Since spring I have been looking after the Alpine House at RHS Garden Harlow Carr. In the spring months and into early summer looking after our display was easy, plunging the pots looking at their best, however as we head towards autumn the choice of plants to plunge becomes a little thin and the arrival of the Autumn Gentians brings a sigh of relief.
Gentians along with Edlweiss are the symbols of alpine flora and the alpine world itself, you only have to look at the symbol of the Alpine Garden society and you find Gentiana acaulis. This gentian is probably the image conjured when you think of the gentians, the deep electric blue of its giant trumpet. However, it is a large genus with over 400 species, hence their origins are throughout the world in many different habitats and growing conditions and thankfully those which bring autumn flowering interest.
Beginning with the spring flowering Gentians, these are usually of European origin, dark gentian blue in colour and usually evergreen. They are the big names in the Gentian world, Gentiana acaulis and Gentiana verna. Gentiana acaulis are the big trumpets commonly known as the Bell Gentians and apparently the ‘true’ Gentian blue lies deep within their bells. Many similar looking species are grouped together under this name by nurseries and often sold as “Gentiana acaulis”.
Gentiana verna are slightly lighter in colour and have much smaller bells but usually in multitude, these are commonly known as Spring Gentians. They both suit a rock garden environment with a moist but free draining soil in a sunny spot. If you like alpines it is likely these are the two you have bought, planted in your own garden and they have failed to establish. The problem with spring gentians is the medley of different forms sold by nurseries as the big blue trumpet gentian. Each species requires slightly different conditions, some lime tolerant, some lime loving, some lime hating and some requiring lime, if you do not know exactly which type you have of a very similar looking gentian it can mean short lived plants.
Thankfully for the rest of the year things get easier, summer flowering Gentians such as Gentiana septemfida and G. cruciata tend to be taller, their blue not quite as sharp but much easier to grow in a rock garden or trough. The Willow Gentian growing in late summer from August through to September has attractively drooping stems with clusters of flowers, not a blaze of colour, their pale blue often flushed with pink but an attractive flower. These requiring free draining soil and like it moist with light shade. Finally the Autumn flowering gentians, their origins in the Himalayas, they have the brilliant electric blue trumpets and can be found at the edge of woodland in the garden on The Peat Terrace, their electric blue bouncing out of the shade.