Emma Townshend: 'The powerful allure of dahlias turns me into a Disney princess'

Outrageous deep-red cactus dahlia 'Summer Night' (Alamy)

Dahlias, they're like those Disney songs from the studio's 2013 smash hit Frozen. Big, bright, not in very good taste, nonetheless totally irresistible. In fact the only dahlias I don't get are the mostly very popular "Bishop of Llandaff" and friends; far too respectable, frankly, with small flowers, simple undouble petals and laughably ungarish colours.

Give me one of those Technicolor Disney princesses over the bishop, anytime: I like a flower to make your jaw drop. A flower that looks like a Spirograph drawing coloured in by a six-year-old weirdly fixated on the colour fuchsia. Something that would bring a pained grimace to the faces of the pastel-cashmere-wearing National Trust brigade. (And I say that as a person who loves to wear cashmere and then flash my NT membership card. But you know what I mean.)

The most trouble you'll have is getting them started. They come as a tuber in a plastic bag with soil, usually, and it's worth having a proper feel through the packet to check the root is still in firm shape – it should have the consistency of a very fresh potato. Not one that's been in the corner shop for weeks.

They need a nice pot, full of good, fresh soil Then you just wait for the enemy to attack. As Andy Vernon, author of this year's wonderful, The Plant Lover's Guide to Dahlias (Timber Press, £17.99), says: "Note that the local slug and snail populations can literally hear you placing them in the ground." He's so right. It's the tasty first shoots the molluscs really go for, and boy do they go for them. Many years ago I gave up on growing dahlias from tubers, because finding that some little plant I'd been nursing had been completely eaten alive during the night was too traumatic for me. Cue a full-on flouncy Disney princess tantrum.

But Vernon is a true dahlia prince, and it only takes one of them to get me back on track. So here I am once more, 2014, nursing those babies out of infancy. Following his strict instructions to mulch them with a mixture of compost and slug pellets (organic ones, he reckons), and provide a deterrent barrier, I am getting out the old favourite copper tape and slicking it round the tops of my pots. However his best tip is still mass killing: out on a rainy night with the torch and a bucket. Ewwwww. Is that going to make me feel all princessy? To be honest, I am heavily tempted (as always) by Crocus.co.uk, which is selling outrageous deep-red cactus dahlia "Summer Night" in full growth for £8.99. Financially, this seems a good exchange.

Dahlias are enormously greedy feeders, and will require a lot of watering. They'd prefer to have the whole garden to themselves, thank you, but will just about manage in your sunniest spot with your very best treatment regime. It's pretty much impossible to overfeed or water: Vernon recommends organic fertilisers, but specifies one intended for flowers, to avoid encouraging bushy leaf growth.

So if you are even slightly inclined to be horticulturally slothful, they are not for you. Just restrict yourself to viewing them, joyfully, planted in huge numbers, in the flowerbeds of National Trust houses. Oh yes, because it turns out that some of dahlias' number-one fans are National Trust head gardeners. It's almost as if a secret cabal got together and appointed them to lofty positions across the land, just so they could introduce a bit of bad-taste colour blaze.

But these days we're all agreed, surely: less is more? No. Because here's Vernon to set us straight: "More is clearly more."

For more on Vernon's favourite dahlias, go to: www.timberpress.com/blog/2014/05/ 8-dahlias-for-maximum-color/

Four more of Andy Vernon's top dahlias for colour

Bishop of York

Truly golden yellow is a surprisingly rare colour in dahlias, but this wonderful single with fabulous dark bronze foliage is probably as close as it gets.

Black Satin

This deep red-black formal decorative with 10cm-diameter blooms is a good, solid, prolific variety that produces lots and lots of sultry, satiny flowers.

Waltzing Mathilda

Peach-coral peony blooms, sometimes with a cherry-red blush, are brilliantly set off by dark burgundy-black foliage. A whirling dahlia dervish.

Little Snowdrop

A perfect white pompon variety of gorgeous globular blooms on good straight stems: adorable. It makes great cut flowers, and is a good border variety.