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Watering: How Much and When? (most folks get the basics wrong . . .)

Improper watering is the top cause of plant stress and the number killer of houseplants.

Spring flowering bleeding hearts appreciate morning waterings.

Water needs vary dramatically depending on the type of plant, soil and location. Weather factors such as temperature, humidity and wind play a big part. It’s easy to see why getting the watering thing right can be a challenge. Here are some tips.


Water Deep

The goal of watering is to get moisture to the roots so it can be absorbed and used by the entire plant. Many gardeners stop watering when the soil surface becomes wet or when water starts to puddle or run off.  Often this approach wets only the top inch or so of soil, because water is absorbed slowly by heavy, dense and compacted soils. While the top is wet, down where the roots are (or where you want them to be) is still dry.

Check. Poke you finger, a trowel or a stick into the soil. Where is the moisture line?


Avoid Guessing

Each time you water, you want to apply enough to moisten the soil to the bottom of the root zone.

Water is measured in inches. Place an empty tuna or cat food can on the lawn or in the garden when the sprinklers are on. When the sprinklers stop, measure the water in the can. Now you know that your landscape is getting ½” or 1” per watering. No more guessing.

For most parts of the country, one inch of water per week is a good starting place. Modify this amount is your soil is sandy and drains quickly, or if you live in a dry, hot part of the country where moisture evaporates quickly.

Blue iris flower with water droplets in garden.

Watering outdoor plants early in the day is recommended.


When you water matters.

Watering early in the day, between dawn and 9am, is ideal as this allows plants to rehydrate before the sun bakes them. Evening watering leaves foliage wet and prone to fungus attack. For this reason, it’s not recommended.


Watering Pots, Windowboxes and Other Containers

First choose containers that have bottom drainage holes. This avoids having root-rotting water pool in the base of the pots.  Since the soil ball in most containers is pretty limited; it’s important that all gets wet when you water. Keep that watering can tipped until you see water draining from the bottom. If the container has a saucer, wait for all the water to drain through (10 – 15 minutes), and then empty the water from the saucer. This avoids standing water that can damage roots and provide breeding sites for mosquitoes. Should the drainage hole become block over time, poke a stick in the hole to loosen compacted soil.

If container soil gets very dry it may shrink and pull away from the container walls. Then when you water the moistures slips between the sides and soil, and right out the bottom. Watch for this and make sure all the soil is getting moisture. In extreme situations you may need to submerge the entire pot in a large tub to rehydrate the shrunken soil ball.

Mixed planing in coir lined container on fence.

Containers lined with coir fiber drain well so feel free to water generously.

Reevaluate as the Season Progresses

When temperatures are relatively cool, as in the spring, plants typically need less water. The same is true for little plants that don’t yet have much biomass to support. Tweak your watering plans as the weather gets hooter (or cooler) and as plants grow larger.







10/22/2013    Watering