Geranium tuberosum

Geranium tuberosum, is one of the few species of perennial geraniums with tubers. This botanical species from the Mediterranean is rarely available in horticultural trade. Its foliage, very finely cut, remains evergreen in mild climates, emerges in spring elsewhere, and is adorned with a cloud-like mass of small cup-shaped flowers in a slightly mauve pink, with purple-violet veins. This geranium goes dormant in summer after flowering. Plant it in autumn, in well-drained soil, in full sun, in the rockery, in a border, or even at the base of a hedge. It will thrive and naturalize quickly in sufficiently dry soil in summer.

Among the large family of geraniaceae, there are perennial botanical geraniums particularly adapted to the Mediterranean climate, but generally resistant to heavy frost in well-draining soil. These plants have a growth cycle similar to that of autumn bulbs, such as crocuses, daffodils, and tulips. Their growth sometimes starts in autumn and persists throughout winter depending on the climate, allowing them to flower early in spring and disappear in summer, persisting as underground tubers to escape heat and drought. This allows them to be cultivated in a manner similar to tulips in humid and moist climates, by digging up the tubers in July and storing them dry until autumn.

Geranium tuberosum is one of them, native to Mediterranean Europe, western Asia, and North Africa. This tuberous geranium develops very finely cut foliage, whose structure somewhat resembles that of ice crystals. It forms a mound 20-25cm (8-10in) tall. The clump expands over time through the multiplication of its tubers. When it is happy, this plant can become somewhat invasive. The flowering, quite brief, takes place from April to June, depending on the climate. Above the foliage, reddish pubescent peduncles rise, branching at their ends. They bear flat cup-shaped flowers with a colour that is intermediate between pink and mauve. Each petal is veined with purple-violet, and the centre of the flower is often more pink. This flowering is followed by the formation of characteristic crane's beak fruits, typical of geraniums. The vegetation disappears after flowering.

The tuberous geranium, like most Mediterranean bulbous and tuberous plants, thrives in highly-drained limestone soils. However, any well-drained ordinary soil is suitable, even neutral or slightly acidic. It will naturally find its place in a rockery, on a slope, in a gravel bed, or as a border along a path, especially in a dry garden. It can also be placed at the base of an evergreen hedge, on the sunny side of course, as their roots dry out the soil in summer. Note that this plant is perfectly hardy and thrives very well in alpine greenhouses. It can be combined, for example, with pulsatilla anemone, Callirhoe involucrata or mountain cornflower. A sowing of nigellas and California poppies will also accompany it on a dry slope.