Gardening: Brutal weather has weakened even the hardy plants

We are winding down what has been a crazy weather and gardening season. If some of you newer gardeners feel like the season was somewhat of a failure, rest assured even those of us who have gardened here for decades had major failures.

I have been asked several times why we lost so many supposedly hardy plants during last January’s cold snap and then through this summer’s heat. While these events resulted in damage, the damage was influenced by the culmination of long-term weather and drought conditions we’ve been experiencing for several years.

For starters, Eastern Washington has been in drought conditions since 2000. Over the past 10 years, the droughts seemed to have intensified, meaning plants are experiencing deeper and more frequent water stress. In this same time frame, our summers have been experiencing longer stretches of hot weather with a record high of 109 set in June 2021. The last two summers we have had month-long stretches of over 100-degree heat. The past two summers we’ve had long stretches of unrelenting heat. The high in my garden this summer was 108 degrees.

These conditions over time put a lot of physiological stress on plants. Most plants can adapt to changes over time, but some can’t and when they reach their limit, their health begins to decline. Often as gardeners, we won’t see this stress blatantly displayed. We will see it as subtle changes and then wonder why the plant died when we experience sudden extreme weather event.

Two years ago, our summer-like temperatures hung on to the end of October before winter arrived the first weekend in November. The warm temperatures kept the trees from starting their dormancy process so that few leaves had fallen. As a result, the leaves froze on the trees, bark and stems were damaged by expanding ice crystals in the plant cells. The same thing happened last fall but not to the same degree.

This year, there was no snow to provide insulation when we got our subzero cold snap in January. As a result, many hardy plants that were under stress couldn’t handle it and died or showed a lot of damage in the spring. Others took forever to begin growing. Even plants that did leaf out in the spring were still under so much stress that once our hot July weather hit, they couldn’t keep up and died.

What can we do about these types of conditions? In the short term, we can make sure plants go into late fall deeply watered. The recent rains have helped but may not be enough. It’s still warm enough to get a hose out and soak plants. Second, apply a 2- to 3-inch layer of shredded needles or leaves across your beds to insulate the ground. Put a foot of mulch over the crowns of plants like roses to protect the graft and the roots.

In the long term, if these weather conditions persist, we may have to consider growing different kinds of plants that can better handle the changing growing conditions.