The genus Rosa encompasses one of the most diverse groups of flowering plants cultivated globally, featuring over 300 species and tens of thousands of cultivars. This wide variation in form, color, and growth habit requires a systematic method of organization. Rose classification is generally determined by two main factors: the plant’s ancestry and the year it was introduced into cultivation. The American Rose Society divides these plants into three broad categories—Species, Old Garden, and Modern Roses—which helps to distinguish between the original wild types and the highly bred varieties of today.
The Ancestral Foundation: Species and Wild Roses
Species roses, or wild roses, are the original forms that developed naturally without human intervention, forming the genetic foundation for all cultivated varieties. Their flowers are typically simple, consisting of only five petals arranged flatly around a central cluster of stamens, a characteristic of the Rosaceae family.
These ancestral plants generally bloom only once per season, producing a single flush of flowers in late spring or early summer. Species roses are noted for their robust nature, exhibiting superior disease resistance and hardiness compared to their hybridized descendants. Following their bloom period, many wild roses develop prominent, often colorful, fruits called rose hips, which contain the seeds and are rich in vitamin C.
Historical Charm: Old Garden Roses
Old Garden Roses (OGRs) are defined as any rose variety that existed prior to 1867. These varieties often possess a deep, complex fragrance and a diverse range of flower forms, including quartered, cupped, or globular shapes. Many OGRs display superior cold tolerance and disease resistance, traits inherited from their wild ancestors.
A significant portion of OGRs are once-blooming, providing a concentrated display of flowers annually. Prominent classes within this group include:
- Albas, known for their extreme hardiness and pale flowers.
- Damasks, prized for their intensely aromatic blooms.
- Centifolias, sometimes called Cabbage Roses due to their numerous petals.
- Moss Roses, characterized by a resinous, moss-like growth on their sepals.
Modern Hybrids: The Dominant Varieties
Modern Roses include all varieties bred and introduced after the 1867 benchmark. Breeding efforts focused primarily on recurrent blooming and specific flower architecture. This category dominates contemporary horticulture, as the vast majority of garden roses grown today fall into this modern classification and flower repeatedly throughout the growing season.
The most recognizable modern type is the Hybrid Tea, which typically produces large, high-centered, single flowers on long, upright stems. This characteristic makes them the standard for cut flowers, though they are often less cold-hardy than older varieties. They typically bloom in cycles, with three distinct flushes occurring between summer and late autumn.
The second dominant modern class is the Floribunda, a name derived from the Latin for “many-flowering”. Floribundas are distinguished by their habit of bearing multiple blooms in large clusters or trusses on a single stem, creating a massive color display. These roses generally grow into a bushier, more compact shrub than Hybrid Teas, and they tend to be hardier and more disease-resistant.
A third type, the Grandiflora, was created by crossing Hybrid Teas and Floribundas, aiming for the long stems and high-centered blooms of the Hybrid Tea alongside the clustered flowering of the Floribunda. Additionally, Polyantha roses, which are smaller, sturdy plants that produce dense clusters of tiny flowers, are considered ancestors to the Floribunda and are often used for mass planting and edging.
Functional Classifications: Climbers, Shrubs, and Miniatures
Beyond ancestry, roses are also grouped by their physical structure and landscape use, known as functional classification. These types may belong to either the Old Garden or Modern categories but are defined by their growth habit.
Climbing roses are characterized by long, stiff, arching canes that require physical support, such as a trellis or arbor, to grow vertically. Unlike true vines, they do not twine on their own and must be trained and tied to a structure. These types include both modern large-flowered climbers and older varieties that possess this vigorous growth habit.
Shrub roses are generally rugged, vigorous plants that often grow larger than typical bedding roses. This group includes many hybrid lines, such as the popular David Austin English Roses, which were bred to combine the recurrent blooming of modern types with the full, fragrant flower forms of Old Garden Roses.
Miniature roses are true roses defined by their diminutive size, with plants typically ranging from six to thirty inches in height. Both the leaves and the flowers are proportionally smaller, often mirroring the high-centered form of a Hybrid Tea in miniature. Groundcover roses are another distinct functional type, characterized by a low, spreading, and often sprawling habit that makes them suitable for covering banks or mass planting.