In the lifetime of the average Irish garden, it’s fair to say that a surprising number of its trees will never reach old age. Those that do are more likely to be the exception, their longevity the result of a mixture of good luck, good genes and good gardening. Of all three, it’s the latter in particular that we’re going to need most when it comes to meeting the growing challenges of extreme weather events caused by climate change.
If that sounds like doom-mongering, consider the arboreal death toll from last month’s Storm Darragh, a possible harbinger of things to come. At the historic National Botanic Gardens, Kilmacurragh, in east Wicklow – one of the seven “red zone” counties in Ireland worst hit by the storm – close to 140 mature trees were toppled as a result of its fierce northwest winds, which gusted to speeds well over 100km per hour.
Among those casualties were many venerable specimens, the garden’s “elders” that were and are such an important part of the rich fabric of its history. They included a silver fir (Abies alba) originally sent to Kilmacurragh by the 18th century Irish forester, writer and politician Samuel Hayes; a mature pencil pine, Athrotaxis cupressoides, planted in the 1860s and grown from seed collected in Van Diemen’s Land in Tasmania; several balsam fir (Abies balsamifera), a giant, centuries-old beech, and numerous other conifers that formed part of Kilmacurragh’s crucial shelterbelt. Left with a dauntingly huge, expensive and complex post-storm clean-up to oversee, its head gardener Seamus O’Brien has described it as “the worst storm in a century” in terms of the damage wreaked.
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Meanwhile, in the nearby historic gardens of Mount Usher, the same storm felled one of its oldest and most majestic trees, a much-revered champion Montezuma pine considered to be among the finest specimens of its kind in Europe. Look across the Irish Sea to Wales and a similar tragedy befell the famous National Trust-managed gardens of Bodnant, where more than 30 historic trees fell, including a specimen of Abies cephalonica or Greek fir planted in the 1890s.
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What to do? Clearly the answer isn’t to stop planting trees, which provide us with clean air, shelter, fuel and food and play a vital role in supporting and conserving biodiversity, as well as combating noise, soil and air pollution, soil erosion, and flooding.
Add to that long list of advantages the invaluable role they play in beautifying our cities, parks and gardens as well as the wild landscape. Just one small garden tree has the power to positively transform an outdoor space in a myriad of ways – environmentally, aesthetically, and in terms of its ambience and atmosphere – that can’t be equalled. To quote the American poet Ralph Waldo Emerson, “the wonder is that we can see these trees and not wonder more”.
But trees need our help when it comes to meeting the challenges of climate change. Part of the answer, confirms O’Brien, is the creation of hedges and shelterbelts designed to provide protection from fierce winds. In this case, careful selection of appropriately resilient, climate-appropriate species is key. He cautions, for example, against using very dense coniferous varieties such as Leyland cypress (× Cuprocyparis leylandii) and Lawson cypress (Chamaecyparis lawsoniana), both fast-growing non-natives which are so impermeable to winds that instead of filtering them, they act as a solid barrier akin to a high wall, resulting in further destructive turbulence. “They’re also shallow-rooted species, so they’re much more vulnerable to toppling in a storm.”
Instead, he’s focusing on using a generous mix of resilient native evergreen and deciduous species in the new, extensive shelterbelts being planted at Kilmacurragh. The list includes yew, holly, Scots pine, oak, arbutus, whitebeam (in particular, Ireland’s native Sorbus hibernica), euonymus, hawthorn and blackthorn. Most are grown from seed sourced locally both to minimise the risk of disease and further support biodiversity (unlike plants grown from cuttings, which are genetic clones of each other, seed-grown plants are genetically more variable, which cultivates resilience).
Another part of the solution, of course, is only choosing trees and hedging species that are suitable for your garden’s growing conditions. Yew, for example, hates to sit in a poorly drained soil, as does beech, with the result that they’re far more likely to succumb to disease in wet ground, making them more vulnerable to storm damage. But alder, hornbeam, birch and willow will all grow quite happily in those same growing conditions. Even then, different varieties within a particular species can vary dramatically in their vigour and resilience.
How to choose wisely? Part of the problem is that traditional advice on choosing garden trees tends to focus on their aesthetic role rather than their suitability for a particular site and the set of growing conditions that it offers. The role that climate change will play is also rarely considered.
Fortunately that’s not true when it comes to The Essential Tree Selection Guide by Henrik Sjöman and Arit Anderson (published by Royal Botanic Gardens Kew). Weighing up the increasing likelihood of extreme weather events combined with the further complications of urban pollution and growing risk of pests and diseases, it offers expert, up-to-date advice on selecting the most suitable species for our gardens, parks and streets, basing its recommendations on the natural habitats and growing environments of tree species in the wild.
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Good gardening in terms of both planting and maintenance is yet another important part of the solution. Young trees that are planted too deeply or too densely, or which are improperly staked are already going to be predisposed to disease and storm damage from an early age. Planting to the correct depth is vital (the root collar should be level with the surface of the soil), while stakes should be placed to the windward side of the tree and tree ties should be adjustable and regularly checked to prevent them girdling the young trunk. Newly planted trees should also be kept weed-free around the base of the trunk and watered regularly during their first two growing seasons, especially during dry periods.
Even then, the risk of pests, disease and drought remains, which is why it’s important to make a point of routinely inspecting your garden’s trees for early signs of plant stress such as discoloured foliage, dieback or loosening of the root-plate. “Trees,” as Kilmacurragh’s O’Brien points out, “will generally tell you when they’re unhappy.” In the case of clearly ailing or unstable trees, it’s best to bite the bullet and have them professionally assessed/removed rather than letting nature take its course.
Finally, it’s worth pointing out that the loss of mature trees to violent storms has always been part of the natural cycle of nature. When Hurricane Charley ripped through the gardens, parks, great woodlands and forests of Ireland and the UK back in 1987, for example, it wreaked enormous damage. But with time came the realisation that it had also provided the welcome opportunity for new plantings. The same is true of Kilmacurragh, where O’Brien is already considering replacements for the trees lost, in many cases using young saplings grown from seed harvested from the latter. The lesson? Life endures, our gardens teach us, even when the going gets tough.
This week
Check garden structures such as pergolas, gazebos, sheds, glasshouses and polytunnels for damage resulting from winter storms and gales. The same goes for large trees both in terms of displacement of their rootballs or damage to their branches.
Nip out the growing tips of autumn-sown sweet pea plants to encourage the development of side-shoots and plenty of strong, bushy growth. Bear in mind that sweet pea likes cool growing conditions, so don’t mollycoddle young plants indoors in a heated room, but do provide needed frost protection if the temperature is forecast to go below minus 4C.
Dates for your diary
Saturday 25th, Ballykealey House, Ballon, Co Carlow, Annual Snowdrop Gala, Celebrating Snowdrops and Other Spring Treasures, with guest speakers Keith Wiley of Wildside, Devon and Callum Hallstead, head gardener and snowdrop curator at Cambo Gardens in Scotland, plus specialist plant sales featuring snowdrops from Altamont Plants with Avon Bulbs Collection, Cold Blow Nursery, Assumpta Broomfield, Rosabell Plant Supports and Esker Farm Daffodils. See altamontplantsales.com for details.
