The USDA Zone info is a great tool for gardeners to help us estimate your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

A way of figuring out when it's a good idea to plant black radish is to consult the USDA zone info for Portola Valley.

Planting Calendar for Black radish

Frost tolerance for black radish:	Tolerant of some frost.
When to plant:	Up to 5 weeks before last frost.

Black radish do ok in a little bit of cold which tells us that you can plant them a little bit earlier in the year than more sensitive plants.

The earliest that you can plant black radish in Portola Valley is January. However, you really should wait until February if you don't want to take any chances.

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

Since the USDA zone info for Portola Valley may not be accurate from year to year the actual date of last frost can change quite a bit from year to year. Half of the time in Portola Valley you get a frost after January 31 so be sure to be ready to cover your black radish 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.