September flowers: what's really in season in Switzerland?

The aster has the strongest claim. The birth flower tradition, rooted in the English-speaking world and shaped by the Victorian language of flowers, gives September to the aster, with the morning glory as runner-up. Each morning glory bloom lasts a single day, opening at dawn and closing by the afternoon. The word aster comes from the Greek for star, a nod to its radiating flower heads. A Greek legend has the flowers springing from the tears of Astraea, the goddess of justice and starlight.

The choice is anything but random. In temperate climates asters peak in September and early October, just as most summer perennials are running out of steam.

And the lily? A few online florists present it as the star of the month, although no tradition ties it to September.

Dahlias, the backbone of late-summer bouquets

Dahlias come from Mexico, where the Aztecs called them acocoxochitl and ate the tubers. The dahlia was declared Mexico's national flower in 1963. Its name honours the Swedish botanist Anders Dahl, a student of Linnaeus. Linnaeus did not name it himself, though, since he had been dead for more than eleven years when the plant reached Europe.

In neighbouring France, a certain Dr Thibaud introduced it in 1802 as a substitute for the potato. The taste, rather like a bitter and stringy artichoke, soon settled the matter and the dahlia went back to ornamental gardens. Tens of thousands of varieties exist today, from tiny pompons to giant decoratives such as 'Café au Lait', a firm favourite with florists.

If you are cutting your own, one detail matters more than any other. A dahlia bud cut too early will never open in the vase. Choose flowers that are already open or just about to be, cut them in the morning and make the cut just above a leaf node to encourage new blooms. Most fields leave a knife at the entrance. Regulars still bring their own pocket knife, just in case.

Asters: check the label before you buy

What gets sold as an aster is not always an aster in the botanical sense. North American autumn asters such as the New York aster were moved to the genus Symphyotrichum after their DNA was compared with that of Eurasian asters. The China aster, meanwhile, is now Callistephus chinensis, an annual grown mainly for the cut-flower trade.

In Switzerland the distinction has legal consequences. Since 1 September 2024, the revised Release Ordinance has banned the sale, gifting and import of the New York aster group (Aster novi-belgii aggregate) because these plants escape into the wild and crowd out native species. Plants already growing in gardens are not affected.

There is no shortage of alternatives. The native Italian aster (Aster amellus, known locally as Berg-Aster) grows in the warmest and driest parts of the country and opens its pale violet flowers from August. It needs lean, free-draining and chalky soil, since it tends to flop in rich ground. More than 70 species of wild bee feed on it. For an ordinary border, Frikart's aster (Aster × frikartii) is more forgiving. This cross between the Italian aster and an Indian species was bred and popularised by a Swiss master gardener.

Japanese anemones, which actually come from China

The name is misleading. Anemone hupehensis is native to central China, in the province of Hubei. It owes its common name to its long history of cultivation in Japan, where it has been grown since the 17th century. The botanist Robert Fortune brought it back from China in 1844. In Chinese it goes by the name of broken bowl flower.

It is one of the few perennials that flowers happily in partial shade, from August until the first frosts, in successive waves over six to eight weeks. The white cultivar 'Honorine Jobert', discovered around 1858 in a garden in Lorraine, remains a classic for dappled corners.

Chrysanthemums, long before All Saints' Day

In Switzerland the chrysanthemum is closely linked to cemeteries. All Saints' Day on 1 November is a public holiday in the Catholic cantons, from Lucerne and Valais to Ticino. Many families decorate the graves of relatives with candles and flowers, usually chrysanthemums. In neighbouring France the custom took hold in 1919, when President Raymond Poincaré called on the French to lay flowers on soldiers' graves for the first anniversary of the Armistice. The chrysanthemum won out because it was plentiful in November and could stand the cold.

In Asia, by contrast, it symbolises longevity and Japan made it the emblem of its emperor. Florists have rediscovered small-flowered and more graphic varieties, which start appearing in their arrangements in September.

Alongside these classics, September gardens also have sedums in pink or purple, yellow and orange rudbeckias that draw in pollinators and the last sunflowers holding on into early autumn.

Autumn crocus: admire it, never pick it

Walk through damp meadows in September and you will spot pale mauve cups rising straight out of the grass without a single leaf. This is the autumn crocus (Colchicum autumnale, Herbstzeitlose in German, colchique in French), which flowers from August to early October. Every part of the plant contains colchicine and is extremely toxic, the flowers most of all. It has no place in a wildflower posy. The easiest way to tell it apart from true autumn-flowering crocuses is to count the stamens. The autumn crocus has six, crocuses only three.

Not every spring bulb needs to go in straight away. Snowdrops do not cope well with drying out, so plant them as soon as you get them home. Tulips and daffodils mostly go in during October. If the weather turns cool, the second half of September works too. By then the soil should be no warmer than 15 °C. If biodiversity matters to you, choose native species such as the spring crocus (Crocus vernus), the snowdrop (Galanthus nivalis) or the winter aconite (Eranthis hyemalis).

September is also a good time to plant perennials, while the soil still holds some summer warmth and the autumn rain returns. Italian asters, heucheras and ornamental grasses root over the winter and flower the following year. Water them in generously.

On the balcony, cyclamen, heathers and potted chrysanthemums keep the colour going into October, especially in a sheltered spot.