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Hypericum swinkianum (Swink's st. johnswort)
Smith, R.W.

Hypericum swinkianum

Hypericum swinkianum Wilhelm & Rericha

Swink's St. Johnswort

Clusiaceae (Mangosteen Family)



USDA Native Status: L48 (N)

Much-branched shrub to 1.8 m high, with exfoliating bark; leaves coriaceous, narrowly to broadly oblong, broadest at or near the middle, weakly revolute or thickened at the margins, the larger ones 12 cm wide, 3.55 cm long, usually with axillary fascicles; adaxial leaf surfaces green, the abaxial surfaces pale; flowers 33.5 cm in diameter, 731 in terminal dichasia; sepals rotund-ovate, 912 mm long; petals yellow, about 1.5 cm long, persistent, broadly ovate to subrotund, much longer than the sepals; stamens numerous, the androecium 1.61.9 cm across; styles 5; capsules 5-parted. (Reslit: 3179).


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Plant Characteristics

Duration: Perennial
Habit: Shrub
Leaf Shape: Oblong
Leaf Texture: Leathery
Inflorescence: Dichasium
Fruit Type: Capsule
Size Notes: To about 6 feet in height. (Reslit: 3179).
Fruit: "Capsules 5-parted." (Reslit: 3179).

Bloom Information

Bloom Color: Yellow
Bloom Time: Jul , Aug


Native Habitat: Hypericum swinkianum typically occurs in acid wetlands and sand prairies. In Illinois and Indiana it is found in wet to mesic acid sand prairies, margins of sphagnum bogs, and swales in black oak savannas and sand flatwoods. These habitats in the Chicago region are restricted to older lake plain of the Glenwood and Calumet stages of glacial Lake Chicago and in the Kankakee Sands section. In Michigan, it occurs in a Spartina-dominated swale in a Pinus banksianaQuercus ellipsoidalis savanna on an extensive sandy outwash plain in Cheboygan County. (Reslit: 3179).

Growing Conditions

Water Use: Medium , High
Soil Moisture: Moist , Wet
Soil pH: Acidic (pH<6.8)
Cold Tolerant: yes

Web Reference

Webref 23 - Southwest Environmental Information Network (2009) SEINet - Arizona Chapter

Additional resources

USDA: Find Hypericum swinkianum in USDA Plants
FNA: Find Hypericum swinkianum in the Flora of North America (if available)
Google: Search Google for Hypericum swinkianum


Record Modified: 2023-01-10
Research By: Joseph A. Marcus

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