One of the best tools that you have as gardeners to help us estimate 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 Portland can be reffered to in order to estimate when it's the best time 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 can survive in pretty solid cold which tells us that you can plant them much earlier in the year than other plants that might not handle the cold.

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

The last month that you can plant primroses and expect a good harvest is probably September. Any later than that and your primroses may not have a chance to really do well. Starting your primroses indoors is a great way to get them started a few weeks earlier.

Last Frost Date

The average date of last frost is March 15 in Portland. It might get as low as 15°F during the coldest months of winter.

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 Portland and it is different every year. Since half of the time in Portland last frost occurs after March 15 be ready to cover your primroses in the event of a late frost.

USDA Zone Info for Portland

Here is the info for USDA Zone 8b.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	15°F
Highest Expected Low	20°F

This means that on a really cold year, the coldest it will get is 15°F. On most years you should be prepared to experience lows near 20°F.

Plants to Grow in Portland

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