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.

The USDA zone info for San Jose should be used to determine when to plant hardy asters.

Planting Calendar for Hardy Asters

Frost tolerance for hardy asters:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Hardy Asters are barely cold tolerant which tells us that you can get them planted just a bit earlier than more sensitive plants.

The earliest that you can plant hardy asters in San Jose 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 hardy asters and expect a good harvest is probably September. Any later than that and your hardy asters may not have a chance to fully mature. If you are starting your hardy asters indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

In San Jose the average date of last frost happens on February 15. You should expect an average low temperature of 25°F in the coldest months of winter.

Remember that USDA zone info for San Jose may not be accurate from year to year and the actual date of last frost is different every year. Since half of the time in San Jose you get surprised by a frost after February 15 be ready to cover your hardy asters if you have a 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.