Mount Congreve: The exquisite Irish garden on an unimaginable scale

It is the scale of the garden at Mount Congreve that bowls you over — its size, its massive plantings and the huge number of different plants. Here are some facts and figures: Mount Congreve has 70 acres of woodland garden, four acres of walled garden and 10 miles of paths. There are more than 1,200 rhododendrons, 760 camellias, 300 Acer cultivars, 600 conifers, a nearly one-mile path lined with hydrangeas and thousands of herbaceous plants, including 600 yards of hostas.

Mount Congreve is in Co Waterford, not far from the city of Waterford itself, but perched high above the glorious Suir, one of Ireland’s best trout-fishing rivers. The history of the estate goes back to 1760, when John Congreve built the first house on the site, but the spacious shape of the present house and its garden are the work of the late Ambrose Congreve, who died unexpectedly in 2011 on a visit to London for the RHS Chelsea Flower Show — at the age of 104.

Congreve was a remarkable man. His conventional Anglo-Irish background sent him to Eton and Trinity College, Cambridge, but took an unusual turn when he then went to work for Unilever. In 1935, he married Marjorie Glasgow, whose American father owned a worldwide business that specialised in building gasworks. After the Second World War, Congreve took over the management of the company and eventually sold it, rather well, in 1983. In the cash-strapped post-war years, American money was a blessing for the garden. As late as 1989, Congreve employed more than 40 gardeners.

He began to develop Mount Congreve seriously in the 1960s, extending the house and starting to plant the garden that we see today, always with help from an exceptional Dutch head gardener, Herman Dool. The focus of his planting was a stretch of north-facing native woodland — oak, beech and chestnut — on the steep bank between the spacious lawn behind the house and the river below.

If you look at it on a map, the garden seems very long — at least one mile in length — and thin, but the paths are so carefully planned and the plantings so dense that you don’t notice that, in places, it is less than 200 yards in width. The soil is a crumbly, sandy clay, enriched by a great accumulation of organic matter in the top layer and with a pH that is perfect for acid-loving plants. The climate is mild and damp, with an average of about 42in of rain per annum; many of Mount Congreve’s plants would be too tender to survive further inland.

Open the garden door in early spring and you come face to face across the lawn with a spectacular planting of magnolias, the oldest in the whole garden: you will seldom see such tall and beautiful specimens of Magnolia campbellii, M. x veitchii and M. sprengeri var. diva. They are planted just below the level of the lawn, which brings their individual flowers down to a height at which they may be admired. A better view can be had from a cupola, known as the Temple, Congreve built on a high point within the wood itself. It is surrounded by a grove of Betula ‘Fascination’ and the highly scented rhododendrons ‘Lady Alice Fitzwilliam’ and R. ‘Fragrantissimum’.

The temple, where the ashes of Congreve and his wife, Marjorie, are buried, also has wonderful views across the river below and deep into Co Kilkenny to the north and as far west as the distant Comeragh Mountains. Its dome bears the inscription ‘Light and Shade by Turn but Love Always’. This wise reflection is sometimes engraved on sun-dials and Congreve first encountered it in Leopold de Rothschild’s garden at Ascott, Buckinghamshire, which he visited as a teenager.

It was Leopold’s son Lionel, a great friend of Congreve’s aunt Lady Bessborough, who had the most significant effect on his style of planting. Visits to Exbury in Hampshire not only ignited an early love of gardening in him (aged 11, he recalled), but also persuaded him to garden in the same grand manner. ‘When one plants anything,’ Con-greve declared, ‘whether it involves five or 50 plants, they should be planted together and not dotted here and there.’ This was the maxim that guided him all through his many years of planting at Mount Congreve.

An early example of his large-scale planting, 70 years ago, required no fewer than 70 plants of Rhododendron macabeanum, a Himalayan species with large, silver-backed leaves and pale-yellow flowers. News of this grouping had the world of rhododendron-lovers chattering for many years and Congreve applied the same principle to R. sinogrande, another out-size species. Everywhere at Mount Congreve, the plantings are on the greatest scale — vast groups of azaleas, hillsides planted with thousands of candelabra primulas and an extensive grove of scarlet Embothrium coccineum trees that have taken so well to the conditions at Mount Congreve (similar to their own birthplace in Chile), that they seed around in their thousands.

