There is a wide, short border in my garden that I'm constantly chopping and changing. South-facing and backed by a high wall, it is very sheltered and warm: the kind of situation found alongside many urban houses. A few years ago, when I felt it was time to start marshalling my plants into some sort of colour-co-ordinated state of being, I designated this area yellow-and-white, with the odd fleck of blue for cool contrast. After great frenzies of replanting, in soil rejuvenated with lovely homemade compost, things bloomed happily in the summer sun. And the bright light reflecting off the pale moony and cheesy flowers produced a glare of migraine-making proportions.
Obviously something had to be done, but having spent all that good energy (not to mention the money!), I was not eager to look defeat in its ugly eye. Instead I fiddled around by adding more blue-flowered plants, including a giant echium (E. pininana), a native of the Canary Islands, now naturalised on the balmy south-facing slopes of Howth. The clue to the right direction in which to proceed came when this relatively tender plant failed to succumb to the ongoing, terrible freeze of Christmas 1995. Instead, its slightly frosted head branched into three stalks which, a couple of springs later, burst into pale-blue, 14-foot rockets of tubular blossom.
Its survival and subsequent towering proportions made it apparent that my border was something akin to a little outdoor hothouse. Images of banana trees and other exotics with expansive, generous leaves flapped languorously around my brain. And since then, in pursuit of that jungly vision, I have been gradually turning my erstwhile glarepatch into a soothing oasis: a place of respite for the eyes, where the luxuriant foliage absorbs the midday sun effortlessly and where the occasional unhurried turning of a breeze-caressed banana leaf gives an unexpected tropical thrill.
Of course, in real-life tropics, the banana would never grow beside the Chinese tree paeony or Siberian irises, but it does in my Dublin hot spot (the latter plants bear interesting, long-lasting, tatter-proof foliage: deeply and gracefully dissected in the first case and slenderly contrapuntal in the second). There is only one banana that can cope with an Irish winter - as I have discovered after unwrapping a neatly-protected column of mush in spring, the gooey wreckage of the tender, wrong variety. The Japanese banana, Musa basjoo, is hardy to minus5 degrees Centigrade (available from Garden Style, Baldoyle, for about £35. Tel: 01 8321640) and likes to be planted in a big hole with lots of extra drainage (gravel, grit, stones) so that it doesn't get soggy in winter.
The Chinese foxglove tree, Paulownia tomentosa (seeds from Chiltern and Thompson & Morgan), is another temperate candidate for my pseudo-tropical border. Left alone it will grow to a height of forty feet, cover itself in spring with candelabra of foxglove-type blossom and then produce large leaves. In this mode, and because it is tolerant of atmospheric pollution, it is grown as a street tree in parts of continental Europe. But if you "stool" it mercilessly each spring - which is just an ugly-sounding way of pruning it to near ground level - it produces preposterously huge leaves, as much as two or three feet across, held in a pleasingly symmetrical manner up its stem.
The annual castor oil plant, Ricinus communis (seed from Chiltern and Thompson & Morgan), is most often seen as a dot plant in bedding, its glossy palmate leaves lording it over a mob of marigolds or geraniums. But it's equally dramatic, if not more so, with its crisply outlined foliage forming part of a big-leaf patchwork. I grow the deep-red cultivar, `Carmencita', bearing in mind that, being a member of the Euphorbia family, all its parts are poisonous.
Another Euphorbia that looks perfectly at home in the Hiberno-tropical bed is E. mellifera, the Madeiran honey spurge, a near-spherical, evergreen shrub with elegantly-arranged lanceolate leaves and deliriously honey-scented, browny-orange flowers. The fact that it is adored by flies and wasps only adds to that special feeling of Borneo in the backyard. Birds, meanwhile - mostly wearing the impertinent bellhop livery of the blue tit or the sober brown suits of the house sparrow - love to hide amongst the clustered, tall spires of the lobe-leaved plume poppy (Macleaya) and to forage in the grey and bristly Echium candicans, two further strikingly exotic-looking plants.
In my south-facing, petite plot of make-believe subtropicality, all the plants like full sun, good drainage and shelter; conditions that naturally occur in this garden - and countless others all over the mild, sunny and sandy eastern coast. All must be slug-proof also: only the castor oil plant requires vigilance during its vulnerable infancy.
And now it's especially gratifying to see that, while the rest of the garden is fading into the crusty tones of autumn, all these over-blown giants are still in their unblemished, plump prime.