Last fall our staff planted a specimen of Rosa rugosa L. (family Rosaceae) outside the wrought-iron fence along Hilgard Avenue. This species is a personal favorite, because R. rugosa has one of the strongest fragrances in the rose genus and reminds me of coastal New England, as on Cape Cod, where it commonly flourishes behind the fore dunes. It grows vigorously in zones that receive salt spray, where it forms dense thickets of canes armed with masses of sharp-pointed stem prickles as well as scattered prickles along the lower leaf axis (the rachis).
I learned years ago from Harvard professor Dick Howard that this rose--which I used to call simply the beach rose--was a native of eastern Asia, brought to Europe in time to be named by Linnaeus and then introduced to New England around 1845. Along Massachusetts beach fronts, the plant escaped, likely by dispersal of its orange-red hips (fruits), and is now naturalized (meaning that is appears like a native). The species is known generally as Japanese rose, hedgehog rose, Ramanas rose, or, oddly, sea tomato (referring, of course, to the color of the fruit). The hip is edible, though very seedy, and can be used to make preserves.
Rosa rugosa is distinctive because its pinnately compound leaf has seven or nine semi-glossy leaflets that appear wrinkled (rugose). Each major and minor vein of the leaflet is sharply defined, sunken on top and raised underneath. The elliptical leaflet is serrulate (it has shallow serrations) and appears to be thick. The thickness, however, is somewhat an illusion due to the raised veins on the underside, although leaflets are tougher and thicker on plants growing along the beaches, because ocean salts cause leaves to develop much thicker, watery tissues. As with most roses, there is a pair of leaf-like wings (stipules) attached to the base of the rachis.
The flower of R. rugosa is like a single rose, about seven to nine centimeters across, with five pointed, green sepals (each with a leaf-like tip), five separate broad petals, about one hundred stamens in the center, and an inferior ovary that forms into the fleshy fruit. Flowers on our specimen are rose-pink (which would be called form rosea in the trade), but there are also a dark rose (rubra) and pure white (alba) forms. All flower colors can be observed within a single population in Massachusetts, suggesting a fairly simple genetic basis for the various forms. Cultivars with double flowers are also available in the trade. Regardless of the color, the daytime fragrance of Rosa rugosa is strong and unforgettable.