Before planting it is a good idea to find your USDA Zone info to estimate your garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

In San Francisco you can determine when it's possible to plant primula by looking at the USDA zone info.

Planting Calendar for Primula

Frost tolerance for primula:	Very tolerant of frost.
When to plant:	Up to 7 weeks before last frost.

Primula can survive in cold weather which means that you can plant them earlier in the year than other plants that might not handle the cold.

The earliest that you can plant primula 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 primula and expect a good harvest is probably October. You probably don't want to wait any later than that or else your primula may not have a chance to really do well. You can get started a couple of weeks earlier by starting your primula indoors.

Last Frost Date

On average all chance of frost has passed is on January 31 in San Francisco. You can expect an average low temperature of 35°F in the coldest months of winter.

Remember that the actual date of last frost may not be accurate from year to year because it is based on the USDA zone info for San Francisco and it changes from year to year. Since half of the time in San Francisco you get a frost after January 31 be ready to protect your primula in the event of 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.