How to grow autumn gentians

When most people think of gentians, they envision the bright-blue flowers that bloom in the Alps during spring. But there is another gang of gentians, which looks similar, but hails from Asia and flowers now, in autumn. The best garden forms of these autumn gentians are Gentiana sino-ornata and its hybrids. A low-growing semi-evergreen perennial from Tibet and China, G. sino-ornata produces 6-centimetre long electric-blue trumpets from September to November, and it has parented many of the good autumn-flowering varieties, which range in colour from pale baby blue to rich, glossy indigo.

Plant collectors of the early 20th century became quite obsessed with Asiatic gentians, which isn't surprising, since the piercing-blue flowers make them stick out, jewel-like, on the scrubby slopes and pastures of the Himalayas. Scottish botanist George Forrest found Gentiana sino-ornata in Yunnan, and, when it bloomed for the first time in Britain – in the Royal Botanic Garden Edinburgh – people flocked to see it. Enjoy these blue beauties in your own garden by giving them the moist, free-draining conditions they love, in which they are very well behaved.

Which autumn gentians to grow

There is a wide range of hybrids, which are often the offspring of the showy Chinese gentian (Gentiana sino-ornata), in every shade of blue. Growing a range of blue hues gives a great effect en masse. 'Strathmore' is a pale sky-blue form; 'Blauer Kobold', 'Braemar', and 'The Caley' are mid-blue shades of ultramarine; while 'Faszination' and 'Sensation' are deep lapis blue.

How to plant autumn gentians

Choose a sunny site that has retentive, well-drained soil. Fork in leafmould or compost to boost retention and drainage, if necessary. Since they are low-growing plants that you'll want to look closely at, and because they grow in an expanding mat, they are best at the edge of borders, perhaps dressed with gravel, since this conserves moisture, wards off slugs, and looks good.

Neutral to acid soil is essential; Gentiana sino-ornata and its hybrids loathe lime, so if your soil is alkaline, plant them in a container with ericaceous compost. The lax stems grow in a spreading prostrate fashion, so autumn gentians look great in stone troughs, which can often be found in reclamation yards.

How to grow autumn gentians

In its preferred conditions, Gentiana sino-ornata is a doddle to grow.

Drainage and moisture: autumn-flowering gentians enjoy free-draining, moist soil because their natural habitat is the damp mountain meadows and open forest and scrub of the Himalayas, where the annual snow melt runs around their roots.

Sun: in the wild, autumn gentians grow in full sun, but their feet are always damp. So, if you live in a region with good rainfall (such as Dartmoor or Scotland), a south-facing open sunny position is great; otherwise, plant in a west-facing spot, ensuring that the earth is retentive during summer. In a garden that suffers from drought, a waterside spot or a site is semi-shade is preferable.

Acid soil: G. sino-ornata turns its nose up at lime, so a neutral to acid soil is vital. If watering gentians in containers, never use hard water from the tap; either filter it and add a drop of vinegar (to alter the pH) or use rainwater.

Food: mulch with compost or well-rotted leafmould each spring. You could also give them a dash of blood, fish, and bone.

Propogating: sometimes the prostrate rooting stems make new plants ('thongs') by themselves. But to keep the gentians floriferous and make new plants, lift and divide every 2 to 4 years in early spring. Dig them up with a fork and gently prize them apart into smaller sections, before replanting.

Pests: if slugs and snails are a problem in your garden, dress the plants with gravel.

Foliage: G. sino-ornata is semi-evergreen. During winter, don't be alarmed if parts of the plant looks brown or orange. This is the annual process of the leaves and stems dying back to a central rosette.

Spring-flowering gentians

The bell gentian (or stemless gentian), Gentiana acaulis, hails from the Alps, where it dots the mountainsides with patches of sapphire in April and May. One of the easiest spring gentians to cultivate (if it likes you), it is also the most widely available. It forms a clump of evergreen leaves that are topped with vivid-blue trumpets. 'Rannoch' (deep cobalt) and 'Krum Rey' (electric blue with a green throat) are two good hybrids.

In general, this spring form won't bloom as abundantly as the autumnal G. sino-ornata, but the flowers tend to be larger. Like its autumn cousins, it loves very well-drained, moist soil, in part shade or sun. Some of the standard advice is not to plant G. acaulis in alkaline earth, but many gardeners report success on limey soils.