The most spectacular of all Congreve’s plantings is the Magnolia Walk, near the furthest end of the woodland. It is an avenue — a straight walk downhill, about 150 yards in length, lined on both sides by three different layers of magnolias. The tallest is M. campbellii, usually in full flower by St Patrick’s Day on March 17, closely followed by M. sargentiana var. robusta, then M. x soulangeana keeps up the display until the beginning of May. It is easily the longest such avenue in the British Isles. The sight of these majestic trees seen in March against a Mediterranean sky is nothing short of magical.

Many plants now in commerce originated in this spectacular garden, including named forms of Pieris and Correa backhouseana, but its magnolias take the prize. These include M. ‘John Congreve’ and M. ‘Lady Irene Congreve’, which commemorate Ambrose’s parents, a yellow form of M. campbellii now known as ‘Valentine’s Torch’ and M. campbellii ‘Ambrose Congreve’, which is always in flower on his birthday, April 4.

One way to gauge the extent of the mature plantings at Mount Congreve is to look at the roll of remarkable trees published by the Tree Register of the British Isles. This lists more than 100 outstanding specimens, including large-leaved Aesculus turbinata, huge davidias (the handkerchief tree) and no fewer than three record-breaking species of southern beech, Nothofagus betuloides, N. fusca and N. cunninghamii. These are relatively widely grown in Irish gardens — the surprise is to come across outsize trees that are much rarer, including the variegated field maple Acer campestre ‘Pulverulentum’ and elegant, but tender Cupressus cashmeriana. An older specimen, although not yet a record-breaker, is a Monterey cypress Cupressus macrocarpa, planted by Princess Marie-Louise on the occasion of Congreve’s baptism in 1907.

Mount Congreve is not only an early spring garden. Large plantings of Clerodendrum fargesii and C. trichotomum are at their best in autumn, as are the leaves of maples: Acer palmatum ‘Katsura’, ‘Beni-komachi’ and ‘Shishi-gashira’ are spectacular. May brings clouds of the coral flowers of the azalea Rhododendron ‘Favorite’ and an amphitheatre of dwarf R. yaku-shimanum in the old quarry. Snowdrops, daffodils and bluebells carpet the woodland floor before the tree canopy closes over.

The four-acre walled garden and its glasshouses are now focused on the propagation and conservation of rare plants. However, a pair of borders, 60 yards long, runs up the middle, with an historic planting of rare herbaceous peonies in every available shade of pink, red and crimson, plus some whites and yellows. It is fronted by Nepeta ‘Six Hills Giant’ and backed by blue delphiniums, all shown off by swags of the roses ‘Paul’s Himalayan Musk’ and ‘Veilchenblau’.

When Congreve reached his century in 2007, he planted a Wollemi pine that had been presented to him by his staff. The gardeners also kept a spare plant in case the original should fail, but, in fact, both survived and the second, of whose existence Congreve never knew, has performed very much better. The staff still joke that, had it been possible, he would have planted a clump of 100 to mark the occasion.

The Congreves had no children, so the estate is now in the process of being transferred to the Irish State. The first priority of the Office of Public Works was to restore and secure the adaptation of the huge house from a plutocrat’s private residence to the public and administrative functions required in the post-Congreve era. The garden is, however, infinitely more important and this was recognised last year by the award of a plaque from the International Dendrology Society declaring Mount Congreve as Distinguished for Merit. Castlewellan in Co Down is the only other recipient in Ireland. Inevitably, the garden slipped a little after Congreve’s death, but its restoration is now galloping apace and a new School of Horticulture passes on the immense knowledge that it encapsulates.

Find out more at the Mount Congreve website.

This feature originally appeared in the April 8 issue of Country Life. Click here for more information on how to subscribe.