How to Keep Primroses From Freezing

Reduce watering frequency gradually as the first expected fall frost date approaches. Allow the soil to dry between each watering. Minimal water combined with shorter days and cooler temperatures forces the primroses into a state of dormancy, which allows them to withstand winter freezes.

Mulch around the plants with a 2-inch layer of straw mulch. The mulch insulates the primrose roots and protects them from freeze damage. Add more mulch to cover the plants once they go completely dormant and the foliage begins to die back.

Place a cold frame over the plants in areas with severe winter freezing. A cold frame consists of a glass-topped box. Sunlight enters the glass top and warms the air inside the frame so the plants don't experience the full brunt of winter freezing. Cold frames may require venting on sunny days so the plants don't overheat.

Cover flowering plants with a frost blanket if a late spring frost is predicted after the primroses have begun to put on new growth. The blanket keeps the frost from settling on the foliage and damaging the tender new growth.