Dahlias are coming back into fashion. They were popular in the 1950s and 60s and were often seen growing in rows as collections in allotments and front gardens. Somehow, though, they slowly fell from favour.

They began to be labelled as old-fashioned. Maybe this was because they require more attention than other plants, and at a time when our lives were becoming increasingly busy, plants like dahlias became considered too fiddly and time-consuming. Now, however, the intricacies of looking after dahlias seem to be part of their attraction again – dahlia therapy, if you like.

Dahlias with dark foliage, particularly those belonging to the ‘Bishop’ series, are among the most popular. Bright flowers, lingering late into the season and glowing against almost black leaves, have caught the imagination.

It is said that the first dahlia with very dark foliage to be introduced to commerce was known as ‘Lucifer’ and was bred in France. Breeders then realised the potential of dark foliage and set about raising dahlias with a combination of dark leaves and shapely, colourful blooms.

In 1927, a dark red dahlia with purple-black foliage was produced in Wales and named Dahlia ‘Bishop Hughes’. Unfortunately, the said bishop was not at all happy with his name being applied to a variety of dahlia, so the dahlia was then renamed ‘The Bishop’.

However, one of the rules of botanical nomenclature for dahlias at that time stated that the use of ‘The’ was not allowed as part of a name. As a result, the name of the red-flowered variety with dark foliage was changed to ‘Bishop of Llandaff’ – the name by which it continues to be known today.

There is now a whole collection of ‘Bishop’ dahlias, all characterised by dark foliage. Flower colours vary and include shades of lemon, orange, red, pink and purple.

At the moment, dahlias are in full bloom. They will continue to flower until the first frosts of autumn, when their foliage will wilt and soften overnight in the cold. After this, it will be time to cut back their growth and lift the tubers from the soil so they are never exposed to frosty conditions.

Tubers that have been frosted turn to mush within their outer casing. I usually wash most of the soil away from freshly lifted tubers with the hose – the less soil that is left around the tubers, the faster they will dry and the less prone they should be to rotting while in storage.

They need to be stored for winter in a dark, cool, frost-free and mouse-free place. Some gardeners store them the right way up in boxes of barely damp compost, but I prefer to adhere to the method we used when I worked as a teenager in a market garden – upside down on a cellar floor and covered in layers of sacks.

They will be ready to come out of storage in March when they can be potted up and started into growth again beneath the protective glass of a cold frame.

Growth is lush and soft, and it is at this time that cuttings of can be taken of favourite varieties. After the last frost, dahlias can be planted out in late May or early June, ready to begin a new season’s display of foliage and flowers.