December Gardening Tips for the Pacific Northwest

Gardening slows outdoors in Northwestern gardens in December. But there's still garden fun to be had indoors and out.


    Long-lasting Christmas Trees

    Not sure how to keep your natural tree soft and green? Start by choosing a fresh tree.

    • Check its needles. On a moist tree, the needles will bend in your fingers; on a dry tree, the needles will snap. Dried out trees lose their needles easily. If you gently grasp a branch and pull on a dry tree, you'll end up with a handful of needles.
    • Cut 1-2 inches off the trunk base when you get the tree home. Store it outside in water until you're ready to decorate. Check the tree stand twice daily to ensure water levels remain constant.
    • Needles will dry out more slowly if you spray them with an antidesiccant product. This applies to fresh garlands and wreaths, too. Also, the warmer the room is where your tree is stored, the faster it will dry out. Try to keep your tree away from fireplaces, heating vents, and other sources of warm air.
    • After the holidays, clip branches from the tree and lay them over planting beds for winter mulch. The boughs provide ideal protection for garden plantings.

    Get more tips for picking a perfect Christmas tree.

    Find the best type of Christmas tree for you.

    Test Garden Tip: If you remove lower branches from your tree, use them to decorate other areas of your home, inside or out. Indoors, protect wood finishes by placing boughs on a piece of fabric or parchment.

    Beat the Cold

    Outwit winter chill by preparing for cold snaps. A few simple steps can mean the difference between a plant that dies or survives.

    • If a frost warning is issued, water plants before temperatures drop. Plants that are well-watered survive frost better. When frost comes without warning, watering afterwards helps plants survive. Irrigate after plants start to thaw.
    • When you're covering plants for the night, ensure your protective coverings touch the ground. Frost protection covers work by trapping radiant heat in soil. As soil releases its heat, the cover holds the heat around the plant. Use fabric covers, such as plant insulating blankets, burlap, or bed sheets.
    • It's easy and quick to build a shelter around tender plants: Anchor stakes in soil and attach a cover to stakes.
    • Not all plants can withstand the same low temperatures. If temperatures are predicted to drop below 25 degrees F, protect pittosporum, fragrant daphne, and waxleaf privet. If temperatures are predicted to drop below 15 degrees F, protect broadleaf evergreens such as rhododendron, camellia, holly, etc.

    Test Garden Tip: When a lawn is frozen or grass blades are frost-covered, keep off. Walking on lawns in this condition can actually damage turf crowns.

    Plant for Winter Color

    Dress up winter pots, empty vegetable gardens, and flowerbeds with cheerful flowering annuals. Pansies, snapdragon, dianthus, calendula, and viola will stage a pretty show all winter. You can also rely on flowering cabbage and kale to brighten winter scenes.

    Tuck a dose of slow-release fertilizer beneath root balls as you plant these colorful beauties to ensure they're well-fed throughout the season.

    Add a touch of green indoors by filling a sunny windowsill with potted herbs. Choose varieties you cook with to make the best use of them.

    Planting Trees and Shrubs

    Look for bare-root trees at nurseries this month. These soil-free gems offer a tremendous bargain; they'll take off quickly in cooler winter growing conditions.

    If you plant balled-and-burlapped plants, don't use the trunk as a handle to move the plant. Each time you do this, you risk dislodging soil from around roots. It's best to handle the plant by the soil ball.

    This is an ideal time to plant dormant trees and shrubs, as well. Consider colorful bloomers like mock orange, hydrangea, spirea, or flowering quince.

    More tips on properly planting your tree.

    Planting Bulbs in December

    If you still have spring-blooming bulbs on hand, get them in the ground as soon as possible. Feel free to scoop up clearance bulbs. Compost any that are soft or dried up.

    Planting tips for bulbs.

    Pacific Northwest Garden Tasks

    Go on rodent patrol: It's prime season for pesky varmints to chew bark off trees and shrubs. Eliminate hiding places for rodents by removing weeds around woody landscape plants. Also, never pile mulch directly against a tree trunk or shrub base.

    Keep compost going: Heavy winter rains can quickly drench compost, eliminating oxygen from the pile and making it stink. Slip a cover over your compost during winter's rainy season. Blanketing the top is fine.

    Monitor water flow: During heavy rainfalls, observe water runoff patterns in your landscape. Address these issues next year with ditches or French drains. Or spend winter learning about rain gardens and bioswales -- and add one of these gardens to your yard.

    Store tender roots: Before the month ends, examine roots, tubers, and corms you dug during fall. Compost any that are soft or moldy. On dahlias, cut out bad spots and dust the wound with sulfur. Remove these tubers from the others and store separately.

    Stop hitchhikers: Reduce home insect invasions from firewood by bringing in only enough wood to burn for a day. Knock logs together or against the ground before bringing indoors to dislodge insects.

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