Dahlias are a bit like Winston Churchill or John Travolta. They too have had wilderness years when nobody really understood them and they floundered about, failing to fulfil their full potential. As a child I remember them as rather vulgar flowers with heads the size of wombats, each one lashed to a sturdy bamboo in a sort of horticultural crucifixion. Their purpose was to be picked for over-the-top flower arrangements, or to be entered in local horticultural shows as prime examples of their breed. The shows would be like Crufts, where many of the champions have been so primped and combed that they look nothing at all like their domestic cousins who charge around with matted coats and muddy paws eating roadkill.

The exact reason for their cultural exile is a little unclear. They were included in a general clear-out of what was considered naff, alongside pampas grasses, patterned linoleum, drip-dry shirts and hybrid tea roses. Part of their disgrace may have been that they were considered too high-maintenance, as they are annuals (and likely to die if heavily frosted), and the whole kerfuffle of digging up and overwintering tubers was considered too much fuss. But the main problem was probably that they were considered overbred. This was a mistake: admittedly, some of the varieties are too over-the-top for a normal garden – for example some of the giant varieties, with flowers up to 30cm across – but there are so many others that to exclude them from our gardens was a crying shame.

Dahlias have not been around here for that long but have come a long way. The wild dahlia is an unassuming fellow. It has small starry flowers and scrambles about on scrubby Central American hillsides. In 1872 a box of dahlia tubers was sent from Mexico to the Netherlands: one survived, and so began the stream of hybrids we grow today.

Dahlias possess an interesting genetic tweak in that they are octoploids – they have eight chromosomes instead of the normal two. All this botany means that if you sow the seeds of any dahlia, there is absolutely no telling what will come up: could be pink, could be huge, could be yellow, could be anything. Most will be unremarkable but every so often a jewel surfaces, and it is from these experiments that the many hundreds of hybrid dahlias that are loose in the world have emerged.

The varieties range from knee-height to as tall as a large horse, while the flowers can be anything from delicate daisies and pom-poms to cactus-headed blooms that look like sea anemones. The late Christopher Lloyd was one of the first publicly to trumpet their advantages. For him it was mostly a matter of rebellion against the tasteful and refined world of the pastel-coloured border: “Faint-hearted gardeners cannot abide the way they flaunt their brilliant clean colours,” he said. Rather than growing them separately in

cutting gardens or at the back of greenhouses, Lloyd advocated assimilating them into the herbaceous border and using their myriad shapes and colours in association with other plants. They are admirably suited to this job, especially as the most convincing argument in favour of the dahlia is that it flowers so enthusiastically for such a very long time: from July until the first frosts.

The most respectable dahlia is D. ‘Bishop of Llandaff’: even when scorn was being poured upon the heads of its brothers and sisters it was allowed limited access to smart gardens. It is a remarkably fine plant, with shining red flowers and fern-like purply leaves. There are so many others that you should try: D. ‘Clair de Lune’ has the same shaped flower but in palest yellow, and represents a good second step for the cautious. For those prepared to embrace full-bosomed glory, try D. ‘Hillcrest Royal’ (another Christopher Lloyd favourite), a 1.5m-high Sputnik of vibrant purple, or D. ‘David Howard’ – orange with bronzy foliage. Sarah Raven (another champion of the dahlia) is very keen on a triumvirate of dark, moody plants – ‘Rip City’, ‘Chat Noir’ and ‘Bishop of Auckland’ – that add sex appeal to any border.

For those who prefer paler colours there are some spectacular whites such as D. ‘Oreti Bliss’ (a spiky cactus) or D. ‘L’Ancresse’ (a tight ball of rolled petals). Pinks are also available: D. ‘Aitara Caress’ is the colour of seaside coconut ice and goes well with blues. Do not forget the less pushy varieties, especially D. merckii, which is the closest we get to the native dahlia (and probably the hardiest we grow): single lilac flowers on rangy stems that clamber over surrounding plants.

A word of warning: although most members of the family are extremely personable, some of the varieties are revolting. Steer clear of anything the colour of raspberry ripple (especially with a hint of yellow) and remember that the very large-headed varieties are still best left at the village show. As regards the complaint that they’re troublesome to grow: I have found that a thick mulch is enough protection to get them through the winter (especially in the soft south of the country) without lifting the tubers but, to be perfectly honest, it is not that much effort to dig them up and store them in a shed. (Pot them in March or early April.) Once planted (in sunshine), then occasional feeding, lots of water and frequent deadheading will keep them happy and, more importantly, keep them flowering. Like any plant (or, indeed, person), if you look after them then they will look after you.

Use them widely and use them well, especially in autumn borders. Nothing brings as much joy to a fading summer as the dahlia: they give pep to asters, succour to late salvias, vim to verbenas and re-assurance to grasses. Most importantly, it is almost impossible to look upon a dahlia without smiling.

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