One of the best tools that you have as gardeners to help us determine your gardening schedule is the USDA zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

The earliest that you can plant phlox in San Francisco can be estimated by checking out the USDA zone info.

Planting Calendar for Phlox

Frost tolerance for phlox:	Tolerant of some frost.
When to plant:	Up to 5 weeks before last frost.

You can plant phlox just a bit earlier in the year because they do well in moderate cold.

The earliest that you can plant phlox in San Francisco is January. However, you really should wait until February if you don't want to take any chances.

The last month that you can plant phlox and expect a good harvest is probably October. Any later than that and your phlox may not have a chance to grow to maturity. Starting your phlox indoors is a great way to get them started a few weeks earlier.

Last Frost Date

On average the last frost when the weather gets warmer is on January 31 in San Francisco. You should expect an average low temperature of 35°F in the coldest months of winter.

Since the USDA zone info for San Francisco is an average the actual date of last frost can change quite a bit from year to year. Half of the time in San Francisco you get surprised by a frost after January 31 so make sure that you are prepared to protect your phlox if you have a surprise late frost.

USDA Zone Info for San Francisco

Here is the info for USDA Zone 10b.

Average Date of Last Frost (spring)	January 31
Average Date of First Frost (fall)	December 15
Lowest Expected Low	35°F
Highest Expected Low	40°F

This means that on a really cold year, the coldest it will get is 35°F. On most years you should be prepared to experience lows near 40°F.

Plants to Grow in San Francisco

You may be interested in your other planting guides for San Francisco.