Midewin National Tallgrass Prairie
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  • Round-fruited St. John's Wort

    SCIENTIFIC NAME: Hypericum sphaerocarpum

    COMMON NAMES: Round-fruited St. John's Wort, Roundseed St. Johnswort

    BLOOM TIME: June, July, Aug, Sept


    • Grows up to 2 ½ ft. tall with branch clusters at top.
    • Pretty yellow flowers grow at cluster ends & each have 5 1/2 in. petals & multiple stamens.
    • Flowers have mild buttercup fragrance.
    • Habitat: woods, roadsides, & fields.
    • A true prairie plant scattered throughout Illinois.
    • Old lore states it got its name from the red resin in back glands of flower petals.
    • In Middle Ages it was said, the red drops were blood shed by St. John the Baptist when he was beheaded.
    • The word ”wort” is an old English word for plant.


    • Bumblebees & other long-tongued bees are probably the most important pollinators of the flowers. 
    • Insects collect or feed on the abundant pollen, because the flowers offer no nectar.
    • The caterpillars of the Gray Hairstreak butterfly reportedly eat the seed capsules, although it is not a preferred host plant.
    • Like other St. John's Worts, the foliage of this species contains a toxic chemical that causes photosensitive skin reactions, particularly in light-skinned animals, and can irritate the gastrointestinal tract.
    • Mammalian herbivores usually leave this plant alone if other food sources are available.