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- Inventory all pesticides and take unneeded and outdated chemicals to the household hazardous waste center; consider using IPM methods rather than replacing chemicals.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.
Local Weather Information
Linked data is from the California Irrigation Management Information System (CIMIS) weather stations. Visit CIMIS web site.
Contra Costa County Stations
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.