If you were fortunate enough to take a tropical vacation this winter it’s likely you saw blooming Chinese hibiscus (Hibiscus rosa-sinensis), perhaps planted around the patio where you were sipping mai tais. You won’t find this tender species growing at the Arboretum (it can be damaged by temperatures in the 40s and killed outright at 32 F), but we do have accessions of two other Hibiscus species that put on a fine floral show.
Rose of Sharon (Hibiscus syriacus [pdf]) is a densely branched large shrub or small tree with a broad native range from Korea to India. (Our accessions — 341-53*A and its propagules 1142-81*A, B, and D — are from South Korea, where rose of Sharon is the national flower.) It has a long bloom season from midsummer to early fall, producing many showy, cupped, five-petaled flowers (cultivars with semi-double or double flowers also exist). Flower colors range from white to pink, rose, lavender, purple, and “almost blue,” sometimes with a contrasting eye. While rose of Sharon provides late summer color as well as nectar for bees and hummingbirds, it often reseeds prolifically and has become invasive in some regions, especially the Mid-Atlantic and southeastern U.S. If in doubt, select a seedless cultivar, or a different plant entirely.
The Arboretum’s other Hibiscus species is H. moscheutos ssp. palustris, known as marsh mallow or sea hollyhock. Taxonomic sources disagree on nomenclature, variously listing it as a separate species (H. palustris), a subspecies, as we list it here, or simply lumped in under the name H. moscheutos. This herbaceous perennial (sometimes with woody stem bases) grows in marshes and other moist-soil areas in southern Ontario and much of the eastern U.S. The Arboretum’s accessions are from Ontario and Nantucket Island, MA, and all are planted along the banks of Dawson Pond. Its upright stems and large green leaves are unremarkable, but in late summer its large, candy pink flowers delight Arboretum visitors and provide food for bees. Marsh mallow makes a fine addition to gardens as long as the soil is kept moist.
–Nancy Rose, editor of Arnoldia