Hardy Geraniums: A Comprehensive Guide to Cultivation and Care
Botanical Overview
Hardy geraniums, also known as cranesbill geraniums, comprise a diverse group of herbaceous perennials belonging to the Geranium genus. They are characterized by their low-growing, dense, carpet-like foliage and distinctive cupped-shaped flowers that bloom in a variety of shades. Hardy geraniums are popular garden plants due to their hardiness, adaptability, and long-lasting blooms.
Types of Hardy Geraniums
There are numerous types of hardy geraniums available for cultivation, each with unique characteristics and growth habits. Some popular varieties include:
- Geranium ‘Johnson’s Blue’: Known for its sky-blue flowers and compact growth habit.
- Geranium sanguineum: Features reddish-purple flowers and clumping foliage.
- Geranium himalayense: Produces violet, indigo, and blue flowers in mid-summer.
- Geranium × oxonianum ‘Wargrave Pink’: A vigorous hybrid with salmon-pink flowers.
- Geranium ‘Gerwat’ Rozanne: A prolific bloomer with violet-blue flowers that bloom almost non-stop throughout summer.
Propagation and Cultivation
Propagation: Hardy geraniums can be propagated through division or from seed. Division is the preferred method for preserving desirable traits in cultivars.
Growing from Seed: Seeds can be sown directly in the garden in early spring or started indoors in seed trays. However, germination can be slow and seedlings may take several years to reach maturity.
Potting: Hardy geraniums are not typically grown in containers, but they can be successfully grown in oversized pots with well-draining potting mix. Water sparingly and fertilize lightly.
Overwintering: Hardy geraniums are generally cold-hardy and do not require winter protection. However, in colder climates, it is advisable to cut back stems to just above ground level to remove potential sources of disease.
Common Pests and Diseases
Hardy geraniums are relatively resistant to pests and diseases, but they can occasionally be affected by:
- Slugs
- Mildew
- Rust
Bloom Care
Hardy geraniums typically bloom from early summer to early fall. To encourage continuous blooms, consider the following:
- Ensure adequate sunlight exposure (at least six hours per day).
- Avoid overwatering, as excessive moisture can inhibit blooming.
- Avoid over-fertilizing, as high levels of nitrogen can promote foliage growth at the expense of flowers.
Troubleshooting Common Problems
- Sparse foliage or leggy growth: Shear or cut back after flowering to stimulate new growth.
- Poor blooming: Check for inadequate sunlight, overwatering, or excessive fertilization.
- Invasive growth: Hardy geraniums can spread rapidly in some conditions. Dig out unwanted plants if necessary.
Landscaping Uses
Hardy geraniums are versatile plants that can be used in a variety of landscaping applications:
- Border Plants: They make attractive edging plants due to their compact growth habit.
- Woodland Gardens: Certain varieties thrive in partial shade and can add color to woodland landscapes.
- Rock Gardens: Hardy geraniums are well-suited to rock gardens and can provide ground cover between rocks.
- Mixed Perennial Beds: They weave well among other plants and can help suppress weeds.
Distinction from Pelargoniums
Despite being commonly known as geraniums, Pelargoniums belong to a different genus. They are not hardy and require different care, including protection from cold temperatures.
Indoor Cultivation
Unlike Pelargoniums, hardy geraniums are not suitable for growing indoors as houseplants. They require a dormant winter chill period that cannot be replicated indoors.