SINCE early this year 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. I would sink a pot containing a plant that was looking its best into the ground – known as plunging – however as we head towards autumn, the choice of plants to display becomes a little thin so the arrival of the autumn gentians is welcome.

Gentians, along with Edelweiss, are the symbols of the alpine world. 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 more than 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. However, each species requires slightly different conditions: some lime tolerant, some lime loving, some lime hating, and if you do not know exactly which type you have of a similar looking gentian, it can mean shortlived 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 they’re 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, although requiring free-draining soil, like it moister and with some light shade, so are more suited to a border.

Finally, the autumn flowering gentians.

Their origins are in the Himalayas, although some are Japanese, and they have the brilliant electric blue trumpets. Many are stripped with white markings on their bells adding even greater contrast. The great plant hunters of the Victorian era brought these treasures back from China.

They were found on the northern border with the Himalayas growing at high altitude or in mountain pastures.

In 1914, Reginald Farrer discovered, Gentiana sino ornata, the Chinese autumn flowering gentian. This gentian is well known as it is from this plant the enormous varieties of hybrids have been produced over the years, nursery men painstakingly cross-pollinating with other species of gentians to create these beautiful differently varied plants. They grow vigorously and bear an enormous profusion of flowers in colours of pure deep blue and also white.

Autumn flowering gentians can easily be grown in the garden and require a cool spot with some sun to open their bells. They need a well-draining soil, preferably slightly acidic and enriched with leaf mould.

At Harlow Carr, they can be found at the edge of the woodland in the garden on the Peat Terrace, their electric blue bouncing out of the shade and, of course, on display in the Alpine house for the coming months.

Harlow Carr diary dates

PHOTOGRAPHY MORNINGS
Saturdays in September from 8am
Make an early start and take advantage of the early morning light to capture the beauty of the late summer garden

WILLOW SCULPTURE TRAIL
September
Come and see a selection of new willow sculptures in the garden as part of this month-long trail

MOSAIC EXHIBITION
September 10-21

Large variety of work on display from the British Association for Modern Mosaic.

  • Events at RHS Garden Harlow Carr are free with the normal garden entrance fee, except where stated. For further information call 01423-565418.
  • RHS Garden Harlow Carr, Crag Lane, Beckwithshaw, Harrogate HG3 1QB (Sat Nave postcode HG3 1UE). Open daily from 9.30am until 6pm (4pm Nov to Feb). RHS Members free, adults £7.70 (or £8.50 including gift aid), children (five to 16) £3.85 (or £4.25 including gift aid), under-fives free. Gardens: 01423-565418; shop and plant centre: 01423-724666; Bettys tea rooms 01423- 505604.

TO DO THIS WEEK

  • Keep deadheading late flowering plants such as salvias and dahlias to encourage new flowers.
  • Plant or relocate shrubs while there is some warmth still in the soil.
  • Divide herbaceous perennials, but replant immediately.
  • Tidy borders, cutting back untidy plants and removing debris to discourage pest and diseases.
  • If you have been using nematodes for vine weevils it is a good time for the last application before winter.