By Dot Zanotti Ingels
As I write this it has finally started to rain in Marin. Hooray!
I wanted to share some guidelines for winter watering of your trees and shrubs if the season is unseasonably dry as this one has been. Most of us ignore our landscapes when the weather gets cold and we turn off our irrigation systems. For our trees to survive the winter and stay healthy they need to have moisture. Even when the trees are dormant they need water, especially if they are young (under five-years-old) landscape trees and do not have an extensive root system to count on.
The water absorbing roots of trees are located mostly in the top foot and a half of soil, where they find plentiful oxygen and moisture. If the soil dries out too much these smaller roots dry up and die. In the spring, the water-stressed tree has difficulty emerging from dormancy until more fine roots can be produced to find water.
Generally speaking, we are told not to water oaks. The reality is a little more complicated. In drought years, it doesn’t hurt to give your oak a deep soaking once or twice during the late spring and/or early summer. Exactly how much water and how often depends on a lot of factors, including the soil type, drainage, and the oak species. However, installing sprinkler irrigation under established oaks is almost always a bad idea. Call us if you want more specific information about your oak trees and drought.
So what to do? If there has not been at least a half-inch of rain in a three to four week period, water your trees even in the winter. Apply enough water to soak at least eight inches deep into the soil. The majority of a tree’s water absorption system is at and beyond the drip line, so that is where you need to water. Only water at the trunk for a newly planted tree.
If you have any questions about winter watering or any other horticultural issue, contact the Marin Master Gardener Help Desk. We’re available Monday through Friday, 9 a.m. to noon, and 1 to 4 p.m.: UCCE Master Gardener Desk, 1682 Novato Blvd., Suite 150B, Novato, CA or call us at (415) 473-4204.
You can also check out our quarterly newsletter, The Leaflet, online. The winter edition is just out and is full of timely information, such as protecting your garden from frost, selecting a fruit tree and brightening your winter garden. You can subscribe to the newsletter so you do not miss any of what the Marin Master Gardeners are up to and have to share.
UPCOMING CLASSES BEING GIVEN BY THE MARIN MASTER GARDENERS
February 1: at 10 a.m. -- Landmark Society, 841 Tiburon Blvd., Tiburon. "What's Lurking in your Winter Garden" with Lois Stevens.
February 8: at 2 p.m. -- Inverness Garden Club, Gables Library, Inverness. "Backyard Composting" with Joan Irwin.
February 25: at 11 a.m. -- Novato Library, 1720 Novato Blvd. "A Garden on Your Patio" with Jean Sugiyama.
February 29: at noon -- Marin Civic Center Library. "Container Gardening Made Easy" with Sherry Rogers.
March 7: at 10 a.m. -- Landmark Society, 841 Tiburon Blvd., Tiburon. "Container Gardening Made Easy" with Sherry Rogers.
April 6: at noon -- Marin Civic Center, Supervisors Chambers, 3501 Civic Center Drive. "Growing Great Tomatoes" with Jean Sugiyama.
April 4: at 10 a.m. -- Landmark Society, 841 Tiburon Blvd., Tiburon. "Habitat Gardening" with Dave Phelps.
April 20: at noon -- Marin Civic Center Library, 3501 Civic Center Drive, San Rafael. "Bees of Marin" with Glenn Smith.
April 28: at 10 a.m. -- Tamalpais Valley Service District, Tamalpais Valley Community Center, 305 Bell Ave., Mill Valley. "Backyard Composting" with Joan Irwin