Geranium macrorrhizum aka Rock Crane's Bill

Geranium macrorrhizum is known as bigroot geranium or cranesbill. It belongs to the geranium family, Geraniaceae. This perennial comes from central and southeastern Europe to western Türkiye. It grows in woods, scrub, and rocky limestone sites. Wild plants also grow on mountain screes and in shade. It is not native to Britain or Ireland.

Thick rhizomes spread to make a dense, low mat. The plant keeps some of its leaves through winter. Garden plants reach about 1–1.6 feet [0.3–0.5 metres] tall. Their spread reaches about 2–3.3 feet [0.6–1 metre]. The rounded leaves have deep lobes and toothed edges. Their colour ranges from grey-green to deep green. Leaves feel sticky and give off a strong scent when crushed. They can turn red in autumn, with strong colour in sun.

Pink to purple-pink flowers rise on stems above the leaves. Each bloom measures about 1–1.2 inches [2.5–3 centimetres] across. Dark red calyces surround the flowers, which grow in clusters. Bloom runs from May to July, though some sources give May to June. A few more flowers may appear later in summer. The blooms attract butterflies. The foliage gives ground cover value beyond the main bloom season.

Grow this plant in soil that drains well. It accepts clay, chalk, loam, and sand across a wide pH range. It grows in sun or shade, including dry shade. Afternoon shade helps in places with hot summers. Thick rhizomes help it cope with drought. Avoid soil that stays waterlogged. Sources list USDA zones 4–8, with Chicago also listing zone 3. The RHS gives it a UK hardiness rating of H7. Divide plants in spring, or take basal cuttings then.

Use it beneath trees and shrubs or along border edges. Its dense growth helps keep weeds down and can limit erosion. Deer and rabbits tend to leave it alone. Remove spent flower stems and old or yellow leaves. Routine shearing after bloom is not needed. Serious pest problems are uncommon, but vine weevils, capsid bugs, and sawflies may occur. Downy and powdery mildew can also affect it. Its scented leaves have served in perfume and pot-pourri. PFAF reports no known edible uses or hazards. It also records a traditional aphrodisiac use, without evidence here of benefit.