AMES, Iowa — All roses need some attention going into winter, and there are many methods to provide winter protection. Horticulturists with Iowa State University Extension and Outreach offer suggestions for preparing roses for Iowa’s winter weather. Contact Hortline by emailing firstname.lastname@example.org or calling 515-294-3108 to ask the specialists additional pre-winter gardening questions.
Most hybrid tea, grandiflora, floribunda and other modern roses require protection during the winter months. Low temperatures and rapid temperature changes in winter can severely injure and sometimes kill unprotected modern roses. (Most old garden roses possess excellent cold hardiness and don’t require winter protection.)
Hilling or mounding soil over the base of each plant is an excellent way to protect hybrid tea, grandiflora and floribunda roses. Begin by removing fallen leaves and other debris from around each plant. Removal of diseased plant debris will help reduce disease problems next season. Then, loosely tie the canes together with twine to prevent the canes from being whipped by strong winds. Next, cover the bottom 10 to 12 inches of the rose canes with soil. Place additional material, such as straw or leaves, over the mound of soil. A small amount of soil placed over the straw or leaves should hold these materials in place.
Prepare hybrid tea, grandiflora and floribunda roses for winter after the plants have been hardened by exposure to several nights of temperatures in the low to mid-20s. Normally, this is early November in northern Iowa, mid-November in central areas and late November in southern counties.
Rose cones by themselves generally don’t provide adequate protection. Additional insulating material is necessary. Prune the rose bush to allow it to fit under the cone. Then mound soil over the base of the plant, covering the bottom 6 to 8 inches of the rose canes. Place the cone over the rose, securing the cone with bricks or soil. If no holes are provided at the top of the cone, puncture several holes around the top to provide ventilation. Air temperatures inside the cones may get quite warm on sunny, mild winter days without ventilation holes.
A rose growing in a pot may be destroyed if the potted rose is left on a deck or patio over winter. Potting soil temperatures in containers left above ground are likely to get extremely cold, damaging or destroying the roots of the rose.
To protect a potted rose, dig a hole in the ground in a sheltered location. Set the pot in the ground and then place soil around the pot. Place additional soil over the rose covering the bottom 6 to 8 inches of the rose canes.
Potted miniature roses also can be brought indoors before a hard freeze in fall and placed in a south or west-facing window and maintained as a houseplant.