Petasites japonicus 'Giganteus'

This Giganteus Petasites is a vigorous trailing rhizomatous perennial plant that thrives in shady and humid environments. Its globular flower heads, resting on a collar of pale green bracts, stretch upwards into spikes adorned with petite, fragrant, cream-coloured flowers in spring before the foliage appears. Then, large leaves with more or less dentate margins and undulated edges, measuring over 1m (3ft) in diameter, emerge. It is interesting to bring a touch of luxuriance to the wet and barren areas of a large garden, but its tendency to spread must be contained. This plant prefers humus-rich soils and dislikes scorching sun.

The japonicus Petasites is a plant native to China, Korea, and Japan. The Japanese Petasites form a vigorously spreading clump reaching 50 to 120cm (20 to 47in) but spreading indefinitely through its robust trailing rhizome—the plant flowers in March-April before the leaves appear. Emerging from grey leaves, the flower heads emerge from the ground, carried by a leafy stem, whose leaves are alternate, elongated, pointed, sessile, and very different from the large basal leaves that will appear after flowering. The flower head forms an elliptical and compact cluster, 10 to 25cm (4 to 10in) high. It consists of small female or male heads gathered in panicles. The pale green and white flowers, surrounded by light green bracts with a diameter of 1cm (0in), emit a sweet fragrance reminiscent of honey. The caducous basal foliage appears later. It consists of large kidney-shaped leaves with a rounded, veined, undulate lamina measuring 0.5 to over 1m (3ft) diameter. Their colour is a satin greyish green, and the upper surface is covered in downy hairs. They are bordered by a more or less dentate margin and attached to the rhizome by a long petiole consumed as a vegetable in Japan.

The Giant Japanese Petasites is a fast-growing plant, useful for adding a touch of lushness to the boundaries of a very large garden, covering a ditch, a fresh rockery, or a very humid understory that has been neglected. It will release its fragrance even in the garden's more 'civilised' areas and brighten a slightly dark corner. However, care must be taken to ensure it does not exceed the allotted limits, as it disregards property boundaries and the rules of civility between neighbours. As it loves humidity and dislikes the sun, one can try to contain it effortlessly by creating a dry rockery in its path, where the sun prevails over the shade. It can be paired with Lysichitons, Marsh Irises, Solomon's Seals, and well-established peonies.