Cup Plant Silphium perfoliatum

Each summer a line of cup plants grows up along my road. There was only one cup plant the first year. The lines have gained in length and number of plants every year since. New lines of plants have started nearby.

The thick stem and massive leaves make the cup plant noticeable. Then there is the size: eight feet tall! The flowers seem so small for such an impressive plant.

The plants seem to grow slowly. Perhaps this is because they get so tall. Even the short ones are taller than I am.

The stems are stiff and difficult to pull over without breaking them. I resorted to pulling my truck over close to the ditch and climbing into the pickup bed to get pictures of the flowers.

 

Silphium perfoliatum L.

July to September                                       N                                 Family: Asteraceae

                                                                                                            Tribe: Heliantheae

cup plant flower

Flower: A spray of flower stalks comes up out of the top pair of leaves. These stalks can branch. Each is tipped with a flower head of a disk of yellow tube flowers and 18 to 35 orange yellow ray flowers. The cup behind the flower is green formed by numerous bracts with pointed tips but appearing almost fused around the base of the flower head, smooth and hairless.

cup plant side flower

Leaf: The opposite leaves are large, over a foot long and nearly a foot wide at the base end slowly tapering to a point. The two leaves join together to surround the stem and attach at a swollen node forming a depression around the stem. The edges have widely separated teeth. The strong midvein holds the leaves out stiffly although the  last quarter droops down. The leaves are green on the tops and pale green underneath.

cup plant leaf

Stem: A single, unbranched stem can reach ten feet. The stem is square, ridged, with a few scattered short hairs, coarse to the touch and stiff.

cup plant under leaf

Root: The perennial roots are rhizomes forming colonies.

cup plant stem

Fruit:

Habitat: This plant prefers moist areas such as roadside ditches, moist woods and stream banks. It likes partial sun and light shade.

Cup Plant

Cup Rosinweed

cup plant

Few plants are as impressive as the Cup Plant. The inch thick stem and massive leaves rise up out of the surrounding plants then tower over them. Most Cup Plants seem to top out at seven feet. Some are shorter and a few are up to three feet taller.

Cup Plant leaves are massive. Each pair points in the opposite direction from the previous pair. The depression where the fused leaves join the stem can hold rain water.

For such a large plant, the flower heads are small, only three inches across. Larger plants can have a bouquet of them sprouting up out of the top leaves with six open at a time.

Because of the square stem and leaves at regular intervals, an old name for the plant was measuring weed. Its accuracy for measuring is questionable.

The rhizome root is perennial and puts up more than one stem in a line. The older the root, the more stems it puts up.