December in the Contra Costa Garden
December Garden To Dos
General Garden Care
- Turn off irrigation systems if raining—if not raining, reduce time and frequency to the minimum amount of time needed to keep plants alive.
- Remove summer-created watering basins to prevent standing water around trees and shrubs from causing root or crown rot.
- Protect tender plants if frosts are predicted: use outdoor lights or build a light weight frame and cover. Antitranspirants such as ‘Cloudcover’ will provide a bit of protection. http://www.ipm.ucdavis.edu/PMG/GARDEN/ENVIRON/frostdamage.html
- Avoid compacting wet soil: minimize walking or driving and don’t work wet soil.
- Avoid walking on frosted grass; the cells rupture and turn brown.
- Clean up all garden beds; compost spent garden plants.
- Turn compost; cover if raining.
- Use rainy days to clean, sharpen and lubricate garden tools; —store in dry area.
- Check plants under eaves—are they getting enough water?
- Order seeds (this month or next).
- Inventory all pesticides and take unneeded and outdated chemicals to the household hazardous waste center; consider using IPM methods rather than replacing chemicals. http://www.ipm.ucdavis.edu/index.html.
Fruits & Vegetables
- Pile dead leaves into a trench in unused vegetable beds, and cover with soil. By next spring, the leaves will be composted and the beds ready for planting.
- Control peach twig borer, San Jose scale, mites or aphids on apricots with a dormant oil spray. Dormant oil sprays can be applied to dormant ornamentals as well as fruit trees. http://www.ipm.ucdavis.edu/TOOLS/PNAI/pnaishow.php?id=39
- Remove “mummies” and fallen fruit to minimize spreading diseases next spring.
- Prune Feijoa sellowiana shrubs after fruit is harvested.
Flowers & Landscaping
- Prune winter-flowering shrubs just after bloom.
- Prune hardy deciduous and evergreen trees.
- Prune evergreens for holiday decorations.
- Water living Christmas trees.
- Plant ornamental trees and shrubs EXCEPT Subtropicals.
- Plant frost-tolerant perennials such as Ajuga, English ivy (Hedera), heuchera, hosta, lamium, lysimachia, ornamental sages, and Tiarella; frost-tolerant annuals such as calendulas, cinerarias, cyclamen, pansies, English primroses, fairy primroses, Primula obconica, and snapdragons.
- Select blooming azaleas and Camellia sasanqua varieties, foliage plants: dusty miller, ferns, liriope, or dwarf Nandina domestica.
- Pre-chill tulips and hyacinths for forcing indoors.
- Mulch bulb beds to protect from freezing and to conserve moisture if winter is dry.
- Check all hardy bulbs potted earlier; move indoors into good light when roots develop and 2 to 3 inches of new growth is visible.
USDA zones range from 8-9B
Sunset zones range from 7-17
Average max. temp. 54.7°F, 12.6° C
Average min. temp. 39.3°F, 4.1°C
Average rainfall 4.38”, 11.13 cm.
The winter solstice falls on December 21.