The USDA Zone info is a great tool for gardeners to help us figure out your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

You will be able to figure out when to plant petunias by referring to the USDA zone info for San Francisco.

Planting Calendar for Petunias

Frost tolerance for petunias:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Petunias do ok in moderate cold which tells us that you can get them planted just a bit earlier than other plants that might not handle the cold.

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

The last month that you can plant petunias and expect a good harvest is probably September. You probably don't want to wait any later than that or else your petunias may not have a chance to really do well. If you are starting your petunias indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

In San Francisco the average date of last frost happens on January 31. It might get as low as 35°F during the coldest months of winter.

Keep in mind 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 will vary from year to year. Since half of the time in San Francisco there is a last frost after January 31 be ready to cover your petunias 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.