Do I Need to Cover Roses in Freezing Temps?

Climate

• Rose varieties are versatile plants, many of which grow in warm climates. Some species, however, thrive in cooler temperatures. Depending on the variety, roses will grow as far north as USDA Plant Hardiness Zone 4, where winter lows average minus 20 to minus 30 degrees F. In these climates, the cooler summer temperatures provide an ideal environment for flower performance.

Winter Damage

• Roses in severe climates, including USDA Plant Hardiness zones 4 and 5, can be damaged by cold, dry winter winds. The roots and canes can dry out and die if exposed. Often, a bush loses some or most of its canes, but comes back in spring from the roots or the bud union. Bud union and root damage can result from freeze and thaw cycles.

Dormancy

• Winter protection begins in late summer by preparing the bushes for winter dormancy. Bushes should not be fertilized after August 15 to avoid late flushes of tender stem growth that is vulnerable to cold damage. Likewise, deadheading spent blooms, which encourages new growth, should stop around October 1. These steps assure that the plant will slow down and go into dormancy as soon as freezing temperatures arrive.

Hilling Up

• In most climates, a 2-inch layer of mulch applied after a hard freeze is all that is needed to protect roses from winter damage. In more severe climates, the lower 10 to 12 inches of the canes can be covered with garden soil or loose compost, which is then allowed to freeze. Fallen leaves are piled on top of the mound of soil and evergreen boughs top it off. The mounds should be 18 to 24 inches tall. The pile is disassembled in early spring and the mounded soil is removed when it thaws.