Plant profile: Sanguisorba
Long flowering, hardy perennials that are easy to grow and perfect for adding an airy feel to borders
Once, while wandering over the chalk downs of Box Hill in Surrey, I noticed the delicate scent of cucumber. On inspection of the ground beneath my feet I discovered I was standing on a diminutive pinnate-leaved plant that had small, globular, greenish-red heads with long straggly stamens: the salad burnet ( Sanguisorba minor). This was my first encounter with one of the two British native burnets, the other, the great burnet ( Sanguisorba officinalis), preferring moisture-retentive soils in meadows or at the edge of woodland. It is much taller at 1.2m with small, burgundy bobbles atop wiry stems.
Burnets are found throughout Europe, Asia, Japan and North America. On a plant-hunting expedition to Korea in 1993 with James Compton, John d’Arcy, and John Coke, we collected several seed samples from various Sanguisorba species possibly akin to Sanguisorba officinalis and Sanguisorba tenuifolia among others. Their horticultural importance is that it appears that the further east the plant was collected the later the flowering time. In Europe, Sanguisorba officinalis usually blooms in late June and July, whereas our collections from Korea were at their peak in August and September. Sanguisorba ‘Cangshan Cranberry’, collected in Yunnan in southwest China by Dan Hinkley, flowers as late as October and November in some seasons. With the propensity for hybridisation within this genus many garden-worthy burnets have been named but in such large numbers that a trial to evaluate the many species and cultivars is currently being undertaken at RHS Garden Wisley.
Burnets are particularly suited to naturalistic plantings, and different hybrids flower throughout the season from late April to November. There are several methods of pollination within this genus. Sanguisorba minor and Sanguisorba tenuifolia var. alba are wind pollinated with long stamens so that pollen is easily wafted away in the breeze. These species and hybrids are rarely scented and tend to be greenish or white. Others, such as Sanguisorba officinalis with its compact burgundy burrs, are mainly pollinated by flies, while the fat catkins of Sanguisorba hakusanensis and its hybrids are sweetly scented and brightly coloured – the Barbara Cartlands of the plant world – in vivid pink or magenta that attracts butterfly pollinators in their native habitats.
As all species and hybrids readily hybridise these features get thoroughly mixed up in the resulting progeny. Growing several different burnets in close proximity has produced some wonderful hybrids such as those at Sussex Prairies where substantial specimens of Sanguisorba ‘Blackthorn’ with upright tapers of smoky pink flowers are cheek by jowl with other sanguisorbas and are likely parents to the Sussex Prairies hybrids: ‘ Sussex Prairies Cheyenne’, ‘ Sussex Prairies Navaho’, ‘Sussex Prairies Iroquois’ and ‘Sussex Prairies Apache’.
Sanguisorba canadensis is a robust plant with strong stems growing to 1.5m, and flowers in late summer with vertical candles of greenish-white opening to pure white as the flowers mature. How I would love to see a red or deep-burgundy flowered burnet with 15cm-long candles, such as those displayed by Sanguisorba canadensis, but with the propensity for hybridisation – watch this space.
Burnets are not all about flowers; their foliage contributes greatly to the naturalistic border with handsome pinnate foliage and toothed margins to the leaflets. Mounds of glaucous-green foliage on Sanguisorba armena are somewhat reminiscent of that of Melianthus major. White catkin-like flowers with black stamens, which are best removed as they detract from the foliage effect, appear late in the season. It spreads by suckering and can colonise large areas, whereas the well-behaved Sanguisorba obtusa ‘Chatto’ is compact with grey-green leaves.
Subtle and charming Sanguisorba species and hybrids grow easily in any moderately fertile soil that is moisture-retentive and does not get overly dry or waterlogged. They have excellent foliage, are not prone to pests and diseases and can provide many months of interest.
• Marina Christopher is a nurserywoman who runs Phoenix Perennial Plants.
Her recommendations for the best sanguisorbas can be found over the next five pages.