Shrub Roses and Old Garden Roses are gaining in popularity across the northern tier of the United States as gardeners realize that these plants often provide excellent floral quality in combination with disease tolerance and winter hardiness. By planting these roses, gardeners can minimize pesticide use and eliminate the labor-intensive job of protecting roses from low winter temperatures.

Along with a resurgence of interest in these roses has come the realization that there is little published information comparing the growth and performance of Shrub Rose and Old Garden Rose cultivars. To provide comparative data for some of these cultivars, the Woody Ornamental Research Project at the Minnesota Landscape Arboretum conducted an evaluation program of the roses in the Arboretum's Shrub Rose Garden and research nurseries, and in a private garden near the Arboretum.

The Minnesota Landscape Arboretum is located in Chanhassen, Minnesota, a western suburb of the Minneapolis-St. Paul metropolitan area. The Shrub Rose Garden is a collection of approximately 200 hardy roses, most of which are considered Old Garden Roses or Shrub Roses. Table 1 shows the distribution of evaluated cultivars across the 23 rose classes represented.

Among the Old Garden Roses can be found the Gallicas, Damasks, Albas, Centifolias, and Moss Roses. These are roses that were in existence before the repeat-flowering China Rose was introduced into Europe in the late 1700s. The blending of the Old Garden Roses and the China Roses revolutionized the development of roses, giving them the ability to bloom repeatedly through a growing season. This eventually led to the development of the modern-day Hybrid Teas and Floribundas.

The Old Garden Roses differ from Hybrid Teas and Floribundas in several ways. In their growth habit, for instance, the old roses are often larger and more branched than the small, upright forms of Hybrid Teas and Floribundas.

Old Garden Roses are grown for their wide variety of mature, open flower forms, while Hybrid Tea and Floribunda flowers are considered most attractive when flower buds are only partially open. The range of flower color among the Old Garden Roses is smaller, and most cultivars within this group have only one season of bloom. This one season of bloom is often seen as a disadvantage, but in their one flush of bloom, Old Garden Roses often produce as many flowers as repeat-flowering cultivars do across their extended bloom period.

The arrangement of tightly packed petals which gives the flower a "quartered" appearance, along with a green "eye," is a common flower form among Old Garden Roses.

The Old Garden Roses are also noted for their fragrance. Among the more modern roses, fragrance is variable.

Because the Old Garden Roses are less demanding of soil conditions and have higher levels of disease resistance and winter hardiness, they are considered more carefree than Hybrid Tea and Floribunda roses.

Among the Old Garden Roses are also groups that resulted from early attempts at hybridizing the Gallicas, Damasks, Albas, Centifolias, and Moss Roses with the China Rose. These rose classes include the Chinas, Portlands, Bourbons, Hybrid Perpetuals, and Teas. Like their China Rose ancestors, these roses have glossier foliage, fewer thorns, and some potential for repeat bloom. They usually retain the floral characteristics and shrub form of their old rose ancestors.

Many other classes of roses are represented in the Minnesota Landscape Arboretum's Shrub Rose Garden. These range from the Species, or wild roses, to the few Floribundas hardy enough to survive without winter protection. Between these extremes are other classes of roses that are often collectively called "shrub roses." These resulted from the blending of the Old Garden Roses, Hybrid Teas, or Floribundas with Species Roses and their hybrids.

Some Shrub Roses will rebloom during the growing season, but it is still difficult for them to rival the rebloom of the Hybrid Teas and Floribundas. The blending of Species Rose flower form with that of the other rose classes tends to result in a mass of semi-double, informal flowers among the Shrub Rose cultivars. More often than not, Shrub Roses are larger and more branched than Hybrid Teas and Floribundas.

During a multi-year study, the results of which form the basis of this publication, roses were evaluated for floral traits, bloom pattern, plant size and habit, disease and insect tolerance, and winter injury. Field evaluations were conducted from 1989 through 1992. Controlled lab studies measuring mid-winter hardiness of rose canes were done over several winters between 1989 and 1994.

It should be emphasized that plant performance is always site- related. Variations in climate, soil conditions, races of pathogens and insects present, and cultural practices all affect the growth and performance of plants. The information in this publication measures performance of hardy roses at the Minnesota Landscape Arboretum, and should be interpreted only as an indication of how plants might perform in gardens in the Upper Midwest and Canada.

The tables in this publication list rose cultivars alphabetically within each rose class. Classification and nomenclature follow that of Modern Roses 10.¹

¹ Modern Roses 10, T. Cairns, ed. American Rose Society, Shreveport, Louisiana. 1993.

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