One of the first steps you take when you are estimating your gardening schedule is find your 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 USDA zone info for Petaluma can be used to determine when to plant sunflowers.

Planting Calendar for Sunflowers

Frost tolerance for sunflowers:	Not tolerant of frost.
When to plant:	After the last frost has passed.

It's not a good idea to plant sunflowers until after the last frost when the weather gets warmer because they require warm weather.

The earliest that you can plant sunflowers in Petaluma is March. However, you really should wait until April if you don't want to take any chances.

The last month that you can plant sunflowers and expect a good harvest is probably September. Any later than that and your sunflowers may not have a chance to fully mature. If you are starting your sunflowers indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

In Petaluma the average date of last frost happens on February 15. In the coldest months of winter you should expect an average low temperature of 25°F.

Keep in mind that USDA zone info for Petaluma may not be accurate from year to year and the actual date of last frost is different every year. Since half of the time in Petaluma you get a frost after February 15 be ready to protect your sunflowers in the event of a late frost.

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.