Silphium perfoliatum - Silphe perfolié

Silphium perfoliatum, the cup plant, is a giant perennial whose sturdy stems bear numerous bright yellow daisy-like flowers in high summer. Its ample foliage has a remarkable feature: the leaves join around the stems, forming small cups capable of holding rainwater. Very hardy, long-lived and visited by pollinating insects, this plant is at home in a naturalistic meadow, on a bank, or in a spot in the garden where its rootstock can spread at will.

The cup plant belongs to the Asteraceae family, like sunflowers, rudbeckias and asters. It is a herbaceous deciduous perennial: its stems die back in autumn, and new shoots emerge from the rootstock in spring. This wild plant is native to south-eastern Canada and much of the central and eastern United States. It grows in damp meadows, meadows near rivers, ditches, cool woodland edges and around lakes. Its rootstock develops deep roots as well as superficial rootstocks that spread gradually. A mature plant reaches 2 to 2.50 m in height with a spread of 80 cm to 1 m, but several plants can eventually form a much larger colony. The thick, upright stems have four well-marked angles. They are sparingly branched in their lower part, then divide at the top to bear the flowers. The medium green leaves are arranged in pairs. Oval to broadly lanceolate, coarsely toothed and rough to the touch, they measure 15 to 25 cm in length. The base of each pair of leaves completely surrounds the stem: the lamina appears to be pierced by it, which explains the qualifier perfoliatum. The small cavity they form collects dew and rainwater; birds come to drink there, while ripened seeds are sought after by goldfinches. Flowering extends from July to September; the terminal branches bear golden-yellow heads 7 to 9 cm in diameter. They are composed of numerous ligulate florets, resembling petals, arranged around a yellow heart. Bees, bumblebees, butterflies and hoverflies visit them for their pollen and nectar. The plant tolerates temperatures below –25 °C. The stems, heavy when in flower, can be laid flat by strong wind or a storm. The cup plant self-seeds readily on bare ground; young plants should be removed early, as their root system quickly becomes difficult to extract.

It is the perfect type of plant to accompany large grasses such as Miscanthus and Panicum in an open, sunny garden. This cup plant can also be paired with other tall plants for moist ground such as Vernonia crinita 'Mammuth' and Persicaria polymorpha, a robust knotweed bearing large white inflorescences in summer. Its cut stems can be used in large country-style cut flower arrangements, with large daisies for example. Cut them when the first flowers are open, then remove the lower leaves, which are too bulky and rough.