Hypericum ascyron aka Great St. Johnswort

Hypericum ascyron is a perennial in the St. John's wort family. Gardeners call it great or giant St. John's wort. Its native range spans temperate Asia and parts of North America. These include eastern Canada and the central and eastern United States. It grows in meadows, beside streams, and on moist wooded slopes. In northern Japan, it also grows in mountain grasslands. It is not native to Britain or Ireland.

Plants form upright clumps rather than woody shrubs. Garden plants reach 2–5 feet (0.61–1.52 metres) tall. They spread 1–3 feet (0.30–0.91 metres) wide. The straight stems carry oval leaves with no leaf stalks. Leaves measure about 0.17–0.33 feet (0.05–0.10 metres) long. Their width reaches about 0.08 feet (0.025 metres). The tall stems give the plant a clear upright shape. They also suit both fresh and dried flower arrangements.

Yellow flowers form rounded or pyramid-shaped clusters near the stem tops. Each bloom measures about 0.17 feet (0.05 metres) across. Five petals surround a dense tuft of yellow stamens. Each flower also has five styles. Missouri Botanical Garden gives July to August as the bloom season. Chicago Botanic Garden also lists May to June flowering. Bumblebees and other insects visit the flowers, which also attract butterflies. The bright blooms make this a useful plant for borders.

Grow it in moist soil that drains well. It accepts full sun or some shade. It can grow in clay and shallow, rocky ground. Sources describe its water needs as medium to wet. Missouri Botanical Garden lists USDA zones 3–6; Chicago extends this to zone 7. Care needs are low, and serious pest or disease problems are not reported. Deer and rabbits tend to leave it alone. Use it as a single specimen or let groups spread naturally. Woodland edges and rain gardens also suit it. It may seed itself where conditions suit it. Propagation methods include seed, cuttings, and spring division. Seeds need cold, moist treatment and light to germinate.

Plants For A Future records cooked young leaves, shoot tips, and flower buds as edible. It also lists leaves as a tea substitute. The same source records traditional medicinal uses for several plant parts. These include fruit, roots, and the whole plant. Such records do not establish safe or effective treatments. It reports no known hazards, but this does not prove safety for people or pets.