One of the best tools that you have as gardeners to help us determine your gardening schedule is the 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 earliest that you can plant begonias in Portola Valley should be determined by referring to the USDA zone info.

Planting Calendar for Begonias

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

It's probably a bad idea to plant begonias until after all chance of frost has passed because they are not cold tolerant.

The earliest that you can plant begonias 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 begonias and expect a good harvest is probably September. You probably don't want to wait any later than that or else your begonias may not have a chance to grow to maturity. If you are starting your begonias indoors then you might be able to get away with starting them a couple of weeks 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.

Remember 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 changes from year to year. Since half of the time in Portola Valley you get surprised by a frost after January 31 be ready to cover your begonias in the event of a surprise late frost.

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.