There are numerous perennial species of hardy geranium, and many are reliable, long-flowering plants. Most Cranesbill geranium (not to be confused with tender, pot-plant pelargonium) are easy to grow. Cranesbill range from about 6 to 39 inches tall and work well planted in perennial borders as edging plants. Most have attractive, deeply divided leaves, and the flowers cover a range of shades, mostly in violet, blue, pink, rose, and cerise. Most like sunlight, but some others prefer shade. Perennial geranium plants need a well-drained location, but it doesn't need to be rich. The soil needs amending with lime before planting if acidity is high. Use a soil testing kit to ascertain the quantity required.