The USDA Zone info is a great tool for gardeners to help us figure out 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.

A common way of determining when it's a good idea to plant iresene is to consult the USDA zone info for Portola Valley.

Planting Calendar for Iresene

Frost tolerance for iresene:	Not tolerant of frost.
When to plant:	After the last frost.

Since iresene do not do well in cold weather it's important to wait until after all chance of frost has passed before you can plant them.

The earliest that you can plant iresene 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 iresene and expect a good harvest is probably September. If you wait any later than that and your iresene may not have a chance to fully mature. Starting your iresene indoors is a great way to get them started a little bit earlier.

Last Frost Date

The average date of last frost is January 31 in Portola Valley. In the coldest months of winter you should expect an average low temperature of 30°F.

Since the USDA zone info for Portola Valley is an average the actual date of last frost is different every year. Half of the time in Portola Valley it frosts late in the year after January 31 so always be ready to protect your iresene in the event of a 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.