December

Time for rest, chill December
​Sever ties with old
Making room for new

With all the hustle and bustle of the holiday season, it is easy to put aside garden tasks for another time. We need to rest when we can, too, just as our garden plants do each winter. But December is an excellent time to prevent future problems in the landscape. With just a little bit of effort now, we can have bigger harvests and healthier plants next summer.

Poinsettias

Bare root planting

December is an excellent time to install bare root plants in California and other warmer regions. Any of these bare root plants can be planted in December:

• artichokes
• asparagus
• berries
• fruit trees
• grapes
• horseradish
• iris
• kiwifruit
• nut trees
• rhubarb
• roses
• strawberries

Bare root pear tree

Blackberries

If you are growing blackberries, December is a good time to remove any canes that produced fruit this year. Leave up to 9 canes from each plant, which can be trellised in spring, once they start growing. To get more lateral, fruit-bearing canes, cut off the tips of canes.

Cool weather crops

Plant cole crops and salad greens now. Broccoli, cabbage, cauliflower, collards, and kale thrive in our California winters, along with lettuces, mustards, endive, Swiss chard, and spinach. You can harvest these crops continuously through the winter months with just a little bit of protection. Leeks and onions can be planted in December.

Cool weather Swiss chard shares a raised bed with spring-growing asparagus

​Be sure to monitor plants closely for signs of cabbageworm, slug and snail feeding. It is easy to handpick these pests. (My chickens love them!)

​Compost piles

Occasional rains will help keep compost piles moist, but remember to turn your compost pile to incorporate the oxygen needed by helpful microorganisms. You may need to cover your compost pile during heavy rains to prevent losing all those valuable nutrients.

Divide and cut perennials

Some plants will perform better next year by being cut back or divided in December. Dividing plants means digging them up and separating clusters of roots or bulbs, and replanting them with room to expand. Artichokes, bunch grasses, chrysanthemums, rhubarb, and many spring-blooming bulbs benefit from this treatment.

Dividing Shasta daisies

Firewood

It might not feel like the holiday season without a crackling fire, but be careful about where you get your firewood. Several pests and diseases can make their way to your trees by hitching a ride on firewood. Invasive shot hole borers, polyphagous shot hole borers. and goldspotted oak borers are just a few tree pests that can carry fatal tree diseases, such as Fusarium dieback.

Frost protection

You can protect your crops by using the USDA Hardiness Map to determine your planting zone and learning when to expect frost to occur. I’m in Zone 9b, which means my first and last frost dates are November 15 and March 15. But those dates are not written in stone. This year, frost appeared on my lawn two weeks earlier than predicted.

For plants that may be damaged by frost, you can protect them by draping sheets, tarps, or other light fabric over and around them using poles and string. Do not allow the fabric to touch the plants. Umbrellas and old fashioned (not LED) Christmas lights can also provide some protection. Potted plants can be brought indoors or closer to protective structures. And be sure to water frost sensitive plants. Damp soil holds more heat than dry soil. Also, mulch can stabilize below ground temperatures. If frost damage does occur, resist the urge to clip away the damaged bits - they create a barrier against further frost damage. If it looks really hideous, leave it covered.

​Garden bed care

As many annuals end their lifecycle, be sure to remove them from the garden bed by cutting them off at soil level. This allows valuable soil microorganisms the time they need to migrate to another plant and the roots will add nutrients to the soil as they decompose. Adding aboveground plant debris to the compost pile not only creates nutrient-rich compost, but it interrupts the lifecycle of many garden pests and diseases. If plant materials are already diseased, they should be thrown in the trash.

Holiday plant care

Poinsettias, Christmas trees, Christmas cactus, amaryllis, and many other holiday plants find their way into our homes in December. Most of these plants prefer cooler temperatures and higher humidity than our homes can provide. Keeping plants away from heater vents and misting them occasionally will help. Also, avoid overwatering.

Sprinklers

Winter irrigation is largely dependent on the weather. December is a good time to turn off the sprinklers and monitor the soil with a moisture meter. Cooler temperatures mean slower growth but some water is still needed. Also, if an area becomes saturated with water, avoid walking on it. This prevents soil compaction.

Tree care

If a tree branch is torn by heavy winds, you can help it heal by cutting the wound to make it a flat surface, close to the trunk, but not cutting into the branch collar. You do not need to paint the wound. Instead, allow the tree to protect itself. It will grow a callus over the area. You may, later on, need to provide the callus with sunburn protection. These other tips will also help your trees stay healthy this winter:

• Put those fallen leaves to work for you. Add them to the compost pile or leave them where they fall (assuming they are healthy). Diseased leaves should be kicked to the curb.
• Apply dormant oil to fruit and nut trees after all the leaves have fallen to interrupt pest life cycles.
• Whitewash exposed wood with 1 part white latex paint and 1 part water for sunburn protection.
• Prune out dead, damaged, diseased, and crossed branches, remove unproductive wood, and implement your tree training plan. Cherry and apricot are exceptions - they should only be pruned in dry, summer weather, to prevent Eutypa dieback.
• As trees enter the delayed dormant period, treat for shothole fungus and other diseases with dormant oil sprays. 
• If peach leaf curl was a problem this past year, treat trees with fixed copper after the trees have entered dormancy.

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With just a little care now, you can be sure your garden will get through winter for a better spring to come.

Happy holidays, fellow gardeners!