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.

One way of figuring out when you can plant dahlia is to use the USDA zone info for Rohnert Park.

Planting Calendar for Dahlia

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

Dahlia require warm weather which tells us that you really should wait until it warms up after all chance of frost has passed before you can plant them.

The earliest that you can plant dahlia in Rohnert Park 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 dahlia and expect a good harvest is probably September. If you wait any later than that and your dahlia may not have a chance to grow to maturity. If you are starting your dahlia indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

In Rohnert Park the average date of last frost happens on February 15. It might get as low as 25°F during the coldest months of winter.

Since the USDA zone info for Rohnert Park is not always accurate the actual date of last frost changes from year to year. Since half of the time in Rohnert Park you get surprised by a frost after February 15 be ready to cover your dahlia if you have a surprise late frost.

USDA Zone Info for Rohnert Park

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 Rohnert Park

You may be interested in your other planting guides for Rohnert Park.