Can Primrose Tolerate Frost?

Primrose Varieties

• The genus Primula is made up of more than 450 distinct primrose species, according to the American Primrose Society. Wild primrose species can be found in a wide range of habitats, from the cliff-dwelling “verticillata” of the Arabian desert to the high arctic “egaliksensis” that grows in soggy hollows above the permafrost. Many types of primrose adapt well to the typical northern garden environment, even those native to more extreme conditions, according to botany professor John Richards in his book “Primula.” Primroses are mostly perennials, but some are biennials, and a few are true annuals. “Vulgaris,” the common primrose, is often treated as an annual but is a true perennial.

Growing Conditions

• Because there is such a variety of primroses, ideal growing conditions vary somewhat. In general, however, primroses dislike extreme temperatures. Most species are native to regions where they’re covered in snow while dormant, which keeps them insulated and protects them from deep freeze. Most primroses prefer cool, humid environments. Very few have adapted to hot, dry climates, and tend to suffer during long, hot dry spells. Consequently, most varieties bloom throughout the spring and die back in the summer to escape the heat. A moderate environment is the key to successfully growing nearly all primrose species, according to Professor Richards, even the few that are considered difficult to cultivate outside their native environments.

Frost Tolerance

• When in bloom, most primrose varieties grown in the ground can tolerate a short frost cycle without being covered. Your spring blooms aren't likely to suffer damage from one or two nights of irregular temperatures reaching no lower than 23 degrees Fahrenheit. However, it’s best to protect your primroses anytime the temperature drops below freezing by covering your blooming plants with sheets or blankets topped with plastic and anchored by heavy stones, especially if precipitation is involved. It’s also beneficial to cover your primroses with newspaper or fern fronds during the winter. When adequately covered, many in-ground primrose species can safely remain outside in regions that endure heavy precipitation and moderate to extreme freeze/thaw cycles.

Considerations

• In places where winters are consistently very cold, many in-ground primrose varieties cannot overwinter outside. According to Professor Richards, species that successfully endure cold winters with a consistent freeze/thaw cycle often die in areas where winters are long and very cold. All pot-grown primroses, on the other hand, should be brought inside before the first frost. Likewise, you should also bring your blooming potted primrose plants inside in the event of a spring frost. While hardier varieties planted in containers aren’t likely to sustain damage after a night of mild frost, less hardy varieties — including the little potted hybrids commonly available in grocery stores — should be kept in frost-free conditions.