- About Extension
- Get Involved
- Statewide Locations
To-Do List - December
by Karen Bodner, MG
Crops like Brussels sprouts, carrots, and parsnips are sweeter if harvested after a frost. If you're a winter gardener, don't stop now. Radishes, lettuce, and many greens will germinate in soil temps as low as forty degrees and can be sown directly outside, preferably under cloches that keep them cleaner and accelerate their growth. If you have space indoors, you might be better off sowing these items there under lights and then transplanting them later. Be sure to prepare beds now, however, and protect them with mulch or cloches.
I find that removing the lower, rotting leaves of lettuces goes a long way towards reducing pest problems, especially slugs, but then so does cloching the plants so water doesn't splash on them. Garlic and shallots can still be planted; however, remember there is a direct and important correlation between the amount of root development, subsequent leaf growth, and finished bulb size. Since the roots develop first, a more vigorous root system established before leaf growth will result in a larger bulb.
If you haven't gotten around to it yet, mulch your active vegetable beds two inches deep, especially asparagus, artichoke, and rhubarb. Rhubarb can be divided through December if need be. Start seeds for an indoor winter herb garden. When storing root crops in the garden, cover with six to twelve inches of loose mulch. Check a few specimens for insect damage before going to all that trouble, and be sure to periodically check produce stored indoors for decay.
Perennials, herbs, and bulbs
After removing weeds, mulch your perennial beds; shredded leaves are a favorite. Continue deadheading, and cut back dead or diseased plants and branches. Reduce fertilizer applications to houseplants.
Dahlias should be dug by now. It's still OK to plant Spring-blooming bulbs; just remember, the later you plant, the later they'll come up. Wet soil is really the only deterrent to planting these bulbs right through December.
After flowering, cut chrysanthemums and asters to about six inches above the ground. Cut cannas to ground and cover with a a thick mulch if not digging to store. Incidentally, I haven't lost a canna yet, mulched or unmulched.
Prepare potting mix for new houseplants. A mix of one-third soil, one-third sand, and one-third peat moss is standard.
Propagation: Direct sow hardy perennial and annual seeds, hardwood cuttings: Rosmarius, Salvia.
Layering: Peonia. Best done in November. Better wait now.
Root cuttings: Japanese anemones, bleeding heart, Echinops, Phlox paniculata and Oriental poppies.
Leaf cuttings: Begonias.
Trees and shrubs
Remove suckers from lilacs and other similarly flowering shrubs. Haven't gotten those trees and shrubs in yet? Go right ahead, but be sure to water in well and add a handful of bone meal to the planting hole. Rake and destroy fallen, diseased fruits and leaves to minimize disease and pests. Tie up or otherwise support any evergreen branches that are vulnerable to winter weather damage. Specifically, wrap columnar evergreens.
Hydrangeas can be pruned now; however, many gardeners leave the stalks over winter to protect the crown and new growth from harsh weather. Any remaining rose leaves should be removed and the area below the plant cleared of debris. This will go a long way toward disease prevention. Spread fresh mulch around your shrubs now, remembering to leave the trunk clear. Be sure to removed diseased leaves if necessary.
If you started cuttings of silver-leafed plants last September, protect them in a frost-free place.
Hardwood cuttings: Vitis and Weigela.
Semi-mature cuttings: Chamaecyparis.
Division: Rheum and Syringa
Layering: Too late for this year. Wait.
Root cuttings: Rhododendron and Camellias.
Fruits and Nuts
Harvest winter pears (European) before ripe and, after a few weeks of cold storage, bring indoors for ripening. Place mulch around berries and tie raspberry canes to wire; prune to one foot above the wire, or wrap canes around the top wire. Check cut canes for holes at the base of plant for evidence of crown borers. When cutting fruited canes down, cut close to the ground to reveal solid stem, and discard any stem pieces that are hollow; they may harbor larvae.
Lawns and Cover Crops
Apply lime and check for moss and other symptoms of problems such as rust. Keep an eye out for drainage problem spots in your general yard area during rains. When mowing for the last time this season, leave your grass longer rather than shorter.
Fava beans are a safe bet for cover crops planted this late. Others may grow a bit then linger and die a slow death. It would be better to mulch your unplanted veggie beds with four to six inches of shredded leaves, manure (work in if fresh), or compost.
Mulch, mulch, mulch everything! Adding organic matter and reconditioning the soil is one of the most important things you can do for your garden over the winter.
Be diligent about garden clean up and disposal; never compost diseased plant debris, but you could leave a few select seedheads for our non-migrating bird friends.
Walnut and laurel leaves may have allelopathic properties and should be composted separately or discarded. Just sprouted weed seeds will develop large root systems over the winter and explode in the spring; better removed now than later! Clean and store garden tools and equipment. Browse new seed catalogs as they come in; you can find spring in winter when you dream about next year's garden.
Our little soldiers are now entering their winter headquarters; however, I'm sure the battle continues to some extent. Although cultivation can effectively disrupt many soil-dwelling pest populations, it will also destroy beneficials using the same housing facilities.
I believe in having permanent beds surrounding and within a garden to provide undisturbed living quarters for the good guys. I have seen a remarkable reduction of pest problems since adding these islands, along with a small pond, to my combination veggie-flower-herb garden. These beds are of the following types: permanent informal/Chinese (without perimeter structures); double-dug; and intensively planted, mulched raised beds.
Birdbaths should be maintained in clean condition until freezing weather threatens, at which point they should be drained. Our feathered friends would love some suet and other goodies to supplement a decreasing food supply.
If you grow cole crops and brassicas, check plants for evidence of the imported cabbageworm larva which I usually find along the inside leaf stems.
Here is our overwintering bug roster. Beneficials are italicized.
|A =Adult||L =Larva||N =Nymph|
|E =Egg||P =Pupa|
western damsel bug-A
carrot rust fly-L
green peach aphid-E
western flower thrips-A
holly and soft scale-N
|minute pirate bug-A
alfalfa leafcutting bee-L
wstrn cherry fruit fly-P
western potato flea beetle-A
str'berry crown borer-L
str'berry crown moth-L
wstn r'berry frtwrm-A
peach twig borer-L
elm leaf beetle-A
white grub beetles-AL
walnut husk fly-P