There is a great deal of variety in the Geranium genus, but most of the commonly grown species are low-growing, dense, carpet-like plants with flower stalks that poke and weave through neighboring plants. The flowers float on top of the plant in shades of white, pink, magenta, purple, and blue. The flowers are small—around 1 inch—and cupped-shaped, attracting plenty of butterflies and bees. Cranesbill geraniums are usually planted from potted nursery plants in the spring, but they can also be divided and replanted through early summer. Nursery plants or divisions will quickly reach flowering maturity within in their first year, then slowly spread to fill available space. Plants started from seed, however, can take several years before they flower. Plant hardy geraniums so that the crown of the plant is at ground level or slightly above. Planting too deep can prevent them from flowering. Cutting them back after flowering often prompts repeated blooms into late summer and early fall. .
Light
Hardy geraniums accept a wide range of exposure conditions. For the best flowering and most vigorous geranium plants, site them in full sun to part shade. If geraniums are grown in hot, full sun, provide regular water. Some varieties of geraniums can tolerate full shade, but they likely won’t blossom as fully as those that have plenty of sun.
Soil
Geraniums are not particular about soil pH, but a neutral to slightly acidic soil is ideal. Most prefer medium-moisture, well-drained soil, though some species prefer relatively dry soil.
Water
Geraniums are a low-maintenance plant, so water them only when the soil gets dry. If located in full sun, water the plant more frequently. Hardy geraniums can become prone to fungal disease if watered overhead.
Temperature and Humidity
Hardy geraniums grow best in daytime temperatures between 65 and 75 degrees Fahrenheit and nighttime temperatures between 50 degrees and 60 degrees. They tolerate a wide range of humidity levels, though mildew and rust can be a non-life-threatening issue in very humid regions.
Fertilizer
Unless the soil is very poor, hardy geraniums generally do fine with no feeding other than a yearly application of compost. Poor soils may require a spring feeding with a time-release balanced fertilizer.
Types of Hardy Geranium
There are as many as 300 types of geraniums available to grow, some that are pure species, others that are nursery-created hybrids. Some popular choices include:
Geranium ‘Johnson’s Blue’: This variety is thought to be a hybrid between G. himalayense and G. pretense. It is one of the most popular of all varieties, growing about 18 inches tall with sky-blue flowers. It is suitable for zones 4 to 8.Geranium sanguineum: This species, sometimes known as bloody cranesbill, is a relatively low-growing, clumping form that produces reddish-purple flowers from May to June, with lesser flowering into the late summer. It is grown in zones 3 to 9. Several good cultivars are available: ‘Album’, with white flowers; ‘Elke’, with soft pink flowers; and ‘New Hampshire Purple’, which has violet flowers with white eyes.Geranium himlayense: Known as lilac cranesbill, this species is hardy in zones 4 to 8 and produces violet, indigo, and blue flowers in early to mid-summer. It grows 9 to 18 inches in height.Geranium × oxonianum ‘Wargrave Pink’: The most commonly grown geranium with salmon-pink flowers, it grows 18 to 24 inches tall in zones 3 to 8.Geranium ‘Gerwat’ ROZANNE: A violet-blue hybrid that flowers almost non-stop throughout summer. it grows 18 to 24 inches tall in zones 5 to 8.Geranium ‘Ann Folkard’: This is one of the earliest blooming geraniums with magenta flowers that repeat bloom throughout the season. This hybrid has a trailing habit and grows 6 to 8 inches tall in zones 5 to 9.Geranium ‘Double Jewel’: Double-white petals feature a lilac center. It’s short and sometimes grown containers, as it grows 10 inches tall. It is hardy in zones 4 to 8.Geranium ‘Southcombe Double’: Double, pure pink blooms resemble fluffy asters. It grows 10 inches tall in zones 4 to 8.
