Quite simply, something is clearly missing if you don’t have at least one species of Gentian in your rockery. The blue trumpets of this alpine plant can provide colour from May to September if you grow spring-, summer- and autumn-flowering types. With Gentians you should always look up the likes and dislikes of a particular species before you buy it – one Gentian’s meat is another Gentian’s poison. Lime is the problem – spring-flowering species either tolerate it or require it, but the autumn-flowering Gentians cannot tolerate it. All of them demand free-draining but not im-poverished soil. Add peat and some grit to the soil before planting – most Gentians are rather temperamental and cannot be regarded as ‘grow anywhere’ plants.

VARIETIES: The easiest one to grow is G. septemfida which will give a good display of 1 in. long trumpets in any well-drained soil. Its basic details are height 9 in., spread 1 ft.

Flowering period: July-August. The popular G. acaulis (Trumpet Gentian) is a smaller plant (3 in. high) and blooms earlier (May-June), but its flowers are much more eye-catching – 3 in. long trumpets standing upright above the glossy oval leaves. Unfortunately it is unpredictable – in some situations it will not bloom and nobody knows why. If your plants are flower-shy, simply move them to another spot in autumn. G. verna is another spring-flowering Gentian – height 3 in, spread 6 in.

Flowering period: May-June. Its star-like flowers are bright blue and borne singly rather than in clusters. An attractive evergreen, but unfortunately the plants are short-lived. The most popular autumn-flowering Gentian is G. sino-ornata – height 6 in., spread 1 ft.

Flowering period: September-November. The 2 in. long trumpets are bright blue with pale green stripes – a showy display when little else is in flower in the rock garden. In order to maintain the vigour of this plant, divide the clumps every 3 years.

SITE AND SOIL: Well-drained soil is essential – lime should be present for spring-flowering types but the ground must be acid for the autumn-flowering ones. Thrives in sun or light shade.

PROPAGATION: Divide clumps in spring (autumn-flowering Gentians) or midsummer (spring-flowering Gentians). Propagation from seed is difficult.

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