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

The USDA zone info for San Jose can be reffered to in order to figure out when it's possible to plant onions.

Planting Calendar for Onions

Frost tolerance for onions:	Very tolerant of frost.
When to plant:	Up to 7 weeks before last frost.

Since onions are one of those plants that can tolerate quite a bit of cold weather you can plant them much earlier in the year than other plants that might not handle the cold.

The earliest that you can plant onions in San Jose 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 onions and expect a good harvest is probably October. Any later than that and your onions may not have a chance to fully mature. Starting your onions indoors is a great way to get them started a few weeks earlier.

Last Frost Date

The average date of last frost is February 15 in San Jose. In the coldest months of winter you can expect an average low temperature of 25°F.

Since the USDA zone info for San Jose is not always accurate the actual date of last frost can change quite a bit from year to year. Since half of the time in San Jose there is a last frost after February 15 be ready to protect your onions if you have a surprise late frost.

USDA Zone Info for San Jose

Here is the info for USDA Zone 9b.

Average Date of Last Frost (spring)	February 15
Average Date of First Frost (fall)	December 15
Lowest Expected Low	25°F
Highest Expected Low	30°F

This means that on a really cold year, the coldest it will get is 25°F. On most years you should be prepared to experience lows near 30°F.

Plants to Grow in San Jose

You may be interested in your other planting guides for San Jose.