Autumn-flowering gentians

Gentians are probably the most iconic and well-loved alpine plants to gardeners. Even those who neither have a rock garden, or aspire to own one, will wax lyrical on seeing the intense blue, upturned bells of a trumpet gentian. The experience may well bring back happy memories of rambles in the European mountains. Here gentians may often be found in their thousands, studding the alpine meadows with their awe inspiring blooms unlike any others.

Most of the gentians you may see in gardens, or for sale in garden centres, will be spring flowering. Either trumpet types or the equally beautiful ‘star’ gentians. They are easy plants to grow, but not always to flower well. But unbeknown to many gardeners are the many fabulous species from further east, notably the Himalaya, that flower chiefly in autumn. Not to mention the many wonderful hybrids, which are generally easier to grow than the species. Your best bet if you want to try some, is to visit an alpine nursery that specialises in these plants in the autumn and make your choice. Or, equally worthwhile, visit an AGS autumn Show, of which there are several in different parts of England. There you will see a range of varieties on the show benches and nursery stands.

Placement and planting

Unlike their spring-flowering cousins, most autumn-flowering gentians are intolerant of lime in the soil. So special measures must be adopted to grow them in these situations. This may not mean just making special beds for them, or growing them in containers, but using rainwater where the tap water is alkaline. And a plentiful supply of water is needed as autumn-flowering gentians generally require soil that never dries out. A rich compost with plenty of well rotted organic matter suits them well, providing it is not prone to waterlogging.

Although they need humusy,  moist soil to flourish, they are mainly meadow plants that flower best in full sun. Light shade between shrubs may be satisfactory in climates that are sunnier than mine in North Wales.

If, for reasons of unsuitable soil, you need to grow your autumn-flowering gentians in containers, then troughs or other similar receptacles are satisfactory in the open garden. Or you can grow them in plastic or terracotta pots or pans. I prefer plastic containers in this instance because the compost is less likely to dry out. I keep my potted autumn gentians out of direct sunlight, especially in the height of summer, by placing them on the north side of my alpine house. Once they are growing strongly in spring I give them an occasional liquid feed with a balanced fertiliser. The developing flowers are prone to attack by slugs and snails, which must be controlled.

The best times to plant autumn gentians in the open ground are spring or (preferably, in my view) early autumn, before they flower but are in full, vigorous growth.  Providing the soil has been well prepared no further action is required.

Propagation

You can increase gentian species from seed, but division is far faster and easier. The clumps of the Asiatic species and their hybrids form of a mass of so-called ‘thongs’. These are groups of a few leaf rosettes arising from thong-like roots. If you dig up a clump you can easily separate them into pieces with the fingers. Replant in fresh soil immediately. Water well, and they will grow away without a check. It is advisable to lift and divide clumps every 2-3 years. This ensures plants will retain vigour and continue to flower well.

Companion plants

The best companion plants for autumn-flowering gentians are bulbs, such as autumn-flowering crocuses, and particularly hardy cyclamen (see my companion articles). The colour palette of cyclamen in particular, from white through all shades of pink to dark magenta, goes especially well with the piercing blues of the gentians. But it is necessary to ensure that the soil  is neither too humus-rich for the cyclamen, nor too sharply drained for the gentians. This may require trial and error in your garden to get it just right.

Gentiana asclepiadea

Unlike most autumn-flowering gentians, European G. asclepiadea is a woodland perennial that flowers from late summer into autumn. Thus it grows and flowers really well in shade. This is the so-called ‘Willow gentian’, on account of its arching, willowy sprays covered in clusters of blue, sometimes white flowers.

Gentiana paradoxa x septemfida

You may be offered G. paradoxa in catalogues. However, that scarce and local Caucasian endemic is rare in cultivation. What you are actually likely to obtain is its hybrid with closely related G. septemfida. its geographical and taxonomic close relative, As is often the case with hybrids, this is more vigorous and easy to cultivate than either parent. The hybrid also has the priceless advantage of being tolerant of lime in the soil. For this reason alone, in my view it should be called ‘everyman’s’ gentian. It is easy and very long-lived in almost any soil and situation in the garden, except parched soil beneath trees.

Gentiana paradoxa x septemfida is a clump forming plant which puts up a ‘forest’ of twiggy stems in July. As summer moves towards autumn, clusters of buds form at the tips which open up to become startlingly blue mini posies – a truly gorgeous sight. The flower clusters last for a month or more. Once flowering is finished and the shoots have started to die back you can cut them back to ground level. If you want new plants, dig up a clump when the new shoots are just beginning to appear and split it into pieces, each with several ‘eyes’ and a decent amount of roots. Pot them up in a humus-rich but well drained soil and shade until they are growing away strongly. The divisions may well flower the following autumn, if not then the following year.

Gentiana septemfida subsp. lagodechiana

This is one of the best forms of G. septemfida, one of the parents of the hybrid just described. It is often called the ‘summer gentian’, it blooms earlier than the hybrid, in July and August. It is a good, easy gentian with broader, more imposing foliage and equally good flowers. Why not try both!