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

By using the USDA zone info for Petaluma you will be able to estimate when it's a good idea to plant common hollyhock.

Planting Calendar for Common hollyhock

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

Since common hollyhock are moderately cold tolerant you can plant them a little earlier in the year than other plants that might not handle the cold.

The earliest that you can plant common hollyhock in Petaluma 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 common hollyhock and expect a good harvest is probably October. If you wait any later than that and your common hollyhock may not have a chance to fully mature. You can get started a little bit earlier by starting your common hollyhock indoors.

Last Frost Date

The average date of last frost is February 15 in Petaluma. It might get as low as 25°F during the coldest months of winter.

Since the USDA zone info for Petaluma is not always accurate the actual date of last frost can change quite a bit from year to year. Since half of the time in Petaluma it frosts late in the year after February 15 be ready to protect your common hollyhock if you have one of those late frosts.

USDA Zone Info for Petaluma

Here is the info for USDA Zone 9b.

Average Date of Last Frost (spring)	February 15
Average Date of First Frost (fall)	December 15
Lowest Expected Low	25°F
Highest Expected Low	30°F

This means that on a really cold year, the coldest it will get is 25°F. On most years you should be prepared to experience lows near 30°F.

Plants to Grow in Petaluma

You may be interested in your other planting guides for Petaluma.