Winterization
The last of the colored leaves are drifting from the branches, the nights are chilly, and daybreak seems too late in the morning. Sometimes winter starts in earnest in late October, and sometimes it doesn’t arrive until late December. By now, we would hope to have all of our winterization activities completed, even amidst the controversy over what those activities are exactly.
Starting with the lawn, if you have one, a treatment with a “winterizer” fertilizer should have happened a couple weeks ago. This is a low nitrogen food that helps the grass maintain good root structure and disease resistance through the winter months. Similarly, the trees and shrubs in your yard should have received a dose of phosphate and potassium, along with a boost of micronutrients and minerals, for the same purpose. Spring flowering plants such as forsythia and lilacs should get a high phosphate dose during monsoons to set good buds for spring.
This is also a great time to spread some mulch. Organic mulches will break down over the winter and provide food and protection for your trees, shrubs, and garden. In addition, mulch can provide a layer of insulation for the roots and help to prevent early, cool-season weed growth. A good thick layer of mulch can also help fruit trees stay dormant just a little longer in the spring to help protect against that late frost that usually nips the flower buds.
What kind of mulch is best? The kind that is good, inexpensive, works, and you will actually use. As I have said before, be careful about using too much of the chippings from the tree trimming companies. These are often loaded with allelopathic chemicals from the trees and even weed seeds. Allelopathic chemicals are natural substances many species of trees give off to prevent competition in their native habitats. They are chemicals that inhibit growth of other species, like all the cool stuff you are trying to grow in your yard. Bulk mulches are available at local materials yards and nurseries, and bagged mulch can be purchased just about anywhere.
What about the leaves that just fell from the trees? They’re free! Yes they are, and you can often find even more in your neighbors’ yards that they are more than happy to have you haul away for them. Be careful! Leaf litter under trees likely contains live insects, larvae, pupae, and eggs from critters that may not be advantageous to supporting what you are growing in your yard. It is best to compost the leaves and such and save that yummy stuff to apply in the spring or summer next year. Good composting should produce sufficient heat to kill most organisms, including bacteria and other unseens.
Irrigation? The on-going controversy continues. Inquiries and associated comments abound in online chat rooms. Shut it off, don’t shut it off. Drain it, don’t bother. Freeze protect it, take your chances. UGH! Here are some basics to help you decide. Our area generally has below freezing temperatures frequently throughout the winter, sometimes even single digits. The difference between here and some other areas of the country is it rarely stays below freezing for more than a few hours or a day or so. What this means is that the ground doesn’t usually freeze, and when it does, it doesn’t freeze very deep. So, if everything is buried below about six inches, it’s usually fine. Can it sometimes freeze deeper? Sure, but it’s rare anymore.
What about my above ground backflow prevention device? You better have someone shut it off and drain it, even if you have a cover. Unless this unit is in a heated box, it will likely freeze and the repairs can be costly. As for the rest of your system, freeze protection is not usually required provided your valves are below ground and protected. Often all that is needed is a chunk of insulation wrapped in a heavy garbage bag to keep it dry, stuffed into the irrigation box on top of the valves.
Drip irrigation does not need to be drained unless the main lines are above ground, and then only if the hard fittings are exposed and remain full of water. The hard fittings will indeed crack when water freezes inside them. The poly line is flexible enough to withstand some freezing without breaking. It is possible for water to freeze in the emitters and cause them to pop, but this usually happens when the system has been run the day before a hard freeze; watch the weather!
This brings us to the final point: watering in the winter. YES! Please water in the winter! How often? As a general rule, I try to water everything at least once a month if we have no precipitation. Keep in mind that an inch of moisture soaks in about a foot and a foot of snow produces about an inch of moisture. Most plant roots, including trees, are in the top 2-3 feet of the soil. Please, please, please, do not just leave the irrigation system the way the landscaper set it at the time of installation! This wastes a precious resource, does NOT water your mature plants effectively, and puts you at risk of problems in your landscape, not the least of which is root rot and the subsequent loss of valuable trees.
Hopefully, this clears up some of the confusion about what to do with the landscape in the winter.
See you in the frost!
The Horticoach