December Gardening Tips for the Desert Southwest
Outdoor Holiday Decor
When stringing holiday lights outdoors on landscape plantings, wrap the plants lightly. Remove them as soon as possible after the holiday passes. Avoid covering upright cacti with materials that don't permit light to reach stems.
Count on cool-season annuals to add color to the landscape. Plants such as pansies and violas, snapdragons, flowering stocks, calendulas, and sweet alyssums will flower all winter at lower elevations.
Fill outdoor containers with clippings from the local landscape. Choose stems with fruits or berries, needle evergreens, hollies, or other plants with strong winter interest.
At lower elevations, watch for colorful blooms on firecracker penstemon, cascalote, jojoba, desert marigold, and chuparosa. These are great plants to add to your landscape for December color.
At higher elevations, the most reliable blossoms are flowering indoors, including amaryllis and paperwhite bulbs, along with traditional holiday plants. As winter settles in, take time to inspect your landscape. Look for bare spots and areas that might benefit from an ornamental grass or sculptural yucca. Mark the spot and add plants after the New Year.
December Garden Chores
Frost: Cold weather typically arrives in full force about midmonth at lower elevations. Shift potted frost-sensitive plants under cover. When frost is forecast, wrap tender landscape plants with burlap or horticultural frost blankets.
Pruning: Grab your loppers and pruners and tackle deciduous trees. Candidates include chaste tree, desert willow, and catclaw acacia. Hold off on pruning palo verde, mesquite, or plants damaged by frost. Wait until new growth emerges in spring before removing freeze-damaged wood.
Weeds: As winter rains arrive, weeds start sprouting at lower elevations. Try to keep up with weeding by hand pulling or using a hoe on tiny seedlings. If rains have begun but weeds aren't up, apply a preemergent herbicide to interrupt weed seed germination.
- At higher elevations, deeply water landscape plantings once this month.
- At lower elevations, water once or twice this month.
- Do not water established xeriscape plantings.
- Water winter-dormant container plants monthly or less.
- Water actively growing container plants weekly or more frequently if soil dries.
- Water wildflower seedlings every two weeks if rainfall is scarce.
How deep is deep enough for irrigation? Apply water to soak soil:
- 3 feet for trees
- 2 feet for shrubs
- 1 foot for annuals, herbaceous perennials, groundcovers, and vines
- 8-12 inches for vegetables and herbs
Lower Elevation Planting
There's a lot you can plant in December at warmer, lower elevations. Now's the time to get herbs and vegetables in the ground, including lettuces, cauliflower, kohlrabi, cabbage, borage, feverfew, chamomile, calendula, beet, mustard greens, radish, spinach, and carrot. Plant seeds of these herbs: chervil, dill, fennel, parsley, and cilantro.
Test Garden Tip: Watch for aphids on new growth. Before blasting aphids off plants with a strong spray of water, look for beneficial insects. You don't want to blast those away.
Enjoy a Natural Christmas Tree
Celebrate the holiday season in natural style with a freshly cut Christmas tree. Enjoy the best experience by choosing a well-hydrated tree. One way to check is to gently grasp a branch and pull away, running it through your hand. If it's a good tree, it will hold onto its needles. If it has started to dry out, you'll end up with a lot of needles in your hand.
Some trees hang onto their needles better than others. Some of the prizewinners for needle retention are Douglas fir, Fraser fir, white fir, white pine, and red pine.
Keep your tree looking fantastic through the holidays by locating it in a cool place (the cooler the temperatures, the longer your tree will stay green) and keeping an eye on the water level in the stand.