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 earliest that you can plant primroses in Rialto can be determined by referring to the USDA zone info.

Planting Calendar for Primroses

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

Since primroses do well in cold you can plant them a lot earlier in the year than other plants that might not handle the cold.

The earliest that you can plant primroses in Rialto 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. You probably don't want to wait any later than that or else your primroses may not have a chance to grow to maturity. You can get started a few weeks earlier by starting your primroses indoors.

Last Frost Date

On average all chance of frost has passed is on January 31 in Rialto. You should expect an average low temperature of 30°F in the coldest months of winter.

Remember that the actual date of last frost is just an average because it is based on the USDA zone info for Rialto and it can change quite a bit from year to year. Since half of the time in Rialto you get surprised by a frost after January 31 be ready to protect your primroses if you have a late frost.

USDA Zone Info for Rialto

Here is the info for USDA Zone 10a.

Average Date of Last Frost (spring)	January 31
Average Date of First Frost (fall)	December 15
Lowest Expected Low	30°F
Highest Expected Low	35°F

This means that on a really cold year, the coldest it will get is 30°F. On most years you should be prepared to experience lows near 35°F.

Plants to Grow in Rialto

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