Cranesbill (Geranium macrorrhizum)

Overview

Geranium macrorrhizum, widely known as Cranesbill, is a highly valued, rhizomatous, semi-evergreen perennial perfect for tackling difficult spots in the landscape. It forms a dense, weed-suppressing ground cover thanks to its thick, spreading roots. This robustness is paired with beautiful, long-lasting blooms appearing from late spring through mid-summer.

This particular species of Cranesbill is exceptionally tolerant of adverse conditions, handling hot and humid summers better than many other geraniums, and establishing quickly even on dry slopes. Its grayish-green, aromatic foliage provides excellent textural contrast, often developing attractive red tones in the fall.

The practical benefits of Geranium macrorrhizum make it a gardener’s staple: it requires low maintenance, offers superior drought tolerance once established, and effectively resists browsing pressures from common garden pests. Planting this tough ground cover ensures reliable, attractive coverage year after year.

Fast Facts

• Plant Family: Geraniaceae
• Plant Type: Herbaceous perennial
• Native Range: Southern Europe, Turkey
• Hardiness Zones: USDA Zones 4-8
• Size at Maturity:
  • Height: 1-1.5 ft
  • Spread: 1-2 ft
• Bloom Time: May to July
• Bloom Description: Purple pink
• Sun Exposure: Full sun to part shade
• Water Needs: Dry to medium
• Maintenance Level: Low

How to Grow

The best time to plant Geranium macrorrhizum is when conditions are mild, generally spring or fall, ensuring the plant establishes its deep, drought-resistant rhizomes with minimal heat stress. It thrives in average, well-drained soil. While it handles full sun, especially in cooler summer regions, gardeners in hot climates should locate this Cranesbill where it receives some afternoon shade to prevent potential leaf scorch.

Water requirements are minimal once this plant is established; it tolerates true drought conditions. Fertilizing is usually unnecessary as this species seeks natural vigor. Maintenance is exceptionally low for Geranium macrorrhizum. Unlike some perennials, it rarely needs heavy pruning. If the foliage starts to look tired mid-summer, simply snip off yellowing individual leaves.

Flowering stems generally do not require shearing or hard cutting back after the main bloom concludes. The plant spreads readily via its rhizomes, quickly filling spaces to create that desired weed-suppressing mat. While it can self-seed, propagated stock or division is recommended to maintain specific cultivar traits. Clumps are easily divided in spring or fall if you need to rejuvenate the patch or spread the plant around the garden.

Landscape Uses

The primary appeal of this Cranesbill lies in its function as an outstanding, tough ground cover. Geranium macrorrhizum is ideal for naturalizing under trees or on slopes where other plants struggle due to dry shade or foot traffic. Its spreading habit makes it a perfect filler for border fronts, softening hard edges and providing season-long structure.

For cottage gardens or wild settings, this dependable perennial integrates seamlessly, pairing well with spring bulbs that finish blooming before the Cranesbill fully covers the ground. Its textural foliage contrasts nicely with fine-textured ferns or bold hostas that can tolerate similar light levels. Consider using it in mass plantings to create an uninterrupted swath of color in late spring.

Its resilience against deer and rabbits also makes Geranium macrorrhizum a reliable choice for less protected areas of the garden or naturalized borders where wildlife browsing is common. Its ability to tolerate dry soil ensures success where irrigation is sparse.

Flower Qualities

• Showy

Noteworthy Characteristics

Geranium macrorrhizum, commonly called bigroot geranium, is a rhizomatous semi-evergreen perennial that typically grows to 12” tall but spreads to 24” wide to form a thick, weed-resistant ground cover. Deeply lobed and rounded, grayish-green leaves have 5-7 lobes, with each lobe having 3 to 5 notches at the tip, and are strongly aromatic when crushed. Long-lasting purple-pink flowers bloom in clusters above the foliage in late spring to early summer, often with sporadic rebloom throughout the season.

Tolerances

• Rabbit
• Deer
• Drought
• Erosion
• Dry Soil

Potential Problems

The good news for gardeners is that Geranium macrorrhizum generally suffers from no serious insect or disease problems. Its inherent toughness means it is resistant to many common stresses that plague more delicate perennials.

Avoid planting it in areas with consistently wet or poorly drained soil, as heavy, soggy conditions are the primary threat to rhizomatous health, which can lead to root rot. Proper placement in well-drained soil, accounting for its drought tolerance, is the best preventative measure.

Frequently Asked Questions

What hardiness zones is Cranesbill suitable for?

Geranium macrorrhizum is reliably hardy across USDA Zones 4 through 8, making it adaptable to many varied climates.

How large does Geranium macrorrhizum grow?

This perennial typically reaches a mature height of 1 to 1.5 feet and spreads horizontally to cover an area between 1 and 2 feet wide.

What sun exposure does Cranesbill need?

This plant performs best when given a location that receives full sun to partial shade. In intense summer heat, a bit of afternoon shade is appreciated.

When does Cranesbill bloom?

You can expect the attractive purple-pink flowers of this Cranesbill variety to appear throughout the late spring and early summer, typically from May through July.

Conclusion

The unparalleled toughness and low input required make Geranium macrorrhizum an essential component for sustainable landscape design. Its ability to form a dense, aromatic, weed-suppressing mat cements the value of this particular Cranesbill species. Assess your drier, less convenient garden spaces and plan to install Geranium macrorrhizum this coming season for reliable, effortless coverage.

Propagation Tips

Division is the easiest and most predictable way to propagate established clumps of Geranium macrorrhizum. Wait until early spring before new top growth emerges, or utilize the fall season after flowering concludes. Simply dig up a section of the mature plant, ensuring the clump has several healthy rhizomes attached, and replant immediately into the desired location. This method guarantees the new plants will be true to the parent stock.

Because this species spreads reliably by rhizomes, dividing the plant also serves as a mild rejuvenation technique for overcrowded patches. Removing sections helps prevent the center of older clumps from thinning out over time. Ensure any divided piece has viable roots attached, as the root system is key to its rapid establishment and drought tolerance.

Companion Planting

When selecting companions for Geranium macrorrhizum, focus on plants that share its preference for dry to medium soil conditions and thrive in similar sun exposures (full sun to part shade). This longevity allows for multi-season interest.

Consider pairing the spring bloom of this Cranesbill with plants that emerge later or die back sooner, filling the gaps effectively. Plants like Sedum varieties, especially those that prefer dryer spots, or ornamental grasses that appreciate the light shade the Cranesbill provides in the height of summer, make excellent partners.

For lower light conditions where the Cranesbill is shaded in the afternoon, consider hostas or hellebores, provided the soil drainage remains adequately sharp, which is crucial for the success of established rhizomes.