What to do in your garden in December
Living Christmas tree. Norfolk Island pine ( Araucaria heterophylla), an evergreen Australian tree that's normally used as a houseplant, makes a great small Christmas tree. Hide the nursery container in an attractive cachepot and decorate the boughs with white lights, lightweight ornaments, and garlands. To keep your tree healthy for years to come, place it in a cool, bright room and mist with water often (daily, if practical). Water when soil is barely moist, and turn plant regularly so light reaches all sides. Monitor for scale, mealybugs, or spider mites and spray with an insecticidal soap if necessary.
Poinsettias safety. Some cats have a tendency to nibble on poinsettias and can become nauseated if they eat enough of the leaves. Display where cats can't reach them or decorate with other holiday plants such as azaleas, bromeliads ( Guzmania hybrids), Christmas cactus, freesia, gardenia, miniature roses, orchids, rex begonia, and star jasmine. Visit www.xmission.com/~emailbox/plants.htm
Containers. Pot up evergreen shrubs and trees in frost-proof foam containers and place them outdoors in a sheltered area, such as on a porch. Add creeping mahonia, English ivy, or hardy herbs, if desired, and decorate with bows, lights, or other outdoor ornaments. Water whenever the soil dries out. When temperatures threaten to dip below zero, bring the container into the garage or wrap it in a frost blanket. Plants that can be left in containers for several years before they get too large include boxwood, dwarf Alberta spruce, dwarf Colorado spruce, topiaried junipers, meserveae holly (Ilex x meserveae), and small pines, such as 'Vanderwolf's Pyramid' limber pine (Pinus flexilis).
Rosemary tree. These seasonal plants are widely available at garden centers and florists. To spruce them up for the holidays, set the topiary tree in an attractive container. Add ribbon or a small garland, winding it in a spiral from the top of the tree to the bottom, tucking it between the branch tips as you go. Decorate with small balls, dried flowers, pinecones, or seedpods. Set the plant in a bright room and water when the soil is barely dry to the touch. Rosemary can go outside after all risk of frost is past.
Assess winter structure. Make notes on where evergreens and ornamental grasses would add pizzazz to your winter landscape. For xeriscapes use nontraditional evergreens, such as hardy agaves, cylindrical opuntias, and yuccas. Mark the spot with a stake and add the plants as they become available in the spring.
Hyacinths. These bulbs normally need 12 weeks of chilling before they bloom indoors, but prechilled bulbs (available until early December at garden centers) bloom within a few weeks. Here's an ideal holiday gift: Plant an hourglass-shaped bulb vase with a single hyacinth, fill the bottom of the vase with shiny pebbles or marbles (from craft stores), then add enough water so it just reaches the bottom of the bulb. Tie a ribbon around the middle of the vase.
Cover shrubs. To prevent winter burn on marginally hardy woody plants, cover them before temperatures drop below zero. Evergreen boughs or pine needles are ideal, but frost blankets (held in place with landscape pins) also work as a temporary, though less attractive, measure. Plants to cover include autumn sage ( Salvia greggii), Eumorphia prostrata, hardy rosemary ( Rosmarinus officinalis 'Arp'), lavender, lavender cotton ( Santolina chamaecyparissus), Penstemon fruticosus, P. rupicola, stonecress ( Aethionema), thymes, and winter savory ( Satureja montana).
Prune evergreens. Now that needled and broadleaf evergreens are partially dormant, it's a good time to remove limbs, trim out twiggy growth, and cut back branches that are too long. Make cuts just beyond side branches (don't leave stubs) and prune evenly for shape. Save the trimmings for mulch or use them during the holidays. For decorations, soak the greens in a bucket of water and keep in a cool place until it's time to decorate. Spray finished arrangements with an antidesiccant to keep greens fresh longer.
Spread mulch. Winter mulch keeps the ground solidly frozen and prevents freezing and thawing cycles that can kill plant roots. Apply a 3- to 4-inch layer of lightweight mulch such as hay, leaves, straw, or pine needles over the entire garden. Cover the crowns of perennials, but keep mulch at least 12 inches away from the base of tree trunks to discourage nesting rodents. Remove winter mulch in spring to hasten soil warming.
Wildlife. Pile brush in an out-of-the-way corner of the garden to provide winter cover for birds, reptiles, and small mammals. Use care when digging in loose dirt so you don't unearth hibernating toads. Set out several types of bird feeders: suet cakes for chickadees, jays, and woodpeckers; thistle seed for finches and juncos; and sunflower seeds for cardinals and chickadees. Also provide a water source such as a heated pond for drinking and bathing, or place a thermostat-controlled de-icer in a birdbath or basin. Keep feeders and water sources clean to prevent the spread of diseases.
Care for Christmas cactus. This easy houseplant will flower several times a year with proper care. Set the blooming plant in bright, indirect light, water just enough to keep the soil evenly moist, and fertilize it every 7 to 10 days. When bloom ceases, rest the plant for six to eight weeks by placing it in a cool, dim room with no additional artificial light at night; water it sparingly. Afterward, move it back to a bright location, water more frequently, and within a few weeks it will bloom again.
Prevent dehydration. Arborvitae, azalea, boxwood, dwarf conifers, false cypress, and holly are susceptible to dehydration and windburn in winter. To protect them, spray the foliage with an antitranspirant, such as Wilt-Pruf Plant Protector (800/972-0726). One application lasts for several months.