Silphium asteriscus (Whorled Rosinweed) Seed Packet

Silphium asteriscus var. trifoliatum, or the whorled rosinweed, is a delightfully whimsical upright summer flowering perennial that adds height and brightness to the landscape and wild plantings. Native to prairies and meadows, as well as open, dappled woodlands, rocky outcrops, savannas, or shaded forest edges, whorled rosinweed is highly versatile.

Staying low as a clump of rough-textured and dense basal rosette, whorled rosinweed shoots up purple-stemmed stalks with whorled leaves in May and June, reaching 3-6 feet in height, and creates clusters of lemony or golden yellow sunflower-like blooms that can continue sporadically into fall. The large, flat seeds are enjoyed by birds such as goldfinches, which pinch the seeds out of the flowerheads.

Consider using this species instead of Silphium perfoliatum, the cup-plant, which isn't native to central and eastern Virginia, and has a reputation for aggressive spreading through rhizomes. Silphium asteriscus stays a few feet smaller than cup-plant, is longer blooming, and is clumping in habit rather than rhizomatous. Whorled rosinweed can happily colonize an area through light reseeding (assuming birds leave any seed behind), and makes an excellent addition to wild meadows or plantings that need a strongly upright plant.

Silphiums are tough as nails, with roots that descend deep into the soil, sometimes many yards down. They need well draining soil, and are highly tolerant of drought once established. Rosinweed can grow in poor, rocky soils, and along steep inclines.

There are two varieties, var. asteriscus (Starry rosinweed) and var. trifoliatum (Whorled rosinweed), the latter being the more commonly occurring species to the central Virginia region.