More than in neigbhoring communities, Woodland Hills experiences extreme temperature ranges through the seasons. Summertime temperatures are very hot, while overnight temperatures in winter are often the coldest in the area.
The Woodland Hills climate is Mediterranean; using the Köppen-Geiger climate system, Woodland Hills lies in climate group Csa (Woodland Hills, Los Angeles, n.d.):
C - temperate climate with an average monthly temperature above 50°F (10 °C) in the warmest months
s = dry summers with the driest summer month less than 40 mm average precipitation
a = the warmest month's average temperature is above 72°F (22°C) with at least four months averaging above 50°F (10°C)
Woodland Hills experiences:
— Mild, rainy winters. Precipitation in Woodland Hills is similar to other areas in the west San Fernando Valley. In November 1950, the lowest temperature recorded in Woodland Hills between 1946 and 2006 was 19°F (-7°C) (Weather Warehouse, n.d.)
— Hot and dry summers. On July 22, 2006, Woodland Hills experienced the highest temperature ever recorded in Los Angeles County, hitting 119°F (48°C) at LA Pierce College (Woodland Hills, Los Angeles, n.d.).
CLIMATE AND PLANTS
Western Gardens plant zones
How well plants will grow in Woodland Hills depends in part on temperature, wind, and elevation. These maps describe the plant zones in Woodland Hills.
Zone 18 is classified as an interior climate, with the major influence being the continental air mass. Despite its proximity to Woodland Hills, the influence of the Pacific Ocean is less than 15% on the local climate.
In years past, citrus, apple, and walnut orchards flourished throughout Woodland Hills' Zone 18, but those orchards have since been replaced with homes and industry. "Although the climate supplies enough winter chill for some plants that need it, it is not too cold (with a little protection) for many of the hardier subtropicals like amaryllis. It is too hot, too cold, and too dry for fuchsias but cold enough for tree peonies and many apple varieties, and mild enough for a number of avocado varieties” (Time Inc. Lifestyle Group, n.d.).
Zone 19 is also classified as an interior climate, and receives little influence from the Pacific Ocean.
"Both zones, then, have very poor climates for such plants as fuchsias, rhododendrons, and tuberous begonias. Many sections of Zone 19 have always been prime citrus-growing country—especially for those kinds that need extra summer heat in order to grow sweet fruit. Likewise, macadamia nuts and most avocados can be grown here” (Time Inc. Lifestyle Group, n.d.). Succulents such as Aloe Blue Elf and Agave americana grow well in Woodland Hills, as do drought-tolerant ground covers such as Red Apple (but watch out for the wasps they attract) and Red Yarrow. Many varieties of roses grow well in both zones in Woodland Hills.
USDA hardiness zones
The following U.S. Department of Agriculture (USDA) Hardiness zone map indicates where plants may survive the winter.
The USDA plant hardiness map provides zones based on the average annual extreme minimum temperature over a previous 30-year period. Note that the average extreme cold temperatures area not the coldest recorded ever recorded (USDA Agricultural Research Service, 1990). Past weather records are a merely a guide to possible future temperatures; the changing nature of climate suggests that gardeners will see new low (and high) temperature extremes in Woodland Hills.
American Horticultural Heat-Zones
The American Horticultural Society (AHS) Plant Heat-Zone map shows average number of days a year over 86°F, the point at which plants begin to suffer heat damage.
Soil in Woodland Hills tends to be “hard, compact clay…the curse of most Valley gardeners” (Melinkoff, 1987).
temperature swings are wider and the air is drier than in coastal areas of Los Angeles. And, she said, all of that is good for some plants and not so good for others.
Hard, Compact Clay
The curse of most Valley gardeners, says Harrington, is the soil. "It's hard, compact clay soil," said Harrington, who operates Evergreen Garden Design and Maintenance out of her home in Canoga Park and teaches gardening classes at The Learning Tree, an adult education school in Chatsworth. "In some parts of Canoga Park, it's like digging in concrete,
Because our soil is so compacted, water puddles quickly. "Cold weather is more of a problem than hot," Harrington said. She said many of the plants in the Valley are native to subtropical areas and thus tolerate the cold poorly, especially when there is little rain.
In particular, Harrington said, there are cold pockets in Woodland Hills and Reseda. Summer heat can be compensated for with extra watering. "But heat and wind is the worst," she said. The combination can cause a plant to transpire water at a rate that is too rapid for it to survive, even when well watered.
City of Los Angeles. (2015) 2015 State of the Street Trees Report. Retrieved from http://bss.lacity.org/PDFs/SOTS_TREES_2015.pdf
Melinkoff, E. (1987, March 26). Savvy Gardeners Can Wring Pleasure From Valley's Clay. Los Angeles Times. (Nancy Harrington quotation). Retrieved from http://articles.latimes.com/1987-03-26/news/vw-464_1_gardening-classes
Weather Warehouse. (n.d.) Past Monthly Weather Data for Woodland Hills, CA [California] ("Canoga Park Pierce C") : JANUARY, 1949 - 2006. Retrieved from http://weather-warehouse.com/WeatherHistory/PastWeatherData_CanogaParkPierceC_WoodlandHills_CA_January.html
Woodland Hills, Los Angeles. (n.d.). In Wikipedia. Retrieved from https://en.wikipedia.org/wiki/Woodland_Hills,_Los_Angeles
Sources used for Figures
Figure 1. Woodland Hills and surrounding communities
Leggatt, J. (2015). Map of plant zones in Woodland Hills. Map compiled from data retrieved from http://www.sunset.com/garden/climate-zones/sunset-climate-zone-los-angeles-area
Figure 2. USDA plant hardiness map showing average extreme cold temperatures
Leggatt, J. (2015). Map showing average annual extreme cold temperatures in Woodland Hills. Compiled from data retrieved from http://planthardiness.ars.usda.gov/PHZMWeb/Images/300dpi/CA_S.jpg
Time Inc. Lifestyle Group. (n.d.). Sunset climate zones: Los Angeles region. Retrieved from http://www.sunset.com/garden/climate-zones/sunset-climate-zone-los-angeles-area
USDA Agricultural Research Service. (2012). Average Annual Extreme Minimum Temperature 1976-2005. (Interactive plant hardiness map). Retrieved from http://planthardiness.ars.usda.gov/PHZMWeb/InteractiveMap.aspx
Figure 3. AHS Plant Heat-Zone map shows average number of days a year over 86°F
American Horticultural Society. (n.d.) AHS Plant Heat Zone Map. Retrieved from http://www.ahs.org/gardening-resources/gardening-maps/heat-zone-map