Planting Edmonds is a monthly column written by and for local gardeners.
Recently, on a rare dry and sunny January day, I ventured out to my garden to see what was going on. I didn’t expect much – it’s January after all! – but I needed the fresh air. I was surprised and delighted to see many of the garden plants starting to grow; and some were even blooming.
While we are inside our heated homes, sipping coffee or tea, digesting our holiday gluttony, curled up with a warm blanket and reading a good book, our garden plants are outside. They are not only coping with the winter weather but thriving despite it! They seem to know that the end of winter is in sight and are getting a jump start on their full spring form.
That’s impressive. How do they cope with winter, and how do they know when it’s time to bud out, flower and germinate?
As we prepared for winter – getting out our warm clothes, putting an extra blanket on the bed, prepping some firewood, etc. – so did the plants in our garden. We can move to warmer conditions; our garden plants can’t.
As the weather gets colder, garden plants (except the annuals) prepare for dormancy by slowly hardening themselves for the winter weather ahead. Besides shedding unnecessary and cold-sensitive tissue, they make the remaining tissue more cold-tolerant.
Different plants have different strategies to survive a dark, wet Western Washington winter: the annuals don’t even try; they produce seeds and die. Perennials die back to reduce the exposure of tender tissue, such as leaves, to the cold, while their roots are insulated by the warmer confines of the soil. Deciduous trees and shrubs jettison their leaves, slow down their metabolism and hunker down for the winter as weather-resistant buds, stems and roots. You’ve got to admire our ubiquitous evergreens – they just tough it out leaves and all! This is an advantage because it means they have everything they need for a fast start when the weather warms up.
Most cold-weather damage to plants is caused by formation of ice crystals in the cells. These crystals pierce cell membranes, causing cell and tissue death. To prevent this horrible fate, plants increase the concentration of salts and sugars inside their cells to prepare for winter. This lowers the temperature at which ice crystals form for the same reason saltwater freezes at a lower temperature than fresh water.
In the middle of winter, most plants are in various degrees of dormancy. Their metabolism has slowed way down, they have more “antifreeze” in their cells and they are protected the best they can – thick scales on the buds, bark covering the stems and roots protected by the more hospitable soil environment. The roots don’t really stop growing. Plants still need water. In fact, dehydration is another way garden plants can be injured in the winter, through prolonged exposure to cold dry air. Luckily for us, Western Washington winters are reliably anything but dry!
Winter weather isn’t always consistent and predictable. There can be unusual periods of warmth followed by a return to freezing cold. It would be a bad thing for most plants to bud out and grow new shoots or flower during the teeth of winter. They would expend precious energy only to have that new growth killed by the return of cold weather.
To prevent this, some plants need a certain period of cold weather, called chill hours, before they break dormancy and flower. For example, apples typically need 1,000-1,400 hours of temperatures below 45 degrees. That is a long time and explains why Florida isn’t famous for its apple crop! The blueberry bush in my garden needs a modest 150 chilling hours. Not a problem in our climate! This chilling prevents them from flowering too soon and losing those tender blossoms. This is also why you dig up and store some bulbs, like tulips, in a cool sheltered environment over the winter, so they can experience their required cold period and then flower in the spring.
Our native plants have all of this figured out; they have evolved to grow optimally in our climate. When we plant non-natives, we must accept that they may not be a perfect fit for our climate. For example, when I lived in St. Louis, we had a beautiful magnolia tree outside the living room window. In a good year, it produced copious amounts of gorgeous large pink blossoms in early spring. The problem was, it wasn’t a particularly smart tree, in St. Louis anyway.
Many years, when we had an inevitable warm spell in January, that magnolia decided “Spring is here!” and tender blossoms burst forth from its protective bud scales. Then, inevitably, winter came roaring back and froze the blossoms. For the rest of spring, our magnolia tree was covered with drooping, brown petals. I used to yell at that tree “Not yet!” but to no avail. Meanwhile, plants native to the St. Louis region were still dormant, savvy enough not to fall for a spell of premature warmth.
Now, some rhododendrons ARE native to Western Washington, and other ornamental ones in our gardens come from parts of Asia with climates like ours. When I looked at my rhodies recently, I saw nice big flower buds covered with protective scales. As the weather warms, the buds will swell. They know to wait for spring to open and expose their gorgeous, but tender, blossoms – no yelling required.
To my delight, a couple of my garden plants are already flowering. The cool weather-loving primrose has taken advantage of our moderate weather this January to give us lovely blooms. And the sweet box currently has modest flowers, but what a divine scent!
When I moved to Edmonds from St. Louis over four years ago, I was stunned when I went outside to get some firewood in January and caught a whiff of floral heaven. In January? We traced it to these handsome evergreen shrubs growing next to the house. We looked them up and discovered the wonders of sweet box (Sarcococca confusa). Plants like primrose and sweet box that can grow and bloom this time of year are more cold-tolerant, obviously, than the winter-dormant ones. I am fortunate to have them gracing my winter garden.
Well, that brief spell of sunny warmish weather has gone, the cold rain has returned, and I am back in my house sipping hot chai. I see my winter garden in a different light now; it isn’t very flashy, but it is growing, surviving and I daresay thriving in subtle ways.
These clever plants have come up with ingenious ways to cope with winter weather. They sense their environment, prepare for winter and then, at just the right time (fingers crossed!), burst forth with glorious spring shoots, leaves and blossoms. I can’t wait. Until then, I will enjoy my primrose flowers, enchant my nostrils with the aroma of sweet box flowers, and watch my rhododendron buds slowly swell. I will continue reading books, sipping hot beverages and patiently wait for spring.
Joel Ream has been a member of Edmonds Floretum Garden Club since 2019. He grew up in Spokane and earned a Bachelor’s of Science in botany at the University of Washington and a Master’s in botany at Michigan State University. Joel spent 37 years as a plant biologist at Monsanto, using plant physiology, biochemistry and analytics to increase the efficiency of crop production. He also worked on new weed control technologies, regulatory studies to support the safety of new products, greenhouse and field evaluation of new crop varieties, increasing the nutritional value of animal feed and developing methods to measure grain composition. Joel retired to Edmonds in 2018.
Thank u for a joyful garden report. I am in Az for a while nice to hear my garden in Edmonds is probably ok.
Joel, thank you for telling me about Sweet Box.
I live in a condo with a small balcony but I do prize fragrant bulbs, bushes and plants.
I will take a chance on anything that delights that sense of fragrance!
Sky Nursery will be seeing me for a Sweet Box.
Great article. I never thought of winter weather and plants in this way. Thanks! So glad you moved to Edmonds.
Great article, lots of fascinating info and explanations about why plants behave the way they do. Thank you!
Thanks, Joel. Gardeners call sarcococca the official scent of the Northwest Flower and Garden Festival. It’s definitely a pick me up at this time of year.
Real first and last names — as well as city of residence — are required for all commenters.
This is so we can verify your identity before approving your comment.
By commenting here you agree to abide by our Code of Conduct. Please read our code at the bottom of this page before commenting.