Helpful Garden Tips for December 2020
If you garden, you’ve probably noticed our garden centers have been busier than usual this year. And many more people have started vegetable and herb gardens or finally completed that landscaping project they’ve been planning for years. December is the transition from fall, in which we can complete a lot of garden projects, and in which it’s best to let the garden rest. I hope you can take some time this month to use the garden to the fullest, by harvesting edibles and using your ornamentals for natural decorations and gifts. The December garden can be full of beautiful shapes, colors, and scents. And it can be pretty busy, with late season foraging by birds, bees, butterflies, moths, and mammals.
PLANTING: Wrap up planting trees, shrubs, perennials, and ground covers by mid-month. Plants that are frost sensitive shouldn’t be planted until spring. Even for frost-hardy species, use a good three- to- four- inch layer of mulch to protect plant crowns and roots from freezing. Bare-root planting begins in December. Finish planting bulbs for spring color.
In the edible garden, in addition to perennial herbs, you can still transplant seedlings of most cool-season vegetables, if you can still find them in garden centers. Also plant bulb onions, asparagus, and rhubarb. These last two are perennials, so you won’t be harvesting them until well into next year. You can also plant lettuce and related salad green seeds in cold frames. I love my home-built cold-frames, which are made from plywood, reinforced corners, and covered with old windows (winter), window screens (spring and fall) and shade cloth (summer). I place the wooden boxes on weed cloth, a layer of cardboard, and then fill them half with composted manure and straw from my livestock barns, and then fill them up the rest of the way with good quality potting soil. The cold frames I build are about 1 foot high and range from two feet wide and three feet long I can move around between seasons and larger boxes that stay in place. I’ve grown some of my best vegetables in these frames, away from the predation by insects and birds and with great temperature control. It’s kind of like combining raised bed gardening with greenhouse growing.
MAINTAINING: Watch for frost warnings and protect your sensitive plants. Plants will survive better if kept moist but not overwatered. Remove old dried-up fruits, called “mummies” that are left hanging on fruit trees. Water citrus trees well this month if the rains aren’t steady in order to have a good crop next year. Also, deep water your other trees during a dry spell that lasts more than two weeks, even if they’re dormant.
You can begin to prune your winter deciduous trees and shrubs, or wait until January, especially if plants aren’t fully dormant and safety isn’t an issue. Prune your grape and other vines this month. Force your roses into dormancy by removing leaves that haven’t fallen. Don’t prune if frost is expected within the week. Mow cool weather lawns, which should be actively growing now, at three inches. This also applies to over-seeded lawns.
If you had major problems with aphids, mites, scale or whitefly on your fruit trees or roses, spray with dormant oil spray to kill overwintering adults after the leaves have fallen. Handpick slugs and snails or set out iron phosphate as a bait. You must replace iron phosphate after a rain, but it’s not toxic to people, pets, and beneficial insects and won’t harm soil microorganisms either. In late December, spray early blooming peach and nectarine trees with copper fungicide to control peach leaf curl.
See any white moths around your winter veggies? The moth is looking for good spots to lay her eggs, which will hatch into the cabbage lopper and eat holes in the leaves, sometimes decimating the crop. You can’t do much about the moth, but seeing the moth is a signal to start looking under the leaves for the next several days to snag the small, green caterpillars before they do much damage. Large plants can survive some damage, but seedlings can be devoured. Chemical control is BT (Bacillus Thuringieis, also sometimes labelled as Caterpillar Killer). Be sure to spray plant leaves thoroughly on the tops and bottoms. Remember many caterpillars, especially on ornamental plants, do little harm and turn into desirable moths and butterflies. And all Lepidoptera are food for birds, lizards, toads, and other creatures in the food chain. So use common sense and a little tolerance for damage to encourage a healthy garden full of interesting life, even in the urban neighborhood.
Finally, keep up with cool season weeds so it doesn’t become a tiresome and overwhelming job later. Common household white vinegar or commercially formulated non-systemic organic herbicide can be kept in a labeled spray bottle in the garden to zap weeds on sunny days. Or lightly hoe them out. You can also try piling on more mulch and shading them out, which works well in these weak-sun days.
CONSERVING: Leave a pile of branches from trees and shrubs for birds to shelter in. Keep the bird feeders filled. And don’t forget the water. Small creeks as part of a water garden design, mister- style sprinklers, or a bird bath with fresh water are all popular with our wild bird friends. When getting ready to prune trees, examine the high branches of large trees for bird nests and avoid pruning if hawks or other birds are nesting.
If you haven’t already done so, cut the flowers off tropical and other non-native, orange-flowered milkweed varieties. The Monarchs that stick around because of a ready food source won’t survive the cold winter; they need to migrate south. You may want to consider replacing it with a native milkweed next year. On the other hand, we have so many hummingbirds that don’t migrate, it’s OK to continue to provide them with hummingbird feeder food through the winter.
GOOD NEWS! Master Gardeners will be available to answer your home gardening questions at a few limited sites in the near future! Come visit us at:
Lindcove Citrus Tasting, December 11 and 12, 8 a.m.-noon, at Lindcove Research and Extension Center, 22963 Carson Avenue, Exeter, (559) 592-2408
Contact the Master Gardeners in Tulare County: (559) 684-3325; Kings County at (559) 852-2736