Woodland Perennial
Hylomecon, Genus, japonica, Species,
- Genus & species
Japanese wood poppy
Japan, Korea, northeastern China, Russian Far East
Overview
Hylomecon japonica is a rhizomatous, clump-forming perennial that grows 8–16 inches (20–40 cm) tall and 12–18 inches (30–45 cm) wide, spreading slowly by underground rhizomes. Leaves are pinnately compound with 3–5 ovate to lance-shaped leaflets 2–4 inches (5–10 cm) long, toothed along the margins, bright green above and paler beneath. Flowers are yellow, four-petaled, 1.5–2 inches (4–5 cm) across, borne singly or in clusters of 2–3 on stems rising above the foliage in spring. Cut stems exude yellow-orange sap, as in other members of the poppy family. Fruits are narrow capsules 1–2 inches (2.5–5 cm) long that split to release seeds. Plants die back to the rhizome during summer drought and in autumn. The species is hardy in USDA zones 4–8 and is the only species in the genus Hylomecon. Growth is slow, and colonies expand 3–6 inches (8–15 cm) per year.
Native Range
Hylomecon japonica is native to Japan, Korea, northeastern China, and the Russian Far East, where it grows in moist deciduous woodland and along shaded stream banks.Suggested Uses
Hylomecon japonica is used as a spring groundcover and woodland garden perennial under deciduous trees and shrubs, with spacing of 12–18 inches (30–45 cm) between plants. It is also planted along shaded stream banks and in shade borders.How to Identify
Appearance
Size & Dimensions
Height8" - 1'4"
Width/Spread1' - 1'6"
Bloom Information
Hylomecon japonica blooms in spring, typically April to May, with individual flowers lasting 3–5 days and plants flowering for 3–4 weeks. Flowers are visited by bees and hover flies. Foliage persists until summer dryness or autumn.
Detailed Descriptions
Foliage Description
Bright green above, paler beneathGrowing 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
Hylomecon japonica grows in part shade to full shade, with 2–4 hours of direct light, in humus-rich, consistently moist, well-drained soil of pH 5.5–7.0. Plants need 1 inch (2.5 cm) of water weekly during dry periods, and foliage goes dormant early in dry summers. Hardiness is USDA zones 4–8. A 2-inch (5 cm) leaf mulch layer limits root drying and adds organic matter. Slugs feed on young shoots in spring. Plants self-sow lightly, and division of rhizomes takes place in early fall.Pruning
No structural pruning is needed. Dormant foliage is cut to the ground in late fall or summer when it browns. Spent flower stems are removed to limit self-seeding, and rhizome clumps are divided every 3–4 years in early fall or early spring.Pruning Schedule
Prune: October–November
fall
