Hypericum tetrapterum
square stemmed saint John's wort
Europe, North Africa, and western Asia
Overview
Hypericum tetrapterum is an upright perennial of wet ground, named for its square stems, which carry four narrow raised wings along their length. It grows 12-28 inches (30-70 cm) tall from a creeping base, the stems branching toward the top. The paired, stalkless leaves are oval, 0.4-1.2 inches (1-3 cm) long, clasp the stem, and are dotted with many small translucent glands that show as pinpricks of light when a leaf is held up. From June to September the branch tips carry open clusters of pale yellow flowers about 0.4 inches (8-12 mm) across, each with five petals and numerous stamens; the sepals and petal edges bear scattered black dots. It grows in marshes, wet meadows, fens, ditches, pond margins, and damp woodland rides on neutral to mildly acid soils that stay moist. Like its relatives it contains hypericin, which can cause photosensitive skin reactions in pale-skinned grazing animals that eat large amounts. It spreads slowly by short runners and by seed, forming small colonies. The pale flowers are smaller, about 8-12 mm, than the 15-25 mm flowers of perforate St John's wort (H. perforatum).
Native Range
Native to Europe, North Africa, and western Asia, from the British Isles and Scandinavia south to the Mediterranean and east to the Caucasus. It is naturalized in scattered parts of North America.Suggested Uses
Grown at pond and stream margins, in bog gardens, and in damp wildflower meadows for its summer-long pale yellow flowers and value to pollinators. It suits naturalistic and wildlife plantings on wet soil. It is not suited to dry borders, containers that dry out, or pasture grazed by pale-skinned livestock.How to Identify
Appearance
Size & Dimensions
Height1' - 2'4"
Width/Spread8" - 1'4"
Reaches mature size in approximately 2 years
Bloom Information
Detailed Descriptions
Foliage Description
greenGrowing Conditions
Sun Requirements
Requires 4-8 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight