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.

The USDA zone info for Napa can be reviewed to figure out when it's possible to plant iresene.

Planting Calendar for Iresene

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

You really shouldn't plant iresene until after the last frost because they require warm weather.

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

Last Frost Date

On average the last frost when the weather gets warmer is on February 15 in Napa. You can expect an average low temperature of 25°F in the coldest months of winter.

Since the USDA zone info for Napa is not always accurate the actual date of last frost changes from year to year. Half of the time in Napa you get a frost after February 15 so just be sure to be ready to cover your iresene in the event of 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.