Butterbur, Petasites japonicus: “Waterside Posy”
Petasites japonicus is a decorative waterside plant that dies down in winter, reemerging as cabbage-like posies that are ready to go when everything else is just waking up. As a ground cover, it is certainly effective by summertime, when four-foot leaves form an impenetrable thicket.
Happiest when they have wet feet, Petasites japonicus thrives on river banks and at the edges of marshes, where we recently discovered some lovely specimens in bloom. We wandered among pale rosettes that emerged above the mud like a galaxy of cauliflowers.
Photography by Britt Willoughby Dyer, for Gardenista.
If you happen to have a large property with a featureless bank next to water, in shade, then this is the plant for you. The effect is similar to that of gunnera in summer: in other words, giant (round) leaves that can be admired up close but not wandered through.
The natural habitat of Petasites japonicus is a mountainside stream in East Asia. Their roots make a kind of net, binding the slippery landscape together.
So captivating are these pale bouquets that visitors to the Beth Chatto gardens in Essex in the east of England have had to be gently dissuaded by observant staff from taking them home to decorate their rockeries. Known as the giant butterbur, Petasites japonicus var. giganteus needs space.
This plant defines the Beth Chatto philosophy of “right plant for the right place.” In her book The Damp Garden, a chapter discussing the places of origin of her community of garden plants is a persuasive argument for this philosophy, and lyrically written.
- Depending on the variety, butterbur’s flowers can be a soft pink or cauliflower white.
- Plant butterburs en masse on a shady, wet slope to prevent erosion.
- A cousin, Petasites hybridus also thrives in marshy situations but has large round leaves and pale pink flowers.
Keep It Alive
- In wet soil, butterburs will thrive in USDA growing zones 4 to 9.
- Butterburs prefer sandy, loamy soil or clay.
- You can expect butterburs to spread by underground rhizomes to form a dense ground cover.
For more growing tips, see Butterburs: A Field Guide to Planting, Care & Design in our curated Garden Design 101 guides to Perennials 101. For more plants that thrive in moist conditions, see:
- The Poet and His Garden: Ian Hamilton Finlay in Scotland
- Beth Chatto’s Garden: Shade-Loving Plants for Year-Round Interest
- 10 Garden Ideas to Steal from Ireland
- Ground Covers 101: A Field Guide to Planting, Care & Design