Coptis trifolia
threeleaf goldthread
Overview
Coptis trifolia is a low evergreen perennial of cool northern forests and bogs, reaching only 2-6 inches (5-15 cm) tall. Its name comes from the slender, bright-yellow rhizome that threads through the soil surface and gives rise to glossy basal leaves. Each leaf divides into three fan-shaped, toothed leaflets that stay green through winter, sometimes bronzing in exposed sites. In late spring a single leafless stalk bears one star-shaped flower whose white, petal-like sepals spread to about 0.5 inch (12 mm); the true petals are reduced to small yellow club-shaped structures. The flower gives way to a cluster of beaked follicles held above the foliage. C. trifolia spreads by its creeping rhizomes into low evergreen mats in sphagnum bogs, coniferous swamps, and mossy woodland floors. It needs cool, consistently moist, acidic soil and declines where summers are hot or soils dry out. Growth is slow, and the plant takes several years to form a sizable patch. Its low stature means it is readily overtopped by taller groundcovers. It is hardy in USDA zones 2 through 7.
Native Range
Native to northern North America, from Greenland and Labrador west to Alaska and south into the northern United States and the Appalachian mountains. It grows in sphagnum bogs, coniferous swamps, and damp mossy woods on acidic soils.Suggested Uses
Planted in bog gardens, shaded acidic borders, and woodland groundcover plantings in cool climates. It suits the front edge of a moist, shaded bed alongside mosses and small ferns.How to Identify
Appearance
Size & Dimensions
Height2" - 6"
Width/Spread6" - 1'
Reaches mature size in approximately 4 years
Bloom Information
The solitary white flowers open in late spring, generally May through June, lasting one to two weeks. What appears as white petals are actually sepals; the petals themselves are reduced to small yellow nectar cups. Beaked seed follicles follow and persist into summer.
Detailed Descriptions
Foliage Description
Glossy dark greenGrowing Conditions
Sun Requirements
Requires 2-4 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
Care & Maintenance
Care Guide
Grow C. trifolia in part to full shade with cool, acidic, humus-rich soil kept evenly moist. It performs in the conditions of a bog or woodland garden and fails in hot, dry, or alkaline sites. A mulch of sphagnum or conifer needles helps hold moisture and acidity around the shallow rhizomes. The plant tolerates winter cold to USDA zone 2 but is sensitive to summer heat. Propagation is by division of the rhizome in spring or by seed, both of which establish slowly. Once settled in suitable ground, it needs little attention.Pruning
No pruning is required. Remove any leaves damaged by winter exposure in early spring to tidy the evergreen mat. Otherwise the foliage is left in place year-round.Container Growing
✓ Suitable for container growing
Minimum container size: 1 gallons