Cranesbill (Geranium 'Johnson's Blue')

Overview

Geranium ‘Johnson’s Blue’ is celebrated as one of the most appealing blue-flowered Cranesbill varieties available for the garden. This robust, rhizomatous perennial forms a dense, spreading mound smothered in large, saucer-shaped flowers that open to a brilliant sky blue color. Its extended bloom period, often lasting from late spring well into fall, provides consistent color where other perennials might falter.

As a popular choice since its introduction in the 1950s, Geranium ‘Johnson’s Blue’ offers exceptional reliability and ease of care. It is highly valued for its versatility, thriving equally well as a grounding element in borders or used en masse for ground cover applications. Gardeners appreciate its low maintenance requirements combined with its striking visual impact.

The deep green, finely cut foliage offers an excellent textural contrast to the bright blooms, making this Cranesbill attractive even when not in flower. With good drought tolerance once established, Geranium ‘Johnson’s Blue’ is an invaluable addition for creating layered, long-season interest in the mixed perennial border.

Fast Facts

• Plant Family: Geraniaceae
• Plant Type: Herbaceous perennial
• Hardiness Zones: USDA Zones 4-8
• Size at Maturity:
  • Height: 1-1.5 ft
  • Spread: 2-2.5 ft
• Bloom Time: June to September
• Bloom Description: Blue
• Sun Exposure: Full sun to part shade
• Water Needs: Medium
• Maintenance Level: Low

How to Grow

Planting Cranesbill is best accomplished in spring or fall after the danger of hard frost has passed. Locate Geranium ‘Johnson’s Blue’ where it receives average, well-drained soil; while adaptable, it truly prefers moist, organic soil conditions for optimum performance. It tolerates full sun but benefits significantly from some afternoon shade, especially in hotter climates where midday exposure can lead to bloom interruption.

Watering should remain consistent, aiming for medium moisture, particularly until the plant is fully established in its new location. Once mature, established plants exhibit some helpful drought tolerance, though supplemental watering during prolonged dry spells will maintain vigorous growth and continuous flowering. Fertilization is rarely necessary if the soil is rich in organic matter.

Pruning is a key low-maintenance task for this plant. If the primary bloom slows down during intense summer heat, cutting the plant back—even quite hard—will rejuvenate the foliage and encourage a second, lighter flush of blooms continuing into the fall. Non-flowering side stems can also be trimmed at any point to help control spread and maintain desired garden shapes.

For northern gardeners, Geranium ‘Johnson’s Blue’ typically maintains a steady bloom throughout the summer and into fall without significant interruption due to heat stress. Ensure good air circulation around the plants to minimize the slight susceptibility to common fungal issues like leaf spots or rusts.

Landscape Uses

The dense, spreading habit of Cranesbill makes Geranium ‘Johnson’s Blue’ an outstanding choice for mass planting, effectively acting as a living mulch or ground cover throughout sunny borders and naturalized areas. Its 2 to 2.5-foot spread allows it to effectively suppress unwelcome weeds once established.

For dynamic cottage gardens or structured perennial borders, this cultivar provides exceptional textural contrast. Use its mid-height stature to anchor taller plants while allowing lower-growing species to spill over edges. It performs beautifully in rock gardens, softening hard lines with its mound of finely dissected foliage.

Beyond the garden bed, Geranium ‘Johnson’s Blue’ adapts well to containers. Combine it with upright annuals or summer bulbs; its low-mounding form acts as an excellent ‘thriller’ or ‘spiller’ depending on container height. Remember to provide consistent moisture when growing in pots, as containers dry out much faster than in-ground settings.

Standout Features

Flower Qualities

• Showy

Noteworthy Characteristics

Geranium is a genus containing about 300 species of annuals and herbaceous perennials originating from temperate regions, providing gardeners with many excellent hybrid selections. The genus name originates from the Greek word geranos, meaning crane, referring to the elongated fruit structure that resembles a crane’s head and beak. Geranium ‘Johnson’s Blue’ is highly popular for its consistent, large, saucer-shaped sky-blue flowers that bloom profusely above deep green foliage from late spring through early fall. This rhizomatous perennial typically forms a dense mound, growing 12 to 18 inches tall and spreading up to 30 inches wide.

Tolerances

• Rabbit
• Deer

Potential Problems

This particular Cranesbill generally exhibits remarkable resilience, suffering from few serious insect or disease issues under normal cultivation. Gardeners should remain observant for occasional susceptibility to foliar issues such as rusts or various types of leaf spot, especially in areas where air circulation is poor or soil drainage is inadequate. To minimize the risk of fungal development, ensure the plants are not overcrowded, and water at the base of the plant rather than overhead, particularly later in the day. Promptly trimming away any discolored leaves can keep the plant looking fresh through its long blooming season.

Frequently Asked Questions

What hardiness zones is Cranesbill suitable for?

Geranium ‘Johnson’s Blue’ is reliably hardy in environments coded USDA Zones 4 through 8.

How large does Geranium ‘Johnson’s Blue’ grow?

This perennial typically reaches a mature height between 1 and 1.5 feet tall, spreading outwards to a width of 2 to 2.5 feet.

When does Cranesbill bloom?

You can expect consistent blue flowering from this variety primarily during June, July, August, and September under favorable conditions.

What sun exposure does Geranium ‘Johnson’s Blue’ need?

This Cranesbill performs best when situated in an area receiving full sun or partial shade, making it adaptable for many garden locations.

Conclusion

Geranium ‘Johnson’s Blue’ stands out due to its long-blooming nature, attractive blue coloration, and low-maintenance requirements, making it a staple for reliable summer impact. This excellent Cranesbill cultivar provides superb coverage and texture, enhancing nearly any perennial planting scheme. Before planting, confirm your local hardiness zone compatibility and amend your soil to ensure it is moist and well-drained for the best seasonal performance.

Propagation Tips

Propagation of Geranium ‘Johnson’s Blue’ is straightforward, mainly achieved through division of the rhizomes. Division should ideally take place in the early spring just as new growth emerges, or in the early fall after the main summer heat subsides. Dig up the clump and gently separate large chunks of the root mass, ensuring each section maintains several healthy growth points or buds. Replant these divisions immediately at the same depth they were previously growing and water thoroughly to help reduce transplant shock and encourage rapid reestablishment.

Companion Planting

Due to its preference for medium moisture and its ability to handle part shade, Geranium ‘Johnson’s Blue’ pairs wonderfully with plants that share similar cultural needs. Consider planting it alongside Hosta varieties that have lighter green or variegated foliage to contrast the dense, dark leaves of the Cranesbill. It also combines nicely with Japanese Forest Grass (Hakonechloa macra) for textural contrast or taller spring-blooming bulbs like Alliums, which will emerge and bloom above the spreading Geranium foliage before the summer heat peaks.