Pronounced (approximate): hy-PAIR-ih-kum AS-kih-ron
Large yellow flowers have five often twisted petals. Numerous long stamens surround the central ovary.
Giant St. John's-wort (Hypericum ascyron): flower details. Tap the photo to open the gallery.
Family Hypericaceae
Life cycle Perennial
Blooms July–August
Height 2 to 5 feet
Habitat sun; moist; along shores, wet meadows, thickets
Common names: Giant St. John's-wort · Great St. John’s-wort
Bloom timing varies with latitude, weather and local conditions.
Explore reported observations. Sightings are not a complete range map.
sun; moist; along shores, wet meadows, thickets. Flowering season: July–August.
The large flowers and broad stem-clasping leaves distinguish this tall perennial from the smaller-flowered, woody St. John’s-worts.
Large yellow flowers have five often twisted petals.
Numerous long stamens surround the central ovary.
Opposite entire leaves clasp the upright stem. Pair close views with a photograph of the whole plant.
12 field photographs. Select a photograph to enlarge it; use Load more photos to see the rest.
Native in North America.
Reported U.S. distribution
CT, IA, IL, IN, KS, MA, ME, MI, MN, MO, NH, NY, OH, PA, VT, WI
Includes native and introduced state records where listed; a state record does not imply occurrence in every county.
Observation maps show submitted records, not every place the plant occurs. Follow local access rules when visiting a site.
Practice recognizing Giant St. John's-wort in the flower quiz, or compare it with other plants in the guide.
Field photographs: Where’s Wildlife.