The Explorer's Garden: Rare and Unusual Perennials - Hardcover

Few gardeners who have cultivated the edible rhubarb (Rheum xcultorum) can deny that they have admired the columns of white flowers unfurling in globular splendor in early summer. But homage to such things in the vegetable garden is generally bittersweet, often but a swan song of yet another spring gone by — the end to a season of freshly picked and eaten produce. As a young gardener, in fact, I was taught to never let the blossoming stems emerge from our rather antique hand-me-down clump of "pie plant" that we grew on the far side of the vegetable patch. Advice well taken but, fortunately, not always heeded.

I only recently began growing true Rheum palmatum, a species native to China and, in its typical white-flowered form, infrequently cultivated. Having brought this back from a collecting foray to England, I use the plant to good effect in my light woodland, where it produces gigantic, Gunnera-like foliage in matte green and erect flowering panicles of white rising to 6 ft. (1.8 m) or higher. Certainly the best-known of the ornamental rhubarbs is this species's red-flowering cultivar, R. palmatum 'Atrosanguineum'. With a flair for the dramatic, 'Atrosanguineum' awakens in early spring with ruby-red foliage, which conjures nothing short of pure, unadulterated anticipation for what is to come. As the jagged leaves unfurl to nearly 3 ft. (0.9 m) across, the reddish tints of the upper surfaces take on a patina of aged copper, while the undersurfaces retain an intensity of matte rose-red. I am held spellbound in the early days of May when the fresh, upwardly held leaves, backlit by sun, capture and illuminate a palette of arresting colors and textures. Yet the show has only just begun, as in early June a massive flowering stem heads skyward, carrying large, knobby buds sheathed with scarlet bracts. After the stems reach upward to 7 ft. (2.1 m), the buds unfurl to create an airy spectacle of crimson flowers with cerise overtones. If good seed set occurs, an additional season of interest continues with numerous glossy red, triangular fruit dangling from this treelike inflorescence, Several other selected cultivars of R. palmatum are available, including 'Red Herald' and 'Hadspen Crimson' (both by Eric Smith) and 'Red Select'. I should mention that the distinctive foliage shape and color is more a product of patience than of simply acquiring a good clone. Foliage on young plants is less lobed and less colorful than on mature specimens.