Silphium trifoliatum

Whorled rosinweed’s open, branching upper stems begin to bloom in mid-summer, and soon after, an airy layer of sunny flowerheads can be seen softening the transition from meadow to sky. As with several other silphium species, the flowering portion of whorled rosinweed’s stems is nearly bare of leaves. This causes the upper stems to be quite inconspicuous, giving the pleasing impression that the yellow flowerheads are simply hanging in the air. The beguiling nature of the flowers is certainly not lost on the pollinator community, with native bees displaying a particular fondness for the blooms. The tubular central disk flowers are especially suited for long-tongued pollinators, with bumblebees and butterflies among the frequent visitors. Below the flowering stems, the plant’s leaves are arranged around its single tall stalk in groupings of three or four, offering an added element of visual interest.

One of the more easterly distributed members of the silphium genus, whorled rosinweed is tolerant of light shade in addition to full sun, and it occupies woodland openings as well as meadows. If planted at the edge of a tree canopy in the home landscape, however, the plant has a tendency to lean toward the sun. Whorled rosinweed grows well in soil moisture ranging from moderately wet to moderately dry, forming small colonies through the production of short underground stems. Attaining a mature height of 5 – 8’, this plant is a long-lived perennial that reliably blooms in midsummer year after year.

References: 1,2,3,4,5.

Photo by Julie Slater.