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 USDA zone info for Napa should be looked at to figure out when to plant primroses.

Planting Calendar for Primroses

Frost tolerance for primroses:	Very tolerant of frost.
When to plant:	Up to 7 weeks before last frost.

Primroses are one of those plants that can tolerate quite a bit of cold weather which means that you can get them planted much earlier than other frost tender plants.

The earliest that you can plant primroses in Napa is January. However, you really should wait until February if you don't want to take any chances.

The last month that you can plant primroses and expect a good harvest is probably October. Any later than that and your primroses may not have a chance to really do well. If you are starting your primroses indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

In Napa the average date of last frost happens on February 15. 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 is different every year. Since half of the time in Napa you get a frost after February 15 be ready to protect your primroses in the event of 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.