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December Checklist



Cool-season vegetables—Sow seeds of peas, radish, carrot, turnip, beet, green onion, rutabaga, bok choy, spinach, leaf lettuce, kale, chard, arugula, mustard and collard greens. Give peas a vertical trellis to save space and make the pods easier to harvest. Plant asparagus crowns in a sunny location where they can remain undisturbed for several years and cover with mulch. Transplant starts of broccoli, cabbage, cauliflower, kohlrabi, head lettuce and celery. Give plants plenty of room to grow. Broccoli and cauliflower can spread to 2 feet wide.

Buy tomato seeds—If you are planning to grow tomatoes from seed this spring, start shopping for seeds now to start indoors next month. Look for ‘Tye-Dye,’ a yellow-and-red slicing tomato that is low-acid and sweet. For a snacking type, try ‘Texas Wild Cherry,’ a prolific, early-maturing variety.

Annual flowers—Create festive beds and container gardens with potted colorful poinsettias, geraniums, petunias and cyclamen. Plant seeds of Sonoran Desert native wildflowers, such as lupine (Lupinus sparsiflorus), poppy (Eschscholzia californica), owl’s clover (Orthocarpus purpurascens) and bluebells (Phacelia arizonica). Prepare the soil by mixing compost into the upper 2 to 3 inches and raking it smooth.

Herbs—Sow seeds of cilantro, dill, chives, parsley and chamomile. Plant transplants for perennial oregano, thyme, rosemary, bay, mint and catnip. Mint has a tendency to spread and overtake the garden, so consider planting it in a large nursery container with the bottom cut out. This will allow for drainage but confine the roots to the allotted space.

Shrubs, trees and vines—Select nursery plants that are free of pests and damage. Check to be sure there are no circling roots and that the stems have not been buried beneath the soil line in the pot. Plant perennial landscape plants where they have ample space and won’t block windows or interfere with driveways, fences or other structures. Immediately remove the nursery stake and only install support stakes if the tree cannot stand on its own.


Planting outdoors must wait until temperatures rise in a few months, but you can grow many traditional holiday plants indoors.

Poinsettias—A rainbow of colors are available these days, in addition to the traditional red. Look for yellow, orange, white and marbled types. Be advised that all parts of the poinsettia plant are toxic to animals, so keep them out of reach of children and pets. The white sap can cause irritation, so wash it off immediately if it
contacts the skin.

Live Christmas trees—Select a living tree that can be transplanted into your landscape after the holiday is over. Ask your local nursery for evergreen pines, firs, spruce and cedar that are adapted to your elevation.



Care for cut Christmas trees—Make a fresh cut in the trunk just before plunging it into water. Fresh trees will transpire lots of water, so check the reservoir in the stand once or twice each day and refill as necessary before it is dry.


Protect against frost—Cover sensitive plants with frost cloth, ensuring that the fabric reaches all the way to the ground. Repurpose  plastic foam cups to protect the tips of cacti and euphorbias on cold nights. When frost is predicted, deeply water the soil around plants. At night, the moist soil radiates heat.

Exclude pests from vegetable gardens—Cover newly planted vegetables with floating row covers, available at most garden supply stores. This lightweight fabric keeps flying insects and birds at bay while letting sunlight through and offering protection against killing frost.

Thin and harvest vegetables—Check seed packets for recommended spacing and thin seedlings accordingly to give them room to grow. Rinse the culled seedlings in cold water and use them in salads. Root and leaf vegetables don’t need to “ripen” like fruit and seed crops, so pick them while they are small and sweet. Harvest outer leaves of greens such as kale and chard; new leaves will grow from the center all season long.


Knock accumulated snow from tree limbs to prevent them from snapping under the weight. If a limb does break, remove it entirely using proper pruning technique. Do not leave a stub, and do not cut flush against the trunk. Avoid stripping the bark when making the cut, as this will impair the tree’s ability to recover in the spring. Visit the National Arbor Day Foundation’s website for an illustration of how to make a good pruning cut:

Water landscape plants—Winter’s cold, windy weather stresses perennial vines, shrubs, grasses and trees. Use irrigation to supplement natural precipitation once this month, making sure that the water penetrates to a depth of 1 foot for grasses, 2 feet for vines and shrubs, and 3 feet for trees. Apply the water around the drip line of the plant, the area in the surrounding ground that corresponds to the outermost tip of the branches or canopy, where rainfall is naturally channeled and there is a concentration of absorbing roots.

Apply mulch—If you haven’t already done so, apply a thick (6- to 12-inch) layer of mulch, such as pine needles, around plants. Mulch serves to insulate the soil against drastic temperature changes and slows the evaporation of precious
soil moisture.


Kelly Young is an agroecology researcher and educator with a master’s degree in botany from ASU.


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