Hypericum L.
Family: Hypericaceae
St. John's-Wort
Hypericum image
Robert W. Freckmann  

Key to Wisconsin Hypericum

Author: John G. Zaborsky

    • 1a. Petals pink to purple, rarely open, imbricate in bud; stamens 9, held in 3 distinct fascicles of 3 stamens each, these alternating with hypogynous glands 2

    • 1b.Petals yellow, usually open, convolute in bud; stamens few to numerous, not in distinct fascicles (although sometimes the filaments slightly connate at the base), hypogynous glands absent 3

    • 2a.Sepals 2.8–4.8 mm long, the apices obtuse to rounded; styles 0.6–1.5 mm long H. fraseri

    • 2b.Sepals 4.3–8 mm long, the apices acute; styles 1.7–3.6 mm long H. virginicum

    • 3b.Leaves not reduced, linear to elliptic to lanceolate 4

    • 4a.Shrubs; styles coherent at anthesis, splitting in fruit; stamens over 100 5

    • 4b.Herbs (the bases sometimes slightly woody); styles distinct at anthesis (except in H. ellipticum and H. sphaerocarpum); stamens fewer than 100 (except in H. ascyron) 6

    • 5a.Carpels 3; inflorescences axillary and terminal H. prolificum

    • 5b.Carpels 5; inflorescence strictly terminal H. kalmianum

    • 6a.Carpels 5; flowers 4–6.5 cm wide; stamens numerous H. ascyron

    • 6b.Carpels 3; flowers less than 3 cm wide; stamens fewer than 100 7

    • 7a.Petals (and often sepals and/or leaves) with distinct black spots or streaks 8

    • 7b.Black spots absent 9

    • 8a.Styles longer than the ovary; black spots largely restricted to margins or apices of petals, rare or absent elsewhere; stems angled; leaves with a decurrent midrib; tertiary leaf veins not densely reticulate H. perforatum

    • 8b.Styles shorter than the ovary; black spots scattered across entire surface of petals (and sometimes sepals and lower leaf surfaces); stems terete; leaves not decurrent; tertiary leaf veins densely reticulate H. punctatum

    • 9a.Leaves definitely pinnately-veined; stamens more than 20; petals 4.6–8.6 mm long; styles coherent 10

    • 9b.Leaves with 3–5 (or only 1) strong longitudinal veins, lateral veins obscure or absent; stamens fewer than 20; petals less than 6.5 mm long; styles separate 11

    • 10a.Plants 30–60 cm tall, not rhizomatous; leaves linear-elliptic, 30–58 mm long; seeds 2–2.7 mm long H. sphaerocarpum

    • 10b.Plants 15–35 cm tall, rhizomatous; leaves elliptic to ovate, 16–33 mm long; seeds 0.5–0.8 mm long H. ellipticum