December Garden Checklist
What to Plant: All Elevations
Sow seeds of leafy greens and root vegetables, such as Swiss chard, kale, collards, mustard greens, spinach, bok choy, leaf lettuce, arugula, radish, carrot, beet, turnip, parsnip and rutabaga. Try ‘Hakurei,’ a white radish with a sweet, fruity flavor that can be eaten tops and all. ‘Space’ is a spinach variety that is ready for harvest in 25 days. Prepare the garden bed for seeding by mixing 2 to 3 inches of fine compost into the soil and raking it smooth. Cover new plantings with floating row covers, available at most garden centers, to keep birds from eating emerging seedlings.
Mix wildflower seeds with a pound of sand to make them easier to spread uniformly. Use a sprinkler to help the seeds settle and make good contact with the soil. Perennial wildflowers, such as brittlebush (Encelia farinosa), globemallow (Sphaeralcea ambigua), desert senna (Senna covesii) and desert sunflower (Geraea canescens), will come back from the roots year after year. Cut them back once the season is over, in late spring. Annual native wildflowers, including California poppy (Eschscholzia californica), tidy tips Arizona lupine (Lupinus arizonicus), blue flax (Linum lewisii) and desert bluebells (Phacelia campanularia) will die after blooming in the spring but will reseed if left in place until the seed pods dry and split.
Transplant such culinary favorites as dill, cilantro, parsley, chives, oregano, thyme, marjoram, lavender and rosemary. Don’t forget your feline friends and put in some catnip for them, too. Herbs do well planted directly in the ground or in containers. Any potting mix is fine to use in container herb gardens; just be sure the pot drains so that the roots don’t become water-logged, which will kill the plant.
December is a great time to plant hardy trees, shrubs and groundcovers. Hardiness refers to the plant’s ability to withstand cold temperatures, so choose species that can survive the coldest winter temperatures in your location. Chaste tree (Vitex agnus-castus) is a purple-flowered deciduous plant that is hardy to 15 degrees. Cape honeysuckle (Tecoma capensis) is a fast-growing evergreen shrub that produces orange-red blooms and is hardy to 28 degrees. Tufted evening primrose (Oenothera caespitosa) is a clumping groundcover that spreads to about 2 square feet and survives temperatures as low as
What to Plant: Middle Elevations
Plant onion from seeds or sets, which are small, dry bulbs. Onion sets will usually mature in 100 days, whereas seeds can take a few weeks longer. Look for day-neutral types that are not sensitive to day length.
You can transplant evergreen trees and shrubs during the cold winter months. Atlas cedar (Cedrus atlantica) has blue-green foliage and can reach 60 feet tall by 40 feet wide. Place it in a location where it can reach its full size and won’t interfere with structures or utility lines. Blue Rug juniper is an evergreen groundcover that doesn’t exceed 1 foot in height and spreads 6 to 8 feet wide.
What to Plant: High Elevations
Even though winter temperatures are too chilly for most outdoor gardening, you can still grow fresh, green veggies indoors near a bright window or under a grow light. Sow seeds of broccoli, cabbage, cauliflower, sunflower, radish or mustard in shallow 2-inch-deep planting trays. Make sure the tray has drainage holes, otherwise the seedlings can drown and die. Fill the tray with planting mix, then spread the seeds over the surface. Cover with more planting mix, about 0.25 inch is enough to keep the seeds moist but not too deep to inhibit rapid germination. Harvest microgreens once they produce their first true leaf by cutting the tiny plants off right at the soil line with clean, sharp scissors. Use fresh soil for every new planting to avoid damping off, or seedling wilting and death due to fungal infection.
Garden Maintenance: Low Elevations
ORDER BARE-ROOT PLANTS
Order bare-root roses, fruit trees, raspberries and grapes for delivery and planting in January or February. Look for cultivars that require fewer than 400 chilling hours, otherwise winter temperatures may not be cold enough to support fruit development.
Plant water requirements are lowest during the winter. Mature trees may only need to be watered monthly, and shrubs can generally survive on water administered every two weeks or so. Recent transplants may need to be watered every few days until the roots become established.
Middle and High Elevations
Keep your gardening tools in optimal condition by thoroughly cleaning them every year. First, remove any caked-on soil with a strong stream of water and scrub them with steel wool. Next, soak the tool in a bucket filled with soapy water for a few minutes, then rinse and thoroughly dry before storing. Keep your tools dry to avoid rust.