One of the best tools that you have as gardeners to help us figure out your gardening schedule is the USDA zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The first chance to plant dahlias in Portola Valley can be estimated by reviewing the USDA zone info.

Planting Calendar for Dahlias

Frost tolerance for dahlias:	Not tolerant of frost.
When to plant:	After all chance of frost has passed.

Since dahlias are not cold tolerant it's important to wait until after the last frost before you can plant them.

The earliest that you can plant dahlias in Portola Valley 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 dahlias and expect a good harvest is probably September. If you wait any later than that and your dahlias may not have a chance to really do well. Starting your dahlias indoors is a great way to get them started a little bit earlier.

Last Frost Date

In Portola Valley the average date of last frost happens on January 31. It might get as low as 30°F during the coldest months of winter.

Keep in mind that the actual date of last frost may not be accurate from year to year because it is based on the USDA zone info for Portola Valley and it can change quite a bit from year to year. Since half of the time in Portola Valley there is a last frost after January 31 be ready to cover your dahlias if you have one of those late frosts.

USDA Zone Info for Portola Valley

Here is the info for USDA Zone 10a.

Average Date of Last Frost (spring)	January 31
Average Date of First Frost (fall)	December 15
Lowest Expected Low	30°F
Highest Expected Low	35°F

This means that on a really cold year, the coldest it will get is 30°F. On most years you should be prepared to experience lows near 35°F.

Plants to Grow in Portola Valley

You may be interested in your other planting guides for Portola Valley.