Hardy Geraniums are one of most versatile an adaptable perennials for our area. Available in many colors and habits, they can be useful in sun and shade, moist and dry, as a single specimen, as companion plants and as ground covers. These are not to be confused with the Pelargoniums which are the house plant, container and bedding plant “geraniums” which are not hardy outdoor plants in Colorado. The name “geranium” is derived from a Greek word meaning little crane, hens the common name “cranesbill” which refers to the appearance of the seed heads. The majority of the species of geraniums are native to the northern and mountain regions of Eurasia and North and South America although some are found in South Africa, India, Indonesia etc. Most grow in grasslands, meadows, roadsides and open woodlands. Therefore the natural habitat for most hardy geraniums seems to be sunny and moist or part-shade and moist or dry.
Most geraniums are tolerant of clay or light soils but many appreciate organic matter, and some from alpine areas like G. cinereum like loose soils. Although generally tolerant of pH variations, the more alkaline tolerant are said to be G. pratense and G. sanguineum. The flowers are five-petalled, usually in pinks, purples or white; many having contrasting veins, occasionally with a dark eye. The leaves also are attractive, some with rich red fall color and some with very pleasing fragrance when rubbed.
I am successfully growing many hardy geraniums in my North Boulder xeriscape although I know many would be happier with a little more water and/or shade.
Geranium robertianum is one of the oldest geraniums in cultivation because of its herbal values which were said to be many. It has exquisite filigree foliage which turns mahogany red in fall. Tiny white flowers bloom in spring on wiry branched stems. While it is said to be short-lived, it has never left my garden because it self-seeds so vigorously. Rock gardeners would do well to pass on this one while cottage gardeners would love it. It grows 3”-6” high and wider and probably bigger with regular watering.
Geranium pratense is one of the larger hardy geraniums growing 16”-24” in my garden but to 3’ with richer soil and ample moisture. I have the blue form, a white one and a wonderful blue and white striated one (G. pratense striatum) which Thompson and Morgan has unkindly named ‘Splish-Splash’ and which I prefer to call Geranium ‘Harlequin’. It is very tough and durable for me growing in dry part shade and in dry sun. I cut off 3/4 of the seeds after its spring bloom to conserve its strength and to allow it to reseed some.
Geranium cinereum ‘Ballerina’ looks fragile with its 6” high by 12” wide rosette and sweet lilac-pink flowers with purplish veining, but it is not a wimp. It is herbaceous, dying to the ground in winter but performs beautifully and blooms every spring and again if I dead-head it. G. cinereum subcaulescens is soundly evergreen and has what I call gorgeous deep purplish red flowers with black centers. Others have claimed it is a vulgar color dangerously close to magenta, but most guests to its show in my garden are disappointed that I seldom have it for sale.
G. macrorrhizum is a geranium that is also known as an herb, once important in perfumery. It has sticky and aromatic foliage, blooming May/June and sometimes again later with pink or purplish flowers. It can grow in sun or shade, moist or dry up to 12”-15” high and spreading. Geranium dalmaticum has fragrant, low-growing leaves 4”-6” high; it is a rhizomatous, carpeting plant with soft pink flowers in late spring. It is good in sun or shade and can tolerate drought. It turns red in fall. Geranium x cantabrigiense is a cross between G.macrorrhizum and G. dalmaticum. It is one of the toughest and most drought-resistant geraniums in my xeriscape, growing 6”-12” tall (3”-6” dry) and spreading to form a ground cover that does well under trees where grass doesn’t do well. The flowers are pink, blooming in late spring. There is a natural selection ‘Biokovo’ with pale pink flowers that is perhaps a little shorter, longer blooming and more spreading. Both are excellent ground covers with fragrant leaves that turn red in fall and will grow to 8500’.
Geranium x magnificum has rich violet, dark-veined flowers in mid summer. It grows to 2’ and is tolerant of various soils.
Geranium sanguineum has blood red foliage in the fall and is drought and alkaline tolerant. Other than that the forms are quite variable: some have pale purple flowers, others are vibrant magenta. Said to be 12”-18” high but can be 6” and I have one that grows to 2’ before collapsing under a heavy rain or strong wind. It is very floriferous and long-blooming. There are many cultivars: ‘Album’ is pure white, weed inhibiting and as tough as it is beautiful; var. striatum (aka lancastriense) is a smaller variety with flesh-pink flowers with attractive veining; and there are many others.
G. ‘Johnson’s Blue’ has very beautiful deep blue flowers in June/July on a tough, sprawling plant 18”-24”. I have seen this one naturalize in rather difficult conditions.
G. renardii – this variety has remarkable textured, sage-green/gray foliage to 12”-18” with white flowers with purple veining. The form is not floppy and is very attractive the entire season. It prefers more moisture.
Of the native Colorado geraniums, I am growing two: G. fremontii has clear pink flowers with attractive veining, not dramatic but lovely. This plant grows 12” tall and 2’+ wide with floppy stems, and is the longest blooming plant in my garden, flowering from mid spring through October. It has large fleshy roots which aid in its drought tolerance. My G. richardsonii has only been in the ground a year and a half, but already I really enjoy the elegant pure white flowers where it grows in part shade. I am not growing G. viscosissimum, the Sticky Geranium, but I don’t know why. It is very showy with pink to purple flowers and often dramatic veining. I see it frequently on wildflower walks and it is obviously tough and drought tolerant.
Have I described every geranium I could think of? Not at all. Fortunately there are many more that are successful here. And I have only hinted at the wide range of uses possible. Plant them near roses, put them in that impossible spot where it is shaded all day and roasted by the late afternoon sun; put them in rock gardens, herb gardens, cottage gardens, xeriscape gardens and moon gardens. Get to know the hardy geraniums; they’ll show off your green thumb.