The USDA Zone info is a great tool for gardeners to help us estimate your gardening schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

It's a good idea to determine when it's possible to plant four-o-clock flower by using the USDA zone info for Portola Valley.

Planting Calendar for Four-o-clock flower

Frost tolerance for four-o-clock flower:	Not tolerant of frost.
When to plant:	After the last frost when the weather gets warmer.

It's a bad idea to plant four-o-clock flower until after all chance of frost has passed because they do not do well in cold weather.

The earliest that you can plant four-o-clock flower 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 four-o-clock flower and expect a good harvest is probably September. Any later than that and your four-o-clock flower may not have a chance to grow to maturity. You can get started a little bit earlier by starting your four-o-clock flower indoors.

Last Frost Date

On average all chance of frost has passed is on January 31 in Portola Valley. It might get as low as 30°F during the coldest months of winter.

Always keep in mind that USDA zone info for Portola Valley is an average and the actual date of last frost will vary from year to year. Since half of the time in Portola Valley it frosts late in the year after January 31 be ready to protect your four-o-clock flower in the event of 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.