Description
Silphium – Prairie Dock – Rosinweed –
There are 20 tall herbaceous perennials in the Asteraceae family, in this genus. They are found naturally occurring in fields, prairies and open woodlands and scrub in Canada and Central and Eastern USA. Their, erect, sparsely branched stems exude resinous sap with a strong turpentine like scent. The opposite or alternate, leaves, sometimes all basal, are lance shaped or pinnatifid. Sunflower like yellow flowers, rarely white, are borne in branching corymbs. Excellent for naturalizing in a wild garden or woodland garden, or for the back of a herbaceous border.
Grow in moderately fertile, moist, deep, neutral to slightly alkaline soil in full sun or partial shade, best in heavy soil. Divide in spring.
Prone to downy mildew, rust, and Cercospora leaf spot.
S. perfoliatum – Cup Plant – This erect, hairless or nearly hairless, clump forming perennial found form Ontario, Canada to Oklahoma and Georgia, USA grows 8′ feet tall and 3′ feet wide. It produces opposite, triangular-ovate, coarsely toothed, bristly leaves, to 14″ long, with winged stalks. The upper leaves are perfoliate. From mid summer to early autumn, bears terminal, open branched, corymb like inflorescences of yellow flowers, to 3″ across, with darker centers.
Zones 5-9
