Snoqualmie Valley Gardening: Preventing Winter Damage

This is the last guest post from the Snoqualmie Valley Master Gardener’s Association for 2012.  Look for more of their informative articles in February 2013.  Thank you to Kay Moreton for these great tips – and thank you to all the valley’s master gardeners for sharing their knowledge with Living Snoqualmie readers.

Rich Marriott, Meteorologist for KING 5 News recently reported that the end of 2012 could bring another El Niño winter to the Pacific Northwest.  “In Western Washington, that could result in a warmer and drier-than-normal fall and winter in the lowlands, with snow in the mountains through December.” Sounds lovely, but I wouldn’t count on it. Here in the Valley, our unpredictable winters can inflict considerable damage on our ornamental trees and shrubs, so do what you can now to minimize the harm while it’s dry and we have moderate temperatures. Here are some suggestions:


  1. Do not fertilize or heavily prune plants late in the fall; it stimulates new growth which is susceptible to freezing temperatures. However, September/early October is a good time to fertilize your lawn to promote root growth.
  2. Cover bare garden soil with mulch or plant a cover crop to protect the soil from compaction, erosion and nutrients leaching from heavy winter rains. Mulch can be in the form of compost or any grade of bark. If it’s not windy in your area, leaving the fallen leaves in the garden beds (not on lawns though) is excellent mulch.
  3. If you over-winter plants in containers, move them to sheltered areas in the next month or so. To prevent the plant roots from freezing, wrap containers in bubble wrap or old rugs and move them under the eaves on the sheltered side of the house. You can move tender plants to the garage especially during very cold temperatures.
  4. Keep plants watered during long, cold dry spells; especially containers or plants under eaves or overhangs that don’t get rainwater or snow. A good drink once a month is about right.
  5. Walk around your garden and look for shrubs and trees that have broken, diseased or dead branches that might cause more damage if we get a snowstorm or high winds.  Remove these branches now. If in doubt about a particular tree, consult a professional.  You can find an arborist through Plant Amnesty – – or the PNW International Society of Arboriculture –
  6. Fall is an excellent time to plant new trees and shrubs, but do your homework before purchasing plants for your yard. Go to the USDA Zone map –, type in your zip code and get a description of your zone. Select plants that will grow successfully in your climate. Regional and local plant societies also have lots of good information on which plant varieties grow well here and how to care for them. Here are a few of the those societies’ websites:


Hopefully, Rich Marriott is right in his prediction of a nice warm, dry winter.  Lavenders, hebes and rosemary plants (marginally winter hardy) will survive to bloom again. But if the inevitable happens and you’re faced with plants that didn’t make it through the winter, don’t look at the result as a catastrophe, rather as an opportunity to plant something new and different. Perhaps one of those gorgeous new heucheras (coral bells) that are very cold hardy! And, to ensure blooms next spring, plant daffodil bulbs now – they LOVE the cold!


Our plant clinics have ended for the season, however information can be found at the Snoqualmie Valley Master Gardeners’ website at


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