One of the best tools that you have as gardeners to help us determine 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.

You should be able to figure out when it's possible to plant cosmos by using the USDA zone info for San Dimas.

Planting Calendar for Cosmos

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

Cosmos do well in some cold which means that you can plant them just a tiny bit earlier in the year than plants that are more sensitive to the cold.

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

Last Frost Date

On average the last frost has passed is on January 31 in San Dimas. It might get as low as 30°F during the coldest months of winter.

Keep in mind that USDA zone info for San Dimas is not always accurate and the actual date of last frost is different every year. Half of the time in San Dimas it frosts late in the year after January 31 so be sure to be ready to cover your cosmos if you have a surprise late frost.

USDA Zone Info for San Dimas

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 San Dimas

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