Large, small, climbing or scrambling, all roses are technically shrubs. However, the term "shrub rose" has come to mean a rose that is used in the landscape in the same way as other shrubby plants, like yews, rhododendrons or hydrangeas. A shrub rose can be grown alone as a specimen plant, grouped for foundation plantings or installed in large numbers as hedges. Some authorities include height as a criterion for the shrub rose classification, asserting that true shrub roses should reach 4 feet or more in height at maturity. Some modern rose breeders, notably William Radler, breeder of the Knockout series of roses, have created shrub roses that are somewhat smaller (2 to 4 feet tall).
There are many species and varieties of shrub roses. Big, rangy bushes, like the hybrid musk "Penelope," which can grow up to 8 feet tall, fall into the category. The smaller "Fair Bianca," at only 3 to 5 feet tall, also ranks as a shrub rose and could be used as a low hedge. Flowers can be simple, like those of the five-petaled "Golden Wings," or sumptuous, like the shell pink "Souvenir de la Malmaison."
Old Shrub Roses
Old roses are usually defined as those introduced into commerce before 1867, when the first hybrid tea rose was introduced. Most old roses can be defined as shrub roses. Some well-known examples include the classic, white alba rose "Madame Hardy," which grows from 4 to 7 feet tall; the fragrant, pink "Old Blush," that grows 3 to 10 feet high; hybrid perpetual "Reine des Violettes," with many-petaled violet flowers; and "Felicia," a hybrid musk with pink flowers and a pronounced old-rose fragrance. The species rose, Rosa glauca, with its blue-tinged foliage and red stems, is also an excellent shrub rose.
Modern Shrub Roses
Over the last two decades interest in shrub roses has increased, with many breeders working on versatile shrubby varieties. Even before that, Dr. Griffith Buck, of Iowa State University, developed a series of hardy, disease-resistant varieties, the most famous of which is the pink-flowered "Carefree Beauty." Many of the roses developed by English breeder David Austin fit into the shrubby category. The best known Austin rose is the peachy-pink "Abraham Darby." Available in several colors, German-bred "Pavement" series roses have also gained popularity.
Shrub roses generally require less care and attention than upright bedding types like hybrid tea and floribunda roses. When used as hedges, they provide three seasons of interest, with flowers from mid-sping through frost on reblooming varieties, and colorful hips in the late fall and early winter. The presence of hips, which are attractive to birds, also make shrub roses desirable as habitat plants. Some types of shrub roses, like the salt spray-tolerant rugosas, are also useful for special situations like seaside plantings. Mass plantings can also be useful for erosion control.
Planted en masse or in smaller groups, shrub roses have the same problem as their upright, bedding rose cousins--the susceptibility to insect and disease predation that is characteristic of any monoculture. Good air circulation between plants will help with fungal diseases like powdery mildew and black spot.