It wasn't until her husband, the gregarious journalist Tom McPhail, died six years ago that she decided she needed a qualification if she was make her living from the thing she loved most.

When the time came, she applied and was accepted as a FETAC student on a certified horticultural course at Glen College, Knockmaroon, Dublin, an intensive course for which she has nothing but high praise. After a year, Adelaide was sent on her first work placement to Farmleigh, the old Iveagh estate in the Phoenix Park that was now in the care of the Office of Public Works (OPW).

She fell in love with its carefully gardened 27 acres and came to work under Miranda Iveagh's former head gardener, Noel Forde. He had been retained by the OPW after Benjamin Guinness, the Earl of Iveagh, died and Miranda and her family sold Farmleigh and decamped to England.

"That was four years ago and I've never left it, " says Adelaide, who has a daughter, Sarah (a chef, currently working in Glasgow) and a son, David (a bass player, composer and teacher). "I'll probably stay here until I retire . . . unless I get a better offer!"

And she may well get a better offer, as gardeners as brilliant as she is are hard to find.

Adelaide has now proved herself as a contemporary designer, too, having completely remade her own back garden after it was knocked quite flat two years ago by the sudden collapse of a heavy hoarding between her garden and a neighbour's.

Last week, during one of those long hot evenings, I visited Adelaide to see it and was wowed from the distance by a superbly poised, densely massed block of the lovely, complicated, bi-coloured columbine, Aquilegia 'Nora Barlow' taking centre stage in her front garden.

'Nora B' and splashes of blue, white, yellow and pink compatriots filled one whole side of the open-plan, American-style garden, designed by the builders (Brennan & McGowan) in keeping with the modernist, flat-roofed, late 1960s houses tucked away in a quiet, leafy enclave in Dublin 6.

The other side of the front garden is filled with swathes of the pink hardy geranium G.

endressii and 'Johnson's Blue', with a good knicker-pink Oriental poppy on guard.

The door, front-of-house kitchen and compost bins are sheltered by a large variegated holly and a Pittosporum tenuifolium 'Silver Queen', a variety with fabulously scented flowers that can waft for yards on the night air in May.

Adelaide says she "yums" Aquilegia (remember she's also a chef) and . . . not one to do things by halves . . . she dug over that whole side of the garden and sowed "buckets of 'Nora Barlow' and a few other kinds".

It's a great success.

At the back of the house (under which the Swan River flows down to Rathmines), you step out through a wide wall of glass doors, onto a sun-soaked deck that faces due west, over the burgeoning new garden and beyond to a lovely overgrown orchard, the remains of one of Dublin's lost farms.

Adelaide's house is also built on the old agrarian farmland, so the soil, after centuries of manure, is excellent. Ever the dutiful gardener, she makes sure it stays that way, with liberal additions of garden compost and animal manure in December and January, "to condition the soil and give it a shoo along for when it's all happening. I try to organise the garden in a rolling scheme, so that it's constantly unfolding the rest of the time."

All around are big, open skies and there is no sound of the city, only of swifts and swallows catching supper on the wing, and blackbirds and magpies timing each other for bagsing the "swimming pool".

That's Adelaide's name for the dark, triangular and bluemosaic-lined pool she made at the far end of the garden, where a lovely old stone wall was revealed after she tore down the utilitarian shed.

Just as she took out the shed, and a big bay and two mature laburnums, there's no lawn now either. Hand tools are kept in a long, custom-built wooden box which doubles as seating in the stone-paved area around the dark, slate-backed pool. A wrought-iron brazier is used for parties and barbeques, and a table and chairs for taking breakfast outdoors in the morning sun.

"The only thing I kept was the Amelanchier lamarckii, which was never moved and has survived very well. I wanted the four elements of fire, water, earth and air in the garden, and I've got them. The decking is air. The earth speaks for itself, " she says, gesturing towards the lovely planting on either side of some dramatic steps.

"I worked it out with sticks and pieces of string until I got it right, " she says.

Adelaide spent ages working out exactly how she wanted the rest of the garden and, when she was satisfied, took out a bank loan to have the work done. She refuses to say how much it cost, but "the steps, in particular, gave my builders a really big headache and nearly broke their hearts.

It was their first garden and they really cut their teeth on it, but it's brilliantly done and now they're in huge demand for garden work."

Yet it's always plants first with Adelaide and she has filled her new garden with so many lovely and lovingly grown things you would never think it was still less than two years old, particularly as she bought some large, mature specimen trees (Acacia dealbeata and A. baileyana, a Koelreuteria, a Montesuma pine, a Sorbus 'Joseph Rock', a Ginkgo biloba, three large variegated Aralia and more) from Finlay Colley of Roscarbery Nurseries on the Naas Road.

She got a lovely collection of ferns and a well-chosen selection of ornamental grasses from Mt Venus Nursery, including the shapely Ampelmodesmos mauritanicus, which is used in its country of origin for tying up vines, should you want a way to recycle it.

Another cause for comment was the stand of beautiful red Hedysarum coronaria, which she grew from seed given her by nurserywoman, writer and broadcaster Carol Klein in 2004. This flowers for months on end and is a thoroughly good border plant.

Along the larch-lap fence, painted a very dark green so the eye does not "read" it at first glance, are wisteria, white jasmine, Billarderia (of the Pittosporum clan) and Parthenocissus. There are monkshoods and lots of self-sown poppies and forget-me-nots.

"Don't forget my Bonsai Wych-Elm, " says Adelaide. "It's been tortured for 17 years.

Bonsai is so cruel, the equivalent of Chinese foot-binding.

So I gave it freedom and it's doing fine, aren't you my pet?"