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.

You should be able to determine when it's a good idea to plant sunflowers by referring to the USDA zone info for Sunnyvale.

Planting Calendar for Sunflowers

Frost tolerance for sunflowers:	Not tolerant of frost.
When to plant:	After the last frost when the weather gets warmer.

Sunflowers are not cold tolerant which tells us that it is necessary to wait until it warms up after the last frost before you can plant them.

The earliest that you can plant sunflowers in Sunnyvale 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. If you wait any later than that and your sunflowers may not have a chance to really do well. If you are starting your sunflowers indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

On average the last frost has passed is on February 15 in Sunnyvale. You should expect an average low temperature of 25°F in the coldest months of winter.

Just be sure to remember that the actual date of last frost is an average because it is based on the USDA zone info for Sunnyvale and it will vary from year to year. Since half of the time in Sunnyvale last frost occurs after February 15 be ready to protect your sunflowers if you have one of those late frosts.

USDA Zone Info for Sunnyvale

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 Sunnyvale

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