Carol O'Meara, Colorado State University Extension

Carol O’Meara, Colorado State University Extension

The wintry blast we’ve recently received should remind all gardeners that it’s time to plan for helping our gardens through a long, cold, dry winter. While it’s true we just had a wet storm and our plants got a nice drink of water, gardeners should think ahead on how to make sure your plants stay watered in winter.

The influx of moisture into the soil is good for the landscape, but for long-term success, keep track of our storms and set reminders to water your trees and shrubs if Mother Nature turns off the charm. Once every four weeks is the rule of thumb for assessing whether the weather brought an inch of moisture to the land.

To help trees and shrubs harden off for dormancy, we needed our landscapes to dry out a bit; having dialed back on irrigating in September and October was crucial to this process. But the soil can’t remain dry the entire winter or roots will dry and die, so sending the plants to bed with a long, deep drink ensures that, once the soil warms again, roots will be able to expand and resume its job of taking up water and nutrients.

The ideal time for that deep irrigation is once the leaves have fallen from the trees; both evergreens and deciduous woody plants benefit from it. Research has shown that this watering is the foundation for success in overwintering woody plants so it’s nice that Mother Nature sent the storm when she did.

Not so nice is the one she sent a few weeks ago, abruptly ending the warm fall and freezing leaves on their branches. Because we didn’t plunge into low temperatures and stay there, the plants should be fine. They need a series of cold events to signal that the time is nigh for settling into a winter’s nap.

Tuck them in with a blanket of mulch, approximately four inches deep – but don’t mulch all the way up to the trunk of trees. Creating a mulch volcano with a tree sticking out of it like a sacrificial offering in one way to offer your plant to the vole gods, who relish having a cover to hide under when gnawing on the bark.

Instead, take the mulch away from the trunk about 12-inches, then create a mulch ring around the plant.

When: Water once per month now through March if we don’t get an inch of water through snow or rain.

Make it easy: Measure snowfall at your house with a ruler; don’t rely on total accumulation listed in the news. Write each storm’s amount on your calendar and add it up every four weeks. If it’s less than 12 inches of snow, it’s time to water.

How: Warm days when temperatures are above 40 are best for watering. Choose days when no snow is on the ground and the soil isn’t frozen. In cold weather, water should be trickled slowly into the soil.

Make it easy: Coil a soaker hose so that it spirals out from around the tree and leave it there for use over the next few months. Long hoses can be used to water several trees of the same size at the same time. Have an inexpensive timer on the faucet automatically shut off the hoses, or set timers in the house to remind you to turn off water.

How much: Researchers are still working on this, but a good rule of thumb is to give your trees 10 gallons of water per diameter inch of trunk for them to survive.

Carol A. O’Meara is an Extension Agent – Horticulture Entomology at Colorado State University Extension Boulder County. For more information contact CSU Extension at the Boulder County Fairgrounds,
9595 Nelson Road, Box B, Longmont, 303.678.6377, e-mail comeara@bouldercounty.org or visit ext.colostate.edu/boulder.