Pruning
Hardy geraniums require little care, once established. The plants can get a bit scraggly after blooming and deadheading is difficult with so many wispy stems. Shearing the plants back to basal growth will improve their look and encourage reblooming. The plants fill back in within weeks. The exception is Geranium macrorrhizum, which is easily deadheaded and needs no shearing.
Propagating Hardy Geraniums
Most species of hardy geranium live longer if divided every three to five years, though you can divide more frequently to keep them from spreading or to obtain new plants. Once you see the center dying out, it is definitely time to divide. Divide the geraniums in the early spring to early summer, giving the plant time to establish its roots before a frost. Here’s how:
How to Grow Hardy Geraniums From Seed
Many hardy geraniums will self-seed very readily, even taking root in sidewalk cracks. They do not spread uncontrollably, though, so they are rarely a problem in the garden. The volunteer seedlings can be easily dug up and transplanted elsewhere. You can also collect seeds and plant them wherever you like in the garden, or in seed-starter trays. They are relatively slow-growing plants, though, and when started from seeds it can take as much as three to five years before they are mature enough to flower. Be aware that hybrids and many cultivars do not “come true” from collected seeds; these must be propagated by root division or other vegetative methods.
Potting and Repotting Hardy Geraniums
Unlike the popular zonal geraniums (Pelargonium), hardy geraniums are perennial plants that are rarely grown in containers. That said, there’s no reason you can’t do it. Use a somewhat oversized pot that will give the plant plenty of space to grow, and fill it with any standard commercial potting mix. The container can be made of any material, but it’s crucial that it have good drainage. Fan out the roots of the geranium as you plant it. Hardy geraniums don’t like waterlogged soil, so weekly watering should suffice. They are relatively slow-growing plants, so repotting is required only when roots begin to poke out the drainage holes—this may take as much as three years. In colder climates, move the pots to a sheltered spot for the winter to protect the roots. These plants are not suitable for moving indoors to grow as houseplants.
Overwintering
Hardy geraniums generally require no winter protection against cold, but it is good practice to cut off the stems to just above ground level and discard the debris as winter approaches to eliminate fungal spores that can often cause powdery mildew.
Common Pests & Plant Diseases
Hardy geraniums are relatively trouble-free plants. Slugs may attack young geranium plants, while mildew and rust can infest foliage, especially in partial shade and/or humid climates. Shearing back and disposing of the infected leaves will help. To avoid mildew, give the plants plenty of space to improve air circulation, and water through ground soaking rather than overhead spraying. Mildew spores are spread from water splashing against the soil.
How to Get Hardy Geranium to Bloom
The bloom period for hardy geraniums varies somewhat depending on species, but generally you can expect them to bloom from early summer to early fall. Often there is one particularly heavy flush of flowers, with smaller blooms continuing in subsequent months. Shearing back plants after the main flush often stimulates more blooms to follow. When hardy geraniums fail to bloom as you expect, it’s usually for one of these reasons:
Too much moisture: Most hardy geraniums like fairly dry conditions, and if they are overwatered, they will withhold blooms.Not enough sun: These plants typically want at least six hours of sun daily, and if they don’t get it, flowering will be more sparse. The foliage itself, though, is often appealing enough to warrant growing the plant even in relatively shady conditions.Too much fertilizer: These plants thrive on little to no fertilizer, and if fed too often, the result can be excessive foliage at the expense of flowers. Fertilizers heavy in nitrogen are especially problematic.
Common Problems With Hardy Geranium
Some gardeners are surprised by the degree to which hardy geraniums can spread in the garden. Sometimes this is a pleasant surprise, as hardy geraniums can form a pleasing ground cover that weaves among other plants to block weeds. Other gardeners find it somewhat invasive. Fortunately, hardy geranium is relatively easy to dig out and eliminate if this habit is not to your liking. After flowering, hardy geraniums can become somewhat leggy and sparse. It’s an easy matter to cut back the sparse stems, which will stimulate new growth.
