Kerria (Japanese kerria)

About Kerria (Japanese kerria)

Japanese kerria is a deciduous shrub from China, Korea and Japan with slender, bright green, cane-like stems and yellow flowers around Easter, single or in double pom-poms, plus a few more through summer (NC State, Morton Arboretum). It is one of the few shrubs that blooms well in shade, and its green stems add color in winter. It suckers and can form large colonies, and it has escaped from gardens into woods and forest edges in a few places in New England and North Carolina (Go Botany, NC Parks flora); USDA PLANTS gives it no noxious or invasive status, and we found no state invasive listing.

Hardy in zones 4-9 (NC State, Morton Arboretum). Stem tips can die back in harsh winters (Morton Arboretum). Not native to the U.S.

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

Plant container shrubs in spring or fall in part shade; in full sun the flowers fade (NC State, Morton Arboretum). Water deeply until established, which takes at least two growing seasons (UMN). Give it room or plan to pull suckers.

Soil

Well-drained, loamy soil rich in organic matter; it tolerates some alkaline soil and clay (Morton Arboretum), but NC State says to avoid heavy, poorly drained clay. Once established it handles some dryness.

Test the soil first and work in organic matter for a loose, well-drained loam; avoid heavy, soggy clay (NC State, Morton Arboretum, Clemson).

Feeding

• Spring after new growth starts, only if a soil test shows a need: slow-release complete fertilizer in a 3:1:2 ratio, or what the soil test calls for. Use a light hand: spread it evenly over the root zone and water it in; a typical soil-test rate for shrubs is about 2 lb of 12-6-6 per 100 sq ft (Clemson). Follow a soil test.

Too much fertilizer gives leafy growth with fewer flowers and makes kerria spread more aggressively (Morton Arboretum, NC State). For new plants, water daily for 2 weeks, every 2-3 days through week 12, then weekly until established (UMN).

Harvest

Blooms in late April and May, often around Easter, with scattered flowers through summer (Morton Arboretum, NC State). Flowers come on stems grown the year before, so cut back right after flowering; snip dead tips each spring, and every few years you can cut an overgrown plant to the ground after it blooms to renew it (Morton Arboretum, Oklahoma State).

Varieties (7)

NC State, the Morton Arboretum and Oklahoma State document these 7 cultivars.

Diseases and problems

Twig and leaf blight, Phomopsis stem blight, Septoria leaf spot, Cankers, Root rot

In the kitchen

Safety: The extension sources we used give no poison rating or toxicity warning for kerria. It is grown for looks, not food.

Pets: Not listed by the ASPCA (no kerria entry on its dog, cat or horse plant lists).