Sun/shade: Full sun
Soil moisture: Medium
Flowering period: June to September
Host plant for 6 caterpillar species
Whorled rosinweed’s open, branching upper stems begin to bloom in mid-summer, and wherever the plant thrives, an airy layer of sunny flowerheads soon softens the transition from meadow to sky. Similar to several other silphium species, but generally unlike the sunflowers, the flowering portion of whorled rosinweed’s stems is nearly bare of leaves. The pleasing visual effect produced is that of yellow flowerheads hanging in the air, with only an inconspicuous network of stems indicating a connection to underlying vegetation. 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 partial shade in addition to full sun, and its native NE Ohio habitats include woodland openings as well as meadows. The plant grows well in soil moisture ranging from moderately wet to moderately dry, forming small colonies through the production of short underground stems called rhizomes. Attaining a mature height of 5 – 8’, whorled rosinweed is a tall, long-lived perennial that reliably blooms from mid to late summer year after year.
Photo by Andrew Cannizzaro.