The USDA Zone info is a great tool for gardeners to help us estimate your gardening schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

A common way of determining when it's the best time to plant primula is to look at the USDA zone info for Corona.

Planting Calendar for Primula

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

Primula are one of those plants that can tolerate quite a bit of cold weather which means that you can plant them much earlier than more sensitive plants.

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

Last Frost Date

In Corona the average date of last frost happens on February 15. It might get as low as 25°F during the coldest months of winter.

Keep in mind that the actual date of last frost is an average because it is based on the USDA zone info for Corona and it will vary from year to year. Since half of the time in Corona you get surprised by a frost after February 15 be ready to cover your primula in the event of one of those late frosts.

USDA Zone Info for Corona

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 Corona

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