Winter gardens are common in the Pacific Northwest. Our winters can be so mild that plants seem to grow all year long.
But this is deceptive. Even when we don’t see the heavy and frequent snows of last year, winter poses risks for the garden. In fact, a covering of snow can provide insulation for plants and protect them from freezing.
Frost and sodden ground are the most common plant killers in our region.
The greatest danger to plant survival is a sudden freeze after a warm period. A plant that has not gone dormant has no defenses against winter kill.
We are going to look at ways to protect your outdoor plants and containers from the cold in a series of posts. Today, we’ll talk about frost.
FROST – PRETTY BUT DEADLY
Around Seattle, our first frost usually occurs in early November and our last frost happens in late March. (These dates are only approximate, and there are microclimates all around Puget Sound with different date ranges.) Young, tender plants, growing plants, and new buds are most suceptible to the cold – so you won’t be suprised to learn that the worst frost damage happens to plants in the fall and spring. During the depths of winter, plants are dormant and better able to weather the cold temperatures.
Our almost constant cloud cover throughout the fall and winter helps to moderate temperature swings between day and night and protects our plants. Surprisingly, it is the beautiful clear days, with sunny, blue skies that bring frosty nights.
There is no way to avoid frost. Even if we could prevent sunny days in winter, we wouldn’t want to! But we can minimize the damage.
- Frost damages plants by drawing moisture from the leaves to form the ice crystals. Dehydrated plants suffer the most severe injury, so don’t let plants go completely dry during sunny weather.
- Bare, dry ground loses heat much more quickly than ground covered with mulch. Although our frosts rarely freeze more than the top inch or two of soil, protect your plants’ roots with a good covering of mulch.
- Do nothing to encourage new growth. Don’t fertilize. Don’t prune plants in the late fall – wait until late spring, when the last killing frost is past.
- Don’t over-protect your plants. Plants need to be “hardened off” to survive the winter. As temperatures drop and daylength shortens, your plants will slowly go dormant. Don’t interfere with this cycle for cold hardy plants.
- Container-grown tender perennials can often be over-wintered by placing them in an unheated garage. Remember – you aren’t trying to keep them blooming year round; you just want to protect tender plants from winter kill. Allow them to go dormant, but don’t let the soil dry out completely.
Despite your planning and best efforts, some plants will inevitably suffer frost damage. Sometimes foliage will die back completely. The plant may appear dead, only to push up new growth from the roots in the spring. That is why it is so important to protect the roots from freezing – the topic we will look at next.
This post was Part 1 of a series.
Part 2: Frozen ground
Part 3: Protect Your Pots
Photo by KaCey97007 Released under Creative Commons License