One of the first steps you take when you are determining 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.

It's a good idea to estimate when it's the best time to plant primula by reviewing the USDA zone info for Riverside.

Planting Calendar for Primula

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

Primula do well in a bit of cold which means that you can plant them much earlier in the year than other frost tender plants.

The earliest that you can plant primula in Riverside 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. Any later than that and your primula may not have a chance to really do well. You can get started a couple of weeks earlier by starting your primula indoors.

Last Frost Date

On average all chance of frost has passed is on February 15 in Riverside. 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 an average because it is based on the USDA zone info for Riverside and it is different every year. Half of the time in Riverside there is a last frost after February 15 so make sure that you are prepared to cover your primula if you have a late frost.

USDA Zone Info for Riverside

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 Riverside

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