One of the first steps you take when you are making a decision about your gardening schedule is find your 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.

By reviewing the USDA zone info for San Bernardino you should be able to estimate when it's possible to plant primula.

Planting Calendar for Primula

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

Since primula do well in cold you can plant them quite a bit earlier in the year than more sensitive plants.

The earliest that you can plant primula in San Bernardino 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. If you wait any later than that and your primula may not have a chance to grow to maturity. If you are starting your primula indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

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

Keep in mind that the actual date of last frost is not always accurate because it is based on the USDA zone info for San Bernardino and it changes from year to year. Half of the time in San Bernardino you get a frost after February 15 so always be ready to cover your primula in the event of a late frost.

USDA Zone Info for San Bernardino

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 San Bernardino

You may be interested in your other planting guides for San Bernardino.