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 will be able to determine when to plant zinnia by looking at the USDA zone info for Atherton.

Planting Calendar for Zinnia

Frost tolerance for zinnia:	Not tolerant of frost.
When to plant:	After the last frost when the weather gets warmer.

It's probably a bad idea to plant zinnia until after the last frost has passed because they require warm weather.

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

Last Frost Date

In Atherton the average date of last frost happens on February 15. In the coldest months of winter you should expect an average low temperature of 25°F.

Remember that USDA zone info for Atherton may not be accurate from year to year and the actual date of last frost can change quite a bit from year to year. Half of the time in Atherton you get a frost after February 15 so be sure to be ready to protect your zinnia if you have a surprise late frost.

USDA Zone Info for Atherton

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 Atherton

You may be interested in your other planting guides for Atherton.