Kirengeshoma palmata: A Woodland Perennial with Elegant Late Summer Flowers
Kirengeshoma palmata is a Japanese perennial with bold foliage and late summer flowers. It’s located at the southern end of the Seattle Japanese Garden – near the less-traveled path that parallels the garden’s western edge. With bold maplelike leaves and substantial size, it looks like a shrub. Nevertheless, it has herbaceous foliage that dies back to the ground in winter. Most woodland perennials are spring-blooming – so with its exotic appearance & late summer flowers, it’s a valuable addition to our gardens.
The genus name, Kirengeshoma, is derived from the Japanese words, ki renge shoma. Ki means “yellow,” and renge shoma refers to Anemonopsis macrophylla (false anemone), a perennial that it somewhat resembles. In English, it’s known as yellow wax bells – a reference to its yellow, waxy-looking, bell-shaped flowers.
Kirengeshoma palmata is native to cool, mountainous areas of Shikoku and Kyushu – and according to some authorities, northeast China as well. There is also a Korean form. In the wild, it’s found growing in steep woodland areas with loose, rocky soil. Surprisingly, Kirengeshoma is in the family Hydrangeaceae, although its flowers are much smaller and less showy than those of the more familiar hydrangeas. In size and leaf shape – but not flowers – it reminds us of Abutilon, known as flowering maple, in the family Malvaceae.
Shrublike in stature, yellow wax bells grows from short, thick rhizomes, but is not considered invasive. It generally matures at 3-4 feet tall by 2-3 feet wide, although very old clumps will often be much wider. The large, coarsely-toothed green leaves (to 8 inches wide), are maplelike and deeply cut into 7-10 lobes – hence the species name, palmata. This is a reference to its leaf shape, which resembles a human palm. Similarly, Acer palmatum is the botanical name of Japanese maples, which also have palmlike foliage. The leaves of Kirengeshoma are held opposite each other on the stems – greenish or sometimes purplish in color.
Delicate-looking, pendulous flowers open in late summer from small rounded buds that look like yellowish-white balls capped in green. After elongating, they open to nodding, trumpet-shaped flowers in loose clusters of three, at or near the ends of arching leaf stems. Pale yellow, about 1.5 inches long and waxy in texture, they are narrowly bell-shaped – and never open fully before they’re shed.
As shown above, the fruits that follow are round seed capsules with three horns. According to perennial authority Allan Armitage, “Waxbells produce the ‘Stephen King of fruit.‘ Three long painted horns protrude from a brownish green swollen capsule; the effect is enough to cause a nightmare!” Another commentator describes them as “grotesquely interesting.” To me, they look like something from outer space!
Kirengeshoma palmata grows in cooler areas of Japan and benefits from that country’s rainy summers. It is hardy to USDA Zones 4 or 5 (minimum temperature -30 or -20 degrees F). Plants grow best in part to full shade, in moist, well-drained, humus-rich acid soils. They may attract slugs when emerging in spring but have no serious insect or disease problems.
Plants native to Korea are sometimes considered a separate species, K. koreana – or simply a form of Kirengeshoma palmata, known as K. palmata Koreana Group. They tend to be larger than the Japanese form, but have smaller leaves, upward or outward-facing flowers and greenish stems.
Kirengeshoma palmata is a large perennial that’s usually grown as much for its imposing stature and exotic foliage as for its delicate flowers. Its bloom time, however, is unusual for a woodland perennial and brings a touch of luminous, late summer color to shady areas of our gardens. When planted in the conditions it prefers, Kirengeshoma is long-lived and easy to grow and propagate – by division, cuttings or seeds. The soil in my own garden is less than ideal, but it grows happily there in a large container.
Corinne Kennedy is a Garden Guide, frequent contributor to the Seattle Japanese Garden blog, and retired garden designer.