Gardeners are forever trying to trip each other up when it comes to identifying plants. Recently, within minutes of entering the gardens at Mount Usher in Ashford, Co Wicklow, this writer fell flat on her face by misidentifying a large shrub with plump, heart-shaped leaves. "Some kind of Cercis?" I ventured. And immediately regretted it when I saw a smile spread across the face of head gardener, John Anderson. Cercis, or the Judas Tree (so called because Judas Iscariot was supposed to have hanged himself from it - when he wasn't doing the same thing from the elder tree) bears clusters of elegant pea-blooms in spring. This impostor, however, was carrying spidery little flowers now, in October. It was Disanthus cercidifolius, John explained kindly, a tricky plant that likes acid soil. The cercidifolius bit of the name translates as "Cercis-leaved", so I had, in fact, blundered into the trap exactly as intended. But who cares? You don't need to know its name and family to appreciate the spectacular show of colour the Disanthus is making right now. (It is, for the record, a member of Hamamelidaceae, the witch hazel family - which accounts for its spindly, leggy flowers.) Its leaves, which maintain a dignified bluey-green tone all summer, become wildly flushed with crimson and deep wine-red in autumn. Mount Usher's specimen is about 70 years old, and is just one of the many trees and shrubs planted by the Walpoles, the original owners, to flame up in the autumn garden.
The Walpole family began to create the gardens about 130 years ago, in a naturalistic manner after the style of the champion of wild gardening, William Robinson. Full advantage was taken of the River Vartry, winding its wet way through the vegetation. Nine weirs were constructed to tilt the flow this way and that, over little gushing falls that make a constant music, and onto glass-smooth reaches that mirror the plants. Elegant suspension-bridges were stretched cobweb-thin from bank to bank, allowing the eye to pass right through them.
The Walpoles amassed an important collection of beautiful trees and shrubs from around the world, and they placed them within the gardens with utmost artistry and sympathy. In 1980 the gardens were bought by Mrs Madelaine Jay. Although not a gardener herself, she was captivated by the romance of the place. As John Anderson explains: "Some people want to put manners on a garden, but we feel that nature is doing its best. We're just helping it a bit." And in deference to nature's efforts, no chemicals of any sort - no fertilisers, pesticides or weed-killers - are used at Mount Usher. At this season, the genius of the original plantings is evident in the spread of autumn colour throughout the gardens. As the weather gets colder, the leaves lose their green chlorophyll - its work of converting energy is finished for the year. It fades away, leaving behind red and yellow carotenoids which glow all the brighter when the nights are very cold and the days are very sunny (not this year, alas). In Mount Usher, the colour is concentrated along the river's edge where it is reflected back again, giving double the spectacle. Duplicated in the smooth water are the red, yellow and purple leaves of Parrotia, the Persian ironwood tree; Liquidambar, the sweet gum; Cercidiphyllum - another Cercis doppelganger; and Nyssa sylvatica, the Tupelo (or "Elvis Presley tree", as John Anderson calls it, after the singer's birthplace). A short walk of red-and-yellow-inflamed maples brings the visitor to the river, while another avenue of autumn-coloured azaleas leads off invitingly into the distance. And here and there throughout the 20 acres, fiery leaves flash alluringly, drawing you further and further. There are 5,000 different varieties of plant here, all catalogued and carefully monitored, but it doesn't matter if you can't tell your arum from your elm, the watery spirit of Mount Usher works its romantic magic on everyone. Mount Usher Gardens, Ashford, Co Wicklow, are open daily 10.30 a.m.-6 p.m., until November 2nd. Adults: £3; OAPs, children and students: £2.50.