Before we go much further in our Landscaping with Roses series, we need to touch on modern rose classifications.
The International Registration Authority for Roses (IRAR) has remained with the American Rose Society, so designated by the International Society for Horticulture Science since 1955. As such, the IRAR has divided roses into four general classifications as shown in the table below.
| Horticultural Classification | Rose |
| Old Garden Roses | Alba |
| Ayrshire | |
| Bourbon | |
| Boursault | |
| Centifolia | |
| China | |
| Cl. Bourbon | |
| Cl. China | |
| Cl. Hybrid Perpetual | |
| Cl. Moss | |
| Cl. Tea | |
| Damask | |
| Eglanteria | |
| Gallica | |
| Hybrid Alba | |
| Hybrid Bracteata | |
| Hybrid Bourbon | |
| Hybrid Canina | |
| Hybrid China | |
| Hybrid Foetida | |
| Hybrid Multiflora | |
| Hybrid Perpetual | |
| Hybrid Sempervirens | |
| Hybrid Setigera | |
| Hybrid Spinosissima | |
| Moss | |
| Miscellaneous OGR | |
| Noisette | |
| Portland | |
| Species | |
| Tea | |
| Shrubs | Hybrid Blanda |
| Hybrid Hugonis | |
| Hybrid Laevigata | |
| Hybrid Macounii | |
| Hybrid Moyesii | |
| Hybrid Musk | |
| Hybrid Nitida | |
| Hybrid Nutkana | |
| Hybrid Rugosa | |
| Hybrid Suffulta | |
| Kordesii | |
| Shrub | |
| Hybrid Teas, Grandifloras, Floribundas, Polyanthas, Ramblers & Climbers | Cl. Floribunda |
| Cl. Grandiflora | |
| Cl. Hybrid Tea | |
| Cl. Polyantha | |
| Floribunda | |
| Grandiflora | |
| Hybrid Tea | |
| Large-Flowered Climber | |
| Polyantha | |
| Rambler | |
| Miniatures | Cl. Miniature |
| Miniature |
Rosarians frequently debate into which classification a rose should belong. Polyanthas, for example, exhibit an old floral form and were introduced in 1875. Some contend they should belong in the Old Garden Roses classification in the table above. Others contend they are a "modern" rose, and therefore belong in their current classification. Likewise, Hybrid Musks were introduced in the 1920's and 30's; however, most display a distinctly "antique" floral form.
