December Garden Checklist
Learn what to plant this month, get maintenance advice, and troubleshoot your gardening challenges with an expert.
By Kelly Young
What to Plant
Cool-Season Vegetables–Transplant broccoli, cauliflower, Brussels sprouts, cabbage, radicchio and head lettuce. Space plants 6 inches apart to allow enough room, at least 1 square foot per plant, to reach mature size. Sow seeds of beets, carrots, radishes, leeks, turnips, parsnips, rutabagas, leaf lettuce, kale, spinach, Swiss chard, and snap and sugar peas. Trellis peas to save space.
Tomatoes–Start tomato seeds indoors for transplanting outside in February. Use freshly purchased potting soil and pots that have been sterilized to reduce the chances of losing young seedlings to disease. You can sterilize previously-used pots by spraying them down with a solution made by diluting one part bleach with nine parts water. Plant seeds no deeper than 0.25 inch and keep the soil damp but not soaking wet. Place pots in a sunny window or use grow lights to encourage rapid development.
Hummingbird Attractants–Make your garden a bountiful buffet of nectar for our tiniest feathered friends. Hummingbirds love desert-adapted autumn sage (Salvia greggii), Parry’s penstemon (Penstemon parryi), yellow bells (Tecoma stans), ocotillo (Fouquieria splendens) and Mexican honeysuckle (Justicia spicigera), all of which require minimal irrigation and care.
Cool-Season Annuals–Fill beds and containers with an assortment of colorful annuals. For a dazzling display, plant a rainbow of cold-loving selections, such as red geraniums, pink begonias, orange calendulas, yellow gazanias, green bells of Ireland, blue petunia and purple lobelia.
Herbs–Sow seeds of cilantro, dill, parsley, fennel and chives. Transplant oregano, thyme, marjoram and rosemary, an attractive, woody, low-growing shrub with culinary applications. The plant’s trailing tendrils look lovely cascading over a low wall, and its pale purple blossoms are a favorite of honeybees.
Middle and High Elevations
Living Christmas Trees–Conifers, such as Douglas fir (Pseudotsuga menziesii), Southwestern white pine (Pinus strobiformis) and Colorado blue spruce (Pinus strobiformis), can survive indoors for a week or two before being transplanted outside into their forever home. Choose a location in your landscape with ample room for the tree to grow. To avoid interference with buildings and fences, plant trees and shrubs no closer than half of their width at maturity. For example, a tree that will grow a canopy eventually reaching 20 feet in diameter should be planted at least
10 feet from structures. Avoid future pruning headaches and steer clear of overhead utility lines.
Houseplants–Succulents, such as jade plant (Crassula ovata), Christmas cactus (Schlumbergera spp.) and cylindrical snake plant (Sanseveria cylindrica), require minimal maintenance and thrive in the low-light and low-humidity conditions in homes.
Decrease Irrigation–Cool temperatures and gentle winter rains reduce the amount of supplemental water that plants need for the next few months. To optimize every drop applied, extend the length of time between irrigations rather than reducing the amount of water provided. Established desert-adapted trees and shrubs may only need to be watered once a month during winter. Water should be applied near the dripline or edge of the plant canopy, where the majority of absorbing roots are concentrated. Use a soil probe to ensure that the water is reaching a depth of 1 foot for turf, annual beds and vegetable gardens; 2 feet for shrubs and vines, and 3 feet for trees.
Protect Plants from Cold–Nighttime temperatures may dip below freezing for the next few months, so have frost cloth handy. Appropriate frost cloth is lightweight, allows for gas exchange and is large enough to reach all the way to the ground when covering plants. Resist the urge to prune frost-damaged plants. Pruning stimulates new growth, which then may be damaged by subsequent frosts.
Thin Cool-Season Vegetables–Selectively cull vegetable seedlings so they are spaced according to the recommendations on the seed packet. Overcrowding can lead to poor root development and restrict air circulation, which may create a favorable environment for fungal disease.
Feed the Soil–Enrich garden soil with organic matter such as compost, which, in turn, feeds beneficial microbes. Leave leaf litter, especially pine needles, on the ground’s surface and allow it to gradually decompose and release nutrients.
Manage Snow–Knock accumulated snow from tree limbs to prevent breakage. Stack snow around the driplines of plants; as it melts, the water will be available to roots.
My husband and I just bought our first home with a small yard and would like to plant vegetables. What’s the minimum recommended size for a garden?
Your garden can be as small as a single radish growing in a repurposed fast-food cup, if that’s all you have room for. As long as there is access to soil, water and six to eight hours of sunlight each day, you can grow a vegetable garden. Beginning gardeners should start small and expand as they build confidence from their success. Consider starting with a 3-foot-square space the first year. You might be surprised with how much produce can be grown in that area. Each square foot can produce 12 radishes or carrots; nine beets, onions or turnips; or four bunches of leaf lettuce, spinach, chard or kale. Plus, it’s easier to keep small gardens free of weeds and other pests.
How can I tell if my plants are frost-sensitive before it’s too late? I am new to the Valley, and I don’t want everything to freeze to death in the first year.
The first thing to do is identify the plants in your landscape. This can be accomplished with the help of garden-savvy friends and neighbors, by sending photos to your local Master Gardener (www.extension.arizona.edu) or by hiring a landscaper who has knowledge of each species’ cold-tolerance, or “hardiness.” You can do some online research to find out for yourself. It is unlikely the entire landscape is composed of tender, tropical types. Young plants installed in the last year or two tend to be
more sensitive to frost than their mature counterparts. Large, mature plants have probably survived winters without much damage. Do a close inspection after the first cold night. Check for leaves that are wilted, brown, black or crispy, which are indications of cold damage. Do your best to ignore the damage until no more freezing temperatures are expected, usually sometime after Feb. 20. Pruning stimulates growth, and the flush of tender new leaves brought on by pruning is also likely to freeze.
As we head into the holiday season, I’d like to be more eco-conscious. What kind of wrapping paper can be composted?
Thank you for considering the environment in your holiday planning. As you suspect, not all gift wrap is good for the compost heap. Plastic and glitter don’t decompose (in our lifetime, anyway), so stay away from colorful papers that may contain them. Try newspaper or paper shopping bags instead. Or pick up a roll of unwaxed butcher paper and decorate using nontoxic markers. After the gifts have been opened, shred the paper, which is a “brown” ingredient of compost, before mixing with “green” ingredients, such as kitchen scraps or lawn clippings.