What Temperature Will Kill Pansies? Everything You Need to Know

<p>v_zaitsev / Getty Images</p>

v_zaitsev / Getty Images

When winter begins, gardeners everywhere plant pansies. These early annuals are beloved for their tolerance of cold temperatures and big, brightly colored blooms with their characteristic blotch. Pansies are also planted in autumn, bringing late color to the garden through winter months or even overwintered to bloom again in early spring.

How much cold these garden favorites will survive depends on your specific climate and growing conditions.

Find out how much cold is too cold, how to protect your pansies from snow and freezing temperatures, and ways to revive them when winter weather leaves them looking puny.



Winter Pansies

Some pansy varieties are known as Ice or Winter pansies and are set out in autumn. Winter pansies bloom throughout autumn, winter, and spring in warmer climates and in early spring in colder climates.



What Temperature Will Kill Pansies?

Both soil and air temperature affect pansy health. Other growing conditions play a role in determining how much cold they can survive. Air temperature below 25°F for just a few hours can send them into dormancy and below 20°F can cause plants to die back completely.

Frozen soil and drying winter winds are factors contributing to plant loss. Pansies kept in warm sunshine with some protection for the roots are more apt to survive lower temperatures for short periods.

How Do You Prepare Pansies for Cold Temperatures

Pansies grow best in soil temperatures ranging from 45 to 65 degrees F. Ideal air temperature ranges from 40°F at night to 60°F during the day. For bedding plants, choose a southeast location that receives plenty of morning sun. Cold overnight temperatures may cause plants to droop but warmth from winter sun perks them up again.

Buildings, stone walls, and foundation shrubs protect from cold, desiccating winds. Move potted plants into a garage, porch, or other sheltered location when heavy frost or an extended freeze is forecast.

A thick layer of straw mulch retains moisture to help roots sustain cold soil. Insulating row covers prevent foliage and blooms from freezing when the mercury drops below 32°F

How to Care for Pansies Through Winter

Care during winter months generally applies to pansy varieties set out in autumn. Follow these tips to keep them healthy and blooming.

  • Keep pansies in a location that receives at least six hours of sunlight daily.

  • Check soil regularly for moisture. Pansies require consistently moist soil so you'll need to water when rainfall or snow cover is insufficient. Potted plants require more frequent watering.

  • Feed potted plants once every two weeks and bedding plants monthly with an all-purpose fertilizer high in phosphorous such as an NPK 15-30-15.

  • Consistently deadhead spent blooms, pinching off flowers at the base.

  • Mulch with a thick layer of straw.

  • In case of extended frost or freezing protect bedding plants with row covers and move potted plants to a sheltered location.

Will Pansies Come Back After a Freeze?

Pansies grown in southern climates are more likely to survive an occasional freeze and even bounce back when covered with snow. Cold air is less likely to cause dieback than extended periods of frozen ground. Winter pansies can sometimes revive even when frozen solid.

Frozen soil affects the roots' ability to take up water and nutrients. When starved too long plants eventually die. Pansies are better able than most annuals to withstand these adverse conditions and once temperatures warm a bit and plants receive sufficient sun, they begin to form new buds.



Tip

Whether planted in autumn or in early spring, pansies are grown as annuals and replanted every year. Some spring-planted types rebloom in autumn once temperatures drop into the 60°F range during the day with cooler nights. In climates where the ground doesn't freeze, autumn-planted pansies often last through until early summer of the following year when they finally succumb to summer heat.

Occasionally a pansy pops up in a flower bed or pot, sometimes a year or two after the original planting. These 'volunteers' lack vigor and are usually short-lived.



How Do You Revive Pansies After Frost?

Heavy frosts cause flowers to wilt and foliage to take on a grayish, wilted appearance. Remove damaged flowers and foliage that's turned mushy or black. Make sure the soil is kept moist and prune back lightly at first.

Once the danger of frost is past and plants begin to put out new growth, any damaged foliage remaining should be removed. Move potted plants to a location that receives bright morning sun and feed with a fertilizer high in phosphorous.

Read the original article on The Spruce.