, grass is like other plants in that it develops better roots if it gets to dry out between watering. And in August, just let it get brown. It'll come back in fall, and you'll be the water-conserving eco-hero on your block.

There are plants that want a lot of water and others that don't need much. If I put in a garden for you, I'll be grouping those plants together so you'll have a high-water and a low-water zone. Mostly I try not to use many high water needin' plants unless you have a part of your yard where water collects, and then we can talk about a rain garden.

All plants need consistent water in their first season. After that, most trees and shrubs can get by with very little extra water. One way to tell if your perennial garden needs water is to look closely at the plants' leaves. If they are limp, they most likely need water. The plants are not going to die if they get thirsty, but do pay attention to them and water when they look parched.

In the fall, it's good to keep watering plants, especially evergreens, until we get a hard frost. Because evergreens stay, um, ever green, they continue to breathe. Plants breathe in carbon dioxide and breathe out water (one of the reasons we need them so much), but like us, they also breathe out water vapor. That means they're losing water all winter, and if we don't get much snow, they can be damaged. After we have a frost, you can put ice cubes around the base of the plant. The ice will melt when the weather warms up and the plant will get some needed water.

When in doubt, use the human digital test: stick your finger an inch down into the soil. If it's bone dry, water. If it's moist below the soil surface, wait. If you don't want to mess up your manicure, dig down a bit with a trowel and then check the moisture.

And don't forget to drink water yourself!