Snow in Portland Landscapes

Hellebores - one of the horticultural joys of winter!

Hellebores - one of the horticultural joys of winter!

What to keep in mind in Portland when it snows?

In this post I’d like to explain several key things to know about what snow and freezing temperatures can do to your landscape, and how to prevent major problems. If you have any Arborvitae in your landscape, you will definitely want to read number 4!

There is often a week or so of snow here in the Portland, Oregon area, and residents are usually giddy and/or confounded by it. Hardy plants are unaffected in the long run, and many plants actually need a certain number of freezing hours to flower or fruit at their best!

But the following are critical things to be aware of when it comes to snow and your landscape:

  1. Snow and freezing temperatures make many plants temporarily brittle
    Winter is the best time to prune many shrubs and small trees, but not when they’re frozen. Even just rubbing up against a plant when it’s frozen can cause that branch to break or even just shatter slightly, causing permanent damage to the tissue. One exception to the rule are many conifer varieties, which are not made as brittle as other plants.

  2. Irrigation system components can freeze and be severely damaged
    Winterizing your system is usually very important (draining or blowing out the pipes, and preparing the back flow device). Even though most irrigation piping is underground quite a few inches, certain sections are often more shallow than you think, and a sustained frost will penetrate the soil quite a few inches. Many brands of above ground drip tubing can be damaged by heavy frost. And your back flow/anti-siphon device can crack or shear in heavier frost (under 28 degrees especially) if it’s not prepared properly for winter.

    Many systems in Portland will seemingly do fine for several winters even without winterization, but damage can be cumulative until something finally ruptures, especially with metal products like a back flow device. These cost many hundreds or thousands to replace; winterizing your irrigation system is a cheap insurance policy!

  3. Don’t walk on frozen grass if you can help it!
    I’m sure you’ve noted that spinach and other leafy vegetables turn darker and wilt once frozen. This is because the process of freezing collapses or ruptures the cell walls, much like cooking. Living grass and turf can withstand the snow and ice by themselves, but once stepped on, the cell walls will rupture in the grass blades and either kill or seriously damage that section of turf. It also tends to create unsightly depressions and long lasting foot prints in the soil.

  4. Snow can be the kiss of death for your old, great Arborvitae hedge if you don’t take action

    As a landscaping company we’ve worked on hundreds of Arborvitae hedges, some over 80 years old. Nothing damages Arborvitae like heavy snow. We’ve seen decades old, perfect hedges aesthetically destroyed by the heavy snow and ice events we’ve had over the last several years. Heavy snow doesn’t happen every year in Portland, but when it does it wreaks havoc on plants that aren’t used to it.

    The key to prevent this is to get out there and knock or blow the snow off before it has a chance to put sustained pressure on the branches, drooping them permanently and creating dead zones! Once snow and heavy ice has sagged an Arborvitae branch down for more than 24 hours, it is usually too late.

Keep these things in mind and enjoy the snow (and crazy drivers) while it lasts!