One of the best tools that you have as gardeners to help us determine your gardening schedule is the USDA zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

The best time to plant alternaria in Napa can be determined by checking out the USDA zone info.

Planting Calendar for Alternaria

Frost tolerance for alternaria:	Not tolerant of frost.
When to plant:	After the last frost has passed.

You should not plant alternaria until after the last frost when the weather gets warmer because they are not cold tolerant.

The earliest that you can plant alternaria 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 alternaria and expect a good harvest is probably September. If you wait any later than that and your alternaria may not have a chance to grow to maturity. You can get started a few weeks earlier by starting your alternaria indoors.

Last Frost Date

On average the last frost has passed is on February 15 in Napa. You should expect an average low temperature of 25°F in the coldest months of winter.

It's important to remember that the actual date of last frost is an average because it is based on the USDA zone info for Napa and it changes from year to year. Half of the time in Napa you get surprised by a frost after February 15 so make sure that you are ready to cover your alternaria 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.