Winter Care of Roses

Curtis E. Swift, Ph.D., Area Extension Agent (Horticulture)
Colorado State University Extension

Introduction

Hybrid tea, Floribunda, and Grandiflora roses, types most often grown in the Tri River Area, are very susceptible to winter dehydration These plants are usually grafted onto a root stock of a hardy wild-type rose. The graft tissue, like the canes, is susceptible to dehydration, and if not protected during the winter, may be killed. If tissue above the graft dies, the plant may still put out foliage and flowers, but these will be produced from tissue originating from buds below the root stock. The strange occurrence of off-color flowers on a plant that was advertised as having a different color bloom is often blamed on mutation. The problem in most cases, however, is due to lack of winter protection and death of the canes above the graft. Ramblers and climbers are relatively resistant to dehydration by winter winds are seldom require protection. In highly exposed areas, however, winter protection may be necessary.

Removing leaves and other plant debris from the area around the plant will help reduce insect and disease pest next year.

Winter Kill of Roots

The root system of roses, though normally cold hardy, is susceptible to winter dehydration. Without continual snow cover, winter winds, intense sunlight and low humid conditions constantly pull moisture from soil. If this moisture is not replaced by rain, snow, or supplemental irrigation, roots dry out and die. If too much moisture is lost from the root system, the plant dies. Mounding the plant with mulch or soil, or covering the roses with Styrofoam rose cones helps protect the plant from winter dehydration.

Mounding Roses

The ground normally freezes deep enough in Western Colorado by mid-December to allow the application of a mulch layer over the plant. The mound of mulch over the plant should be at least 10 to 12 inches high. If the soil is dry, water before applying the mulch layer. Wood chips, bark mulch or other loose materials are ideal as a rose mulch. Avoid the use of fine sawdust, rubbery leaves or other materials which tend to pack. In areas where mulch is a nesting site for rodents, soil can be used as the mulch material. This will need to be taken from another garden area so the root system of rose bush is not disturbed. If soil is taken from the rose bed, damage could occur to shallow roots. This mound of mulch or soil helps prevent soil moisture evaporation (root dehydration), dehydration of canes, and death of the graft union. This mulch layer also helps keep the ground cold reducing the chance of premature bud break in the spring.

Hybrid tea rose showing graft union
A hybrid tea rose showing exposed graft

hybrid tea rose mounded for winter protection
A hybrid tea rose properly mulched for the winter

Styrofoam-type rose protectors are available in some locales and on-line. When placed over the rose bush, they reflect heat from winter sun, protect the root system from continual freezing and thawing, and help prevent dehydration of canes and graft union. Hilling soil up against the side of protectors helps keep the wind from blowing these Styrofoam cones off the plants. Pruning the plant back may be necessary. If placed over the bush too early, premature growth may result. A brick or other weight placed on top of the rose cone will help keep it in place. Several web sites recommend the mounding of soil over the graft even when rose cones are used..

The use of tin cans, plastic or materials that absorb and hold heat should be avoided. The use of these materials is apt to result in dead plants by spring.

If soil or an organic material is used to mound the plant, carefully remove this over a period of several weeks in the spring to acclimate new developing shoots to the elements. If using a rose cone, keep it handy as it may be necessary to replace the cone on real cold spring nights to prevent frost damage to succulent tissue

Definitions:

Ramblers: Distinguished by very long and lithe shoots or canes - very vigorous producing shoots 12 to 15 feet long in a year. The leaves often persist well into winter. They bloom profusely in June and July (a few cultivars bloom later). These plants are generally winter hardy. Ramblers are not a very important rose today, having been replaced by the large flowered climbers. The fall in popularity of ramblers was mainly due to susceptibility to powdery mildew and its tendency to flower only once during the season.

Climbers: The most important climbers are roses that are bred as climbers such as Don Juan, America, Goldenshowers, Blaze, Blossom Time, Dortmund, Handel and Joseph's Coat. Climbers are more sensitive to winter damage than Ramblers. Ramblers are often grouped with climbers for simplicity.

  • Ramblers bloom on second year wood, consequently if they are killed all the way back in winter, they won't bloom that year. Most climbers, however, bloom on first year wood. (If climbers are killed back, they will still bloom). Ramblers and climbers that do not have protection from winter winds can benefit from some protection. Take the canes off the trellis and remove all dead and damaged canes. Bend remaining canes to the ground, and stake them to hold them down. Cover the canes with a couple inches of soil. Additional mulch such as hay, straw, or leaves can be added for further protection. Hold this loose mulch down with pine boughs, chicken wire, or an occasional board to keep the straw, hay or leaves from blowing away. Remove this mulch in the spring as soon as the growth resumes and put the plant back on the trellis.

Hybrid Tea Rose: The most common rose sold by nurseries - - bears one bloom per stem (usually). Fragrant roses - - can be damaged when temperatures reach +10 degrees or lower - a cross between Tea and Hybrid Perpetual.

Floribunda: Once known as Hybrid Polyanthas - - varieties that bloom in summer and fall - - These plants are often as tall as average Hybrid Tea.

Grandiflora: A name given to hybrids of Floribunda and Hybrid Tea Roses (crosses) in which the blooms approach the Hybrid Tea in size and form - - flowers borne in clusters on main stems - - Clusters consist of fewer blooms than usual in Floribundas - - bloom all summer into autumn - - damaged at 10 degrees F. or below.

Placed on Internet: 12/18/2000; Updated April 30, 2010