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 making a decision about when to plant zinnia is to use the USDA zone info for Napa.

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 a bad idea to plant zinnia until after the last frost because they are not cold tolerant.

The earliest that you can plant zinnia in Napa 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. Any later than that and your zinnia may not have a chance to really do well. You can get started a few weeks earlier by starting your zinnia indoors.

Last Frost Date

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

It's important to remember that USDA zone info for Napa is an average and the actual date of last frost will vary from year to year. Half of the time in Napa you get a frost after February 15 so make sure that you are ready to protect your zinnia if you have one of those late frosts.

USDA Zone Info for Napa

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 Napa

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