So echinaceas seem to have everything going for them. However, there is a “but”. Ask any group of gardeners to name a perennial that seems less than perennial, and echinaceas are nearly always there in the first five or so suspects. “Here one year, gone the next” is often the verdict. Why this is so is a bit of a mystery, especially since the plants look as though they ought to be fully perennial. Most true short-lived perennials have a distinct “neck” at the base of the plant where all the top growth joins the root system – there are no little shoots moving out with their own roots to make their way in the world. True perennials have these shoots from an early age. Echinaceas have them; it is possible to see, or feel, that at the base of the plant there is growth that wants to spread out and form a clump, albeit a tight one, as these plants do not spread freely. Next time you are at the garden centre, I suggest you try this – get your fingertips in at the base of some perennials in pots and see what you can feel.

Disappearing act

The best person to ask about echinaceas’ longevity has to be Neil Diboll, of Prairie Nursery, who has more than 30 years’ experience of growing prairie plants in Wisconsin. He tells me: “Echinacea purpurea is relatively short-lived, five to 10 years. Echinacea pallida and angustifolia, 10 to 20.” But five years is still an awful lot better than dying the first winter. So why do echinaceas often just disappear?

There is no question about their hardiness. Winters in their homeland, the American Midwest, reach well below -20C (-4F), the ground freezes down to a metre and the snow lies so deep that people lose their cars. So cold hardiness is clearly no problem. Many gardeners blame slugs and snails for mystery disappearances but, in fact, echinaceas are no more vulnerable than other perennials.

Cassian Schmidt, director of one of Europe’s leading perennial gardens, Hermannshof in Weinheim, Germany, told me: “They appear to be competition-intolerant; they grow well on their own, but suffer if other plants crowd them.”

“Rubbish,” says nurseryman Bob Brown, whose Cotswold Garden Flowers has one of the largest ranges of perennials in the country. “I grow my plants densely; they are E. purpurea Bressingham hybrids – a darker-than-normal strain – and, although I no longer have the 10 I originally planted, the survivors are in there, in their fourth year now, cheek by jowl with geraniums, hemerocallis and rudbeckia, all jostling for space.

“Part of the problem,” reckons Bob, “might be winter damp… a plant which habitually goes into a deep-freeze winter just goes dormant… warm and moist conditions encourage pathogens, so echinaceas might rot easily in our mild, wet winters.” This is as good an account as any, and helps explain why there is a definite correlation between the amount of yellow in the flower and the number of people mourning the loss of a plant the first spring after planting. The gene for the yellow flowered varieties of echinacea comes from E. paradoxa, a species from dry habitats. As is so often the case, the hybridist’s creation of new colours and forms comes at a cost – in this case, breeding in an Achilles heel in terms of long-term performance.

Making it work

So what are the best echinaceas to grow for longevity? “None of them,” snorts Bob. “If people want to grow them, they can grow them as annuals.” There are several easily obtained seed strains that do, in fact, flower the first year, offering most of the range in colour and form that is found in the named cultivars.

Billy Carruthers, of Edinburgh’s Binny Plants, is more positive: “We grow the straight Echinacea purpurea,” he says, rattling off a list of older varieties, all of them an improvement on the original species, but not sacrificing what staying power it has. He recommends ‘Rubinglow’; ‘Rubinstern’, which has ray florets held horizontally; and ‘Ruby Glow’, which has extra-big flowers, and is one of the few with an RHS Award of Garden Merit (itself an indicator that these are less than totally satisfactory garden plants). ‘Magnus’ is an older variety, again with bigger flowers than the species – it used to have an AGM, which is better than never having had one. A recent AGM winner is ‘Elton Knight’, bred by Anthony Brooks, the gardener at Elton Hall in Herefordshire – its multiple stems and long-flowering habit make for an exceptional performance.

Insider tips

At around 30-40in (80-100cm) in height, echinaceas are quite big plants. ‘Kim’s Knee High’ is useful in that it has lots of smaller flowers on a 25in (60cm)-high plant; ‘Kim’s Mop Head’ is similar in size, with white flowers. Kim Hawkes, who bred them, is a nurserywoman in North Carolina, and not one of those who Carruthers describes as: “getting it onto the market as quickly as you can, without trialling it first”.

Dutch breeder Marco van Noort subjects his plants to three winters before releasing them onto the market – a recommendation indeed! Among his plants is ‘Irresistible’, which has a central cone blown into a fluffy mass of tiny florets and salmon-toned outer ones.

‘Alba’ is a very pale green, almost white, old E. purpurea variety with a good record; the other day I was running a garden workshop and one of the students told me hers was seeding itself in her garden. Anthony Brooks, who holds the Plant Heritage national collection, also tells me they self-seed freely – perhaps having a wide gene pool encourages a higher rate of fertile seed being produced. Good news indeed, but rare; I suspect our autumns are too cold and soggy for the seed to ripen properly. Profuse self-seeding, by the way, is often a sign that a species is short-lived.

Other whites that Binny Carruthers rates are ‘Jade’ and ‘Green Edge’. One which Bob Brown says is “an improvement on many… because of the shapeliness of the plant”, is ‘Coconut Lime’, which has a rounded soft-textured cone.

The future will undoubtedly bring many more varieties. Most will be transient, and gardeners seeking truly perennial plants are probably best sticking to E. purpurea varieties and giving them good drainage. That cheerful daisy flower will no doubt continue to seduce us, however.

How to grow

Echinaceas need full sun and fertile, well-drained soil.

Avoid damp spots and heavy mulching over crowns in winter.

Deadhead to encourage flowering into the autumn after the main August-September season.

Once planted, they are best left alone — they do not transplant well.

E. purpurea and many hybrids flower the first year from seed. The elegant E. pallida is slower to establish but may be very long-lived.

Give yellow, orange and apricot hybrids extra-sharp drainage.

Sow seed as early as possible in the year, undercover, to allow for maximum growth; plants should be flowering by September — treat any that survive the winter as a bonus.