December is usually pretty mild in Zone 8. It is a great time to plant trees, shrubs and vines. It’s also time to “lay by” the crops already harvested from the summer garden. Store sweet potatoes, Irish potatoes and other root crops in a root cellar or in boxes of sand out of the light. Use fresh herbs to make herbal vinegars and butters. Freeze pesto and give containers of it for Christmas to non-gardening friends. Bouquets of fresh herbs also make lovely hostess gifts.
Sweet peas may still be planted in good weather. Continue to plant roses. Bulbs can be planted all month.
Indoors, keep cyclamen and paperwhite narcissus you have forced in a cool spot to prolong the blooms. As soon as a flower fades, remove it. Water paperwhites sparingly if in soil; if growing in water, be sure to keep the water level above all the roots. Amaryllis are also wonderful and colorful flowers that can be forced for holiday blooming. And they make great gifts.
Onions can survive all winter, so leave them in the ground. Turnips, cabbages, collards and other kohl plants can survive down to 10 degrees. Harvest broccoli as heads develop. Remember that in Zone 8’s climate — short periods of cool weather — broccoli heads won’t get huge like the ones in the grocery store. Harvest at 4 to 6 inches. Harvest greens on a cut and come again basis. They will continue to grow on any day that’s above freezing.
You will be harvesting many vegetables this month if you planned your winter garden well. Arugula, beets, bok choy, cabbage, carrots, greens, lettuce, spinach, winter squash and turnips will all be available this month.
Harvest tender crops such as basil, tomatoes, sweet potatoes and others before a hard freeze. Pull out old stems and roots and plant a cover crop such as clover, vetch or peas in unused areas of the garden. In spring, till in the cover crop for green manure.
SHRUBS AND TREES
Most woody plants can still be planted until February. Mulch any plantings well and water in, just as you would any other time of year. Guy-wire until spring any tree more than three inches in diameter.
A paste of wood ash and water spread on tree trunks repels borers if they are a problem in your area.
Prune evergreens and bring the boughs indoors for fragrant decorations. Use Nandina and holly berries for red accents.
Plant woody vines like Carolina jessamine, American wisteria and cross vine now near sturdy supports. Tie the vines up with twine or plant ties. Always check that any vine you plant is not invasive before you use it. English ivy and trumpet vine, as well as Chinese wisteria can really damage a landscape if they get loose.
You can propagate cuttings of woody plants in late fall and winter by dipping cuttings in rooting hormone and putting them in boxes full of sand. Leave them outdoors in a protected place covered with white plastic or floating row cover. Make sure the sand stays moist. It may take several months before the cuttings grow enough to transplant.
Rake leaves into piles, run over them with a lawn mower to shred, rake them back into beds or around trees as mulch. Add mulched leaves to compost pile. Turn compost before it freezes.
Bermuda sod may still be planted, but be sure to keep it watered throughout the winter.
Drain the gas from your lawnmower or run it until it’s out of gas. Don’t leave it out in the rain or water will get in the gas tank.
Look at Home Depot’s website for seeds and seed sprouting supplies. Plan the spring garden. Draw plans for garden hardscape and work toward building structures such as raised beds, walkways, walls or decks during the cool months.