Silphium perfoliatum (Cup plant)

Silphium perfoliatum L.

Cup plant, Indian cup, ragged cup, carpenter weed

Kingdom	Plantae	Plants, but not fungi, lichens, or algae
Subkingdom	Tracheobionta	Vascular plants—plants with a “circulatory system” for delivering water and nutrients
Division	Magnoliophyta	Flowering plants, also known as angiosperms
Class	Magnoliopsida	Dicotyledons—plants with two initial seed leaves
Subclass	Asteridae	A large class that encompasses asters
Order	Asterales	Flowering plants with a central disk flower and surrounding petals, like daisies
Family	Asteraceae	The aster family, which also includes daisies and sunflowers; from the Greek ἀστήρ, “star,” for the star-shaped flowers
Genus	Silphium
Species	perfoliatum	Refers to the stem which “perforates” the leaf

About plant names...

Cup plant, named for the cup-shaped depression formed where opposing leaves meet the stem, is another member of the very large aster family. It is a North American native.

Identification: Plants are 4-10' (1.2-3 m) tall, on single stalks that branch only near the flowering top. They could be mistaken for a type of sunflower, except for the unusual leaves. The stem is thick and hairless, four-sided, and green or purple. Leaves are opposite, joined to each other at the stems, producing a depression between them that holds water. The trapped water often attracts birds. Leaves are rough to the touch, and coarsely toothed. Flowers have a dark yellow central disk surrounded by 18-40 bright yellow petals (“ray florets”). They appear from July to October. Fruits are egg-shaped achenes ¼-½" (7.6-12 mm) long, with wings.

From Britton, Nathaniel Lord, and Brown, Addison, An illustrated flora of the northern United States, Canada and the British Possessions, 1913; scanned by the Natural Resources Conservation Service.