There are around 300 species of hardy Geranium (not to be confused with bedding geraniums, which are actually in the genus Pelargonium), a group of perennials and subshrubs in the geranium family (Geraniaceae). Many of these have been used as medicinal herbs and as attractive ornamentals for the temperate garden. G. xcantabrigiense is a natural hybrid of G. macrorrhizum and G. dalmaticum that is hardy in zones 5-8. The cultivar ‘Biokovo’ – discovered in the Biokovo Mountains in Croatia on the Dalmation Coast of the Mediterranean – has been selected as the Perennial Plant Association’s Perennial of the Year 2015. Many gardeners report that this cultivar survives reliably in zone 4.
‘Biokovo’ forms low, spreading mounds of bright medium green foliage growing 6 to 12” high. The aromatic (with a fruity, almost lemony fragrance), slightly glossy leaves are rounded and divided into 7 toothed lobes, and can be up to 3” across. In the fall the foliage can become a brilliant red to coppery orange, but the leaves do not die back as it is nearly evergreen in most climates. This is a rhizomatous plant so it slowly spreads to form patches 2 to 3 feet wide, but the runners extend further than those of the original hybrid, so it does not form as dense a carpet of foliage.
In mid to late spring through mid- summer clusters of delicate but showy flowers are produced above the leaves. The flowers of this cultivar are white tinged with a pink flush at the base of each petal. Each ¾ to 1 inch wide flower has 5 reflexed petals and showy pink stamens that dance with the slightest breeze. The petals often have pale pink striations. The occasional flower may be produced in summer or fall, too. The flowers are attractive to butterflies and bees.
As a low-growing, spreading plant ‘Biokovo’ makes a good ground cover and will naturalize under ideal conditions. It is excellent in masses, and can be used in the front of borders or in the cottage garden, as an edging plant, or in rock gardens where the short plants with fine texture can be appreciated. It works in dry light shade (although may not flower if too shady) and on slopes to prevent soil erosion. It can even be used in containers, but may not survive the winter if left unprotected in the container in harsh winters. Combine it with spring-flowering bulbs so the foliage will disguise the ripening bulb foliage after flowering. They make good filler plants, blending nicely with most other perennials. Try it in combination with lady’s mantle (Alchemilla mollis), Siberian iris, and lamb’s ear (Stachys byzantina). Or place ‘Biokovo’ near plants with purple leaves or grassy foliage for maximum contrast in color and texture.
This geranium is a low maintenance plant, requiring little care when grown in full sun to part shade and average, well-drained soil. In hot climates it is best positioned to get morning sun and some shade during the hottest part of the day, but it tolerates full sun in cooler climates. Because it is a spreading plant, it may need to be thinned to keep it confined to a specific space, but it is easy to pull up where it is not wanted, so is not considered invasive. It is not favored by deer, rabbits, or slugs, and has few other pest problems. It can be sheared in spring to improve the appearance of the plant and after bloom to stimulate limited reblooming, but this is not essential. Propagate by division in spring or fall.
Other cultivars of G. xcantabrigiense include:
- ‘Cambridge’ – has deep pink to magenta flowers
- ‘Cambridge Blue’ – has lavender-blue flowers
- ‘Karmina’ – has rose pink flowers
- ‘St. Ola’ – has white flowers
– Susan Mahr, University of Wisconsin – Madison
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- Geranium x cantabrigiense ‘Biokovo’ – on the Missouri Botanic Garden’s Kemper Center for Home Gardening website