The USDA Zone info is a great tool for gardeners to help us figure out your gardening schedule. 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 it's possible to plant alternanthera is to refer to the USDA zone info for Napa.

Planting Calendar for Alternanthera

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

Since alternanthera are not cold tolerant you really should wait until after the last frost before you can plant them.

The earliest that you can plant alternanthera 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 alternanthera and expect a good harvest is probably September. You probably don't want to wait any later than that or else your alternanthera may not have a chance to really do well. If you are starting your alternanthera indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

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

Just be sure to remember that the actual date of last frost is not always accurate because it is based on the USDA zone info for Napa and it will vary from year to year. Since half of the time in Napa last frost occurs after February 15 be ready to cover your alternanthera if you have a late frost.

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.