One of the best tools that you have as gardeners to help us estimate your gardening schedule is the USDA zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

One way of determining when to plant dahlia is to consult the USDA zone info for San Jose.

Planting Calendar for Dahlia

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

Since dahlia require warm weather you must wait until after all chance of frost has passed before you can plant them.

The earliest that you can plant dahlia in San Jose is March. However, you really should wait until April if you don't want to take any chances.

The last month that you can plant dahlia and expect a good harvest is probably September. You probably don't want to wait any later than that or else your dahlia may not have a chance to fully mature. You can get started a few weeks earlier by starting your dahlia indoors.

Last Frost Date

On average the last frost when the weather gets warmer is on February 15 in San Jose. In the coldest months of winter you should expect an average low temperature of 25°F.

Always keep in mind that USDA zone info for San Jose is just an average and the actual date of last frost will vary from year to year. Since half of the time in San Jose there is a last frost after February 15 be ready to cover your dahlia in the event of one of those late frosts.

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.