Growing the Perennial Geranium
Our hardy perennial geranium plants, referred to from here on as simply Geraniums (we'll forget pelargoniums ever existed) are wonderful plants occupying a wide range of garden habitats and providing a good range of colours for the enthusiastic gardener.
How to Grow
In general, the perennial geranium prefers a good soil, well drained (there's one exception to this rule!) with little or no drying out between waterings.
Moderated fertility is the rule of thumb - excess nitrogen simply produces tons of foliage at the expense of the flowering. The perennial geranium is a plant of the mixed border, with heights ranging from the ground hugging G. cinereum at 10-15cm (4-6") to G. psilostemon that rockets up to 120 cm (3-4 feet).
Growing wonderfully in mixed shade - a bit of midday sun protection keeps the perennial geranium leaves from getting too straggly, they do survive in full sun (with good watering) as well as a heavier shade (with perhaps a reduced flowering). Think of it as a plant of the forest edge or clearing, doing best on half day sun, rich organic soils, and regular supplies of moisture.
Flower Colors
The perennial geranium flower colours tend to the blue and pink tones. Even the reddish flowers are heavily toned with blue. With the more vigorous of plants, after the May-June bloom is finished, a light shearing will bring on a second flush of bloom later in the fall. If this technique is to be used, the soil should be well composted to allow for the extra flush of growth and energy needed for flowering.
Plants to Watch For
G. x cantabrigiense 'Biokovo'; I have to start off with the biggest disappointment for me in the entire class of perennial geranium. This plant was touted a few years ago as being one of the best new introductions of the millennium. Pale washed out whitish flowers on a non-descript foliage earned its neglected status out in the nursery. Unless I obtained the wrong plant, this perennial geranium is not worth pursuing.
G. cinereum; This is a wonderful short little perennial geranium plant, 4-6 inches tall which tends to form more of a rosette in its leave habit than other more sprawling species. The species does range in colour from a pale white to a bright magenta pink. The form I have is one of the brighter pinks and is quite a delight in May and June when it blooms.
G. clarkei; There are several perennial geranium cultivars available in this 18-24 inch tall form with a creeping habit. 'Kashmir Purple' or 'Kashmir Blue' are the most common although there is a 'Kasmir Pink' out there as well. The foliage on the G. clarkei is a finer cut foliage than many of the other geraniums and this alone gives it garden space.
G. endressii; The most common cultivar of this perennial geranium species is 'Wargrave Pink' with its very vigorous growth habit and salmon pink flowers. 18-24 inches tall, this plant is an excellent border plant and should be on every gardener's hit list for geranium culture.
G. himalayense; There are many varieties of this perennial geranium on the market and most are quite good. 'Gravetye' is an excellent creeping form with good blue flowers. 'Birch Double' is another good deep blue with double flower that is worth a place in any garden (I have to move mine to a more favourable spot) although the double flowering form is less vigorous than any of the singles.
G. macrorrhizum; This is an extremely hardy perennial geranium with scented foliage - a truly unkillable plant. I've grown the species and a few cultivars, eg. 'Bevan's Variety' with its deep magenta blooms, and I've liked them all. They are fairly vigorous and can act as a medium fast spreading ground cover.
G. X oxonianum; This hybrid perennial geranium grows to 24 inches and has been less than a hit in my garden. In fact, the variety I grew, 'Claridge Druce' died on me. I'll try it again but for now the report card is still out on this form.
G. phaeum; This is a tall form, up to 24-30 inches in height with a dark, chocolate maroon flower. Interesting form and easy to grow, it would be perfect in the middle of a border if allowed the room to spread.
G. platypetalum; This species rises up to 18 inches and is a thick foliaged form, excellent for ground cover use. The flowers are a deeper violet and the foliage is a good thick leaf with more rounded form than other geraniums.
G. pretense; This Asian species has been hybridized quite heavily giving us some excellent varieties. Grown as all the geraniums, forms tend to be taller - ranging from 18 to 36 inches in height. 'Blue Chip' is a good blue form, 'Mrs. Kendall Clark' is a light violet blue and quite good. 'Silver Queen' if you can find it is one of the taller forms with a mature height of 36 inches and white flowers with a touch of pale violet in them. 'Wisley Blue' is another form that is available and at 24 inches tall with abundant blue flowers is one to be grown.
G. psilostemon; One of my favourite geraniums, this one does very well if grown in a moist soil beside a pond. Native to N.E. Turkey its magenta flowers with dark centres shriek out over the garden when it comes to bloom. The only downside to this plant is that its finely cut leaves resemble many garden weeds leading to premature weeding in the spring. A variety 'Bressingham Flair' is shorter and without the magenta cast to the flower - it is almost a pink instead (and not so nice as the species)
G. renardii; I've grown this species for a few years now and it has a very small pale violet flower with streaked purple veins in the blossom. I've been growing it in the wrong position (full sun) and will be moving it into the semi shade this fall where I expect it to do much better. Native to the Caucasus mountains and quite hardy.
G. sanguineum; There are many varieties of this popular species on the perennial market. A spreading form with good ground cover characteristics, the varieties tend to be in the 18" tall range. 'Splendens' is a pale pink with violet tones and is 24 inches tall, 'Shepherd's Warning' is a compact growing form with bright violet pink blossoms. There are almost too many varieties to name in a short article (an article all by themselves)
G. sylvanicum; This is a more upright form of geranium rather than the sprawling ground cover forms and it grows to 30 inches or so. Varieties include: 'Album' a white, 'Birch Lilac' a violet lilac shade, 'Mayflower' a more intense violet blue, and 'Silva' a pale blue.
G. thunbergii; Watch out for this one. It has very small white flowers and an expansive habit that more resembles Ghengis Khan than any other geranium I've ever grown. From one tiny plant - it grew to conquer a nation! A great ground cover for waste spaces but almost impossible to control. I've given up and letting it run wild in its own corner far from the real garden.
G. wallichianum; This Afghanistan native is slightly shorter than other forms and a touch more tender. 'Buxton's Variety' is the most commonly available variety and its dense growth habit and pale China blue flowers are worth a place in most gardens.
There are other forms on the market that are hybrids and don't follow an easy classification. 'Johnson's Blue' is the most popular of these, being a cross between G. himalayense and G. pratense. An excellent blue colouring and dense growth habit makes this a good plant for border or ground cover.
Hybrids
There are a growing number of hybrid geraniums on the market, the most popular and deservedly so is 'Rozanne'. This plant blooms most of the summer and is as hardy as they come. A Perennial of the Year - it should be in every garden.
To sum up, the true and hardy geranium family is an excellent plant that can find a place in the perennial border, pond side, shadier garden, ground cover - just about any place that you have to fill. If you don't have some of these - it won't be from me not bringing them to your attention.
Clck here to ask about growing the perennial geranium.
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