Potentilla crassinervia: complete guide

Overview

Potentilla crassinervia, sometimes called Corsican cinquefoil, is a low-growing alpine perennial in the rose family (Rosaceae). The species was described in 1825 by the Italian botanist Viviani and grows exclusively in the mountain ranges of Corsica and Sardinia, particularly around the peaks of Monte Cinto and the Gennargentu massif. The species name "crassinervia" refers to the thick, prominent veins in the leaves, an adaptation to the harsh mountain climate this plant inhabits. In gardens, this rare cinquefoil is a sought-after subject for alpine plant enthusiasts and rock gardeners looking for something a little more special than the well-known Potentilla species. At gardenworld.app we increasingly see questions about this attractive, cushion-forming mountain plant for the sharply drained rock garden.

Appearance and bloom

The plant forms a compact, cushion-shaped mat 5 to 15 centimeters tall that slowly spreads to 20 to 30 centimeters wide. The foliage is composed of several small, rounded leaflets (typical of cinquefoils) in a silvery-green to blue-green shade, with the characteristic thick, prominently veined structure that gives the species its name. From July, elegant white flowers appear on short stems: five rounded petals surrounding a golden heart of stamens, typical of the genus Potentilla. Flowering peaks in August and, in favorable weather, continues into September. The compact growth habit and contrasting silvery foliage make this species a decorative addition to the rock garden even outside the flowering period.

Ideal location

Potentilla crassinervia wants a spot in full sun to light partial shade, with at least five to six hours of direct light daily. In its native habitat, the plant grows among boulders and on steep scree slopes at high altitude, where it withstands wind and temperature swings well. A raised scree bed, an alpine trough, or a crevice between limestone blocks in a dry wall are ideal spots. Ensure enough space around the plant for air to circulate freely; this prevents fungal issues on the dense cushion. Avoid fully sheltered, warm spots without air movement, since the plant is adapted to the cool, breezy conditions of its mountainous origin.

Soil

Sharp drainage is essential for Potentilla crassinervia. In the wild, the plant grows on gravelly, granitic scree low in nutrients, so a mix of coarse sand, grit, and a small proportion of humus-rich garden soil (for example 40 percent grit, 40 percent sharp sand, 20 percent garden soil) works best. Soil pH may range from slightly acidic to neutral, between 5.5 and 7.0, matching the granitic origin of its native range. Avoid limestone-rich, heavy ground and excessive fertilizing: too many nutrients produce a looser, less compact cushion. A layer of grit around the base keeps moisture away from the crown and prevents rot during wet spells.

Watering

During the growing and flowering period, from May to September, Potentilla crassinervia appreciates moderate, regular watering: keep the soil lightly moist without becoming waterlogged. In summer, during spells of prolonged heat, extra water may be needed to prevent the shallow root system from drying out. Once established, however, the plant is fairly drought tolerant thanks to its adaptation to rocky, fast-draining ground. In winter, almost no water is needed; excess moisture combined with frost is the main threat to this species. Use rainwater where possible, especially in areas with hard, limestone-rich tap water.

Pruning

Potentilla crassinervia requires minimal pruning. After flowering (September), remove the spent flower stems to keep the plant looking tidy and to limit self-seeding if desired. Old, faded leaves at the edge of the cushion can be carefully trimmed in early spring to make room for new shoots. On older mats that begin to thin in the center, a light division in spring can restore vigor: split the cushion into smaller sections and replant them immediately in a similar, well-draining mix. Heavy pruning is never necessary; the naturally compact growth habit is maintained on its own thanks to the species' slow growth rate.

Maintenance calendar

March-April: Check drainage after winter; divide older, thinning mats if desired.

May-June: Growth resumes; water regularly but moderately. Remove weeds around the cushion.

July-August: Peak flowering; plenty of pollinators. Water during prolonged drought.

September: Flowering fades; remove spent flower stems. Final light feeding if needed.

October-November: Winter preparation; check the grit layer around the base.

December-February: Winter dormancy; almost no maintenance needed beyond protection from prolonged freeze-thaw cycles.

Winter hardiness

As a mountain plant from Corsica and Sardinia, Potentilla crassinervia is quite winter hardy: the species survives temperatures down to roughly minus 15 to minus 20 degrees Celsius, corresponding to USDA zones 5 to 7. In gardens with milder, wetter winters, cold is not the greatest risk but rather prolonged winter moisture combined with frost. A covering of coarse grit around the crown keeps the base dry during winter rain. In snowy mountain regions, snow cover provides natural insulation; in lowland gardens without snow, well-draining ground is the best guarantee of winter survival. Young, newly established plants deserve extra attention in their first winter, and optionally a light covering of conifer branches.

Companion plants

Potentilla crassinervia combines excellently with other alpine species from similar mountainous habitats:

• Saxifraga species: rock plants sharing a similar preference for sharp drainage
• Sempervivum (houseleek): succulent rosettes providing contrasting structure
• Dianthus alpinus (alpine pink): pink flowers alongside the cinquefoil's white
• Armeria maritima (thrift): compact cushions with pink flower heads
• Silene acaulis (moss campion): a similarly cushion-forming growth habit
• Gentiana species: intensely blue flowers as a color accent

Plant these species together in a well-draining scree bed for a lively alpine tapestry.

Closing

Potentilla crassinervia is a modest yet genuinely special find for anyone wanting to enrich their rock garden with an authentic mountain cinquefoil from Corsica and Sardinia. With its silvery-green, prominently veined foliage and elegant white flowers from July to September, this species offers months of decorative value without demanding much upkeep. Seed and young plants are rarely found at an ordinary garden center; consult specialized alpine nurseries or seed exchanges run by rock garden societies for the best chance of finding this species. Grit, sharp sand, and alpine potting mixes for the right growing medium are, however, readily available at any well-stocked garden center. At gardenworld.app we keep a growing overview of rare, winter-hardy mountain plants like this one, so your own rock garden can benefit from their subtle beauty.