Before planting it is a good idea to find your USDA Zone info to determine 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.

It's possible to figure out when to plant delphinium by referring to the USDA zone info for San Francisco.

Planting Calendar for Delphinium

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

Delphinium are barely cold tolerant which tells us that you can plant them slightly earlier than plants that are more sensitive to the cold.

The earliest that you can plant delphinium 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 delphinium and expect a good harvest is probably September. If you wait any later than that and your delphinium may not have a chance to grow to maturity. Starting your delphinium indoors is a great way to get them started a few weeks earlier.

Last Frost Date

On average the last frost has passed is on January 31 in San Francisco. It might get as low as 35°F during the coldest months of winter.

Since the USDA zone info for San Francisco may not be accurate from year to year the actual date of last frost is different every year. Since half of the time in San Francisco you get surprised by a frost after January 31 be ready to protect your delphinium in the event of one of those late frosts.

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.