Stephen Anderton discusses the fashion for black-leaved plants like Dahlia ‘Bishop of Llandaff’, and is taken with the impulse to create an appropriate limerick

What is it about black-leaved plants that brings out such lust in gardeners? Why do we have to have them? Why, when a nurseryman describes Geranium phaeum as having “almost black” flowers, do gardeners drool and pull out their cheque books?

Partly it's the lingerie thing. People think black is sexy, and it is. Look at water droplets standing on the feathery foliage of black-leaved fennel after a shower (that's rain in the garden, not you fresh from the bathroom) and you cannot fail to be fascinated.

Everyone nowadays has to have the dahlia 'Bishop of Llandaff', even people who a few years ago were so snobbishly anti-dahlia that they would not allow one in the garden. Who, now, can resist that glittery black foliage, as black as you find on any plant, and those bright red flowers. It is pure Shirley Bassey, with the emphasis on the lipstick. (Perhaps that's how the eponymous Bishop liked to think of himself?) The Bishop may not be the best flower on a black-leaved dahlia, but she certainly has pizzazz.

Trouble is, it's not glamour and pizzazz that make the world go round. They may be fun, but they don't pay the rent. They make too little structural impact in the rational light of day. In a garden every plant needs to pay full rent for as long as it's visible, or it shouldn't be there. So think hard about how you use black-leaved plants.

They make a fine moment of contrast of course. Against a backdrop of differing greens, the occasional moment of black works well - clipped Pittosporum 'Tom Thumb' amongst box balls, or the black elder Sambucus 'Black Beauty' billowing up at the back of a deep border or shrubbery. The Bishop looking queeny in an autumn border of outrageous hot colours.

But more often than not black foliage looks best close to. From a distance it just looks like a hole in the general canopy of the planting. It is a non-colour really. But it does make an unusual and effective foil for other colours. That's why the pink flowers of the 'Black Beauty' elder look so delicious against the black foliage. That's why the pinkish flowers and the black-purple foliage of the cow parsley Anthriscus 'Ravenswing' look so good together. That's why a pot of the black aeonium looks so striking mulched with pink glass chips. That's why peachy eremurus or kniphofias look so chic spiking up through a sea of black fennel. It's the classic combination of flesh tones and black lace.

But the whole point of flesh tones and black lace is that they appeal close to, not from 30 yards away. Lacy blackness only has impact where you can get close to it. So use such plants lightly, for the more intimate moments of the garden.

The contrast of black foliage and pale stone or concrete is severest of all. I once saw a rockery bank planted all over with black-leaved lily turf, Ophiopogon planiscapus 'Nigrescens'. It looked like a lava-flow of Spotted Dick, every stone a white raisin afloat on the black dough. By the time the lily turf had matured and actually hidden most of the stones, it would have made a wonderfully textured shady bank. But for now it looked, well, very spotty. Such is the power of contrast of a large area of black. But maybe more carefully used, perhaps the odd square of lily turf in a paved courtyard, or several squares? Or several squares of the green form, and one black? The name of the game with black foliage is contrast. It is there to be played with. So have fun with the Bishop, but give him a hard time.

If you really want to have fun with the Bishop, apply your mind to completing the following limerick, and email the result to editorial@greenfingers.com.

Here's the first line:
An eager young curate from Llandaff,