Seamus O’Brien (1970–2025)

A plantsman, a scholar, a traveller and my friend

Like so many others, I am still coming to terms with the suddenness of Seamus’s passing and the quiet disbelief that follows news like this. He was such a large presence in horticulture, in Ireland and far beyond, that it feels impossible he is no longer with us. And yet, everywhere you look, his influence remains.

Seamus was, quite simply, one of the great horticulturists of his generation. A plantsman of international standing, he combined encyclopaedic knowledge with an insatiable curiosity and an extraordinary generosity of spirit. He never guarded what he knew. Knowledge, for Seamus, was something to be shared, passed on, talked through, debated, tested and enjoyed together.

Many people have written about Seamus’s professional achievements, and rightly so. His work at Kilmacurragh transformed what was once an overgrown and neglected landscape into one of Ireland’s most important gardens. Under his stewardship, Kilmacurragh became a place of serious botanical scholarship, conservation and beauty, a garden with international standing and deep Irish roots. He knew every corner of it, every plant, their stories, and carried their history with him lightly but reverently.

Kilmacurragh was not just his workplace; it was his great project, his responsibility and, in many ways, his legacy. The restoration of the garden and the long-fought campaign to secure the future of the house mattered deeply to him. He had plans, ideas and an astonishing attention to detail, right down to tracking down original staircase spindles and negotiating the return of family contents from Australia once the roof was back on. It is heartbreaking that he will not see that work completed, but it is equally clear that Kilmacurragh will always bear his imprint.

Internationally, Seamus was recognised as one of the world’s leading plantsmen. His lectures took him across the globe. He sat on expert committees, judged major competitions and was honoured with awards that reflected both his scholarship and his practical horticultural skill. His Fellowship of the Explorers Club, the RHS Loder Cup and our own RHSI Gold Medal of Honour were not just accolades; they were acknowledgements from peers who understood the depth of his contribution. Few people bridged the worlds of academic botany, garden practice and public horticulture as seamlessly as Seamus did.

His books on the early plant hunters are lasting works of scholarship, particularly his writing on Augustine Henry and Joseph Dalton Hooker. He had an extraordinary ability to bring these figures to life, not as remote historical characters but as fellow travellers whose footsteps could still be traced in the landscape. His work on Frank Kingdon-Ward, still so close to completion, deserves to be finished. It would be a profound loss if all that research, insight and passion were not brought into the world.

But Seamus was never only about achievements. To know him was to experience his joy in plants, in travel and in shared discovery.

I was fortunate to know Seamus as a friend for almost two decades. Our friendship grew through shared journeys, quite literally. I was honoured to join him on one of his Hooker research trips to Sikkim. That experience opened a door for me, as it did for so many others. Anyone who joined what became known as a “Seamus trip” would go again tomorrow if given the chance.

Those trips were not easy. They often involved cold, rain, altitude, dreaded leeches, dangerous traverses but also long lovely days botanising with friends. There were moments of real drama too. On one occasion, driving along treacherous mountain roads, a serious landslide forced us to abandon the cars. We had to make our way down the mountain on foot, carefully navigating loose ground and falling rocks, a vivid reminder of just how far Seamus was willing to go in pursuit of plants.

For all his knowledge, Seamus was never pompous. He was patient, kind and endlessly generous with his time. If you asked the same question three times, he would answer it three times. He had a wicked, boyish sense of humour, loved a good game and laughed loudly at silly films. That lightness sat naturally alongside his seriousness of purpose.

Seamus did not just travel the world; he knew the gardens of Ireland intimately. He had green fingers and the patience of a true gardener. Kilmacurragh’s remarkable Tasmanian collection stands as proof of that skill.

I find it very hard to accept that I will never see him again. And yet, I know he will be with me always, in gardens, in books and, of course, in our memories.

When I reflect on my own life, some of its richest experiences are there because of Seamus. He expanded my world. He expanded all our worlds. For that, I will always be grateful.

Our deepest sympathy goes to his mother, his family and all who loved him. This loss is sudden, shocking and deeply unfair.

We will miss him. Kilmacurragh will miss him. Irish horticulture will miss him. And many people around the world will miss him.

Thank you, Seamus, for everything you gave us, so freely, so generously and with such joy.

Orlaith x