The 'Rhododendron Situation' and the Tricky Politics of Invasive Plants

View of Killary Fjord with fields of rhododendrons in foreground
Fields of rhododendrons in Ireland Deb Snelson / Getty

On Tuesday, an Irish politician gave an impassioned speech about rhododendrons. “The rhododendron situation in Killarney National Park has gotten so bad, minister,” Michael Healy-Rae expounded from the floor of the Irish parliament, “nothing short of calling in the army is going to put it right.”

The rhododendron situation! This tongue-twister of a phrase took on a delightful musical quality in Healy-Rae’s accent, and a clip of him, wearing a flat cap of course, quickly passed through the Twitter joke machine. The Rhododendron Situation: U2’s original band name. The Rhododendron Situation: horror movie. The Rhododendron Situation: sure sounds preferable to the American political situation.

We should acknowledge, before we go on, that it really is a situation. The species Rhododendron ponticum, native to southern Europe and Asia, has taken a liking to the humid climate and acidic soils of western Britain and Ireland, where the dense shrub has few natural predators or serious competitors. Its leaves are poisonous to animals. Its foliage is so thick that nothing can grow underneath. In 2014, two experienced hillwalkers had to be rescued when they became trapped in an “impenetrable forest” of rhododendrons.

In Killarney National Park, where rhododendrons are choking out the native oaks, conservationists have been doing battle since the 1960s. As the Irish Times writes, the weapons have evolved over time:

Horses and chains were used to rip mature plants out of the ground. Later methods involved cutting the plants at the stem and dousing the trunk in herbicide….Today the main method used to kill mature rhododendron is “stem injection”, making an incision with an axe or chainsaw and administering herbicide. For smaller saplings, workers cut the stem very close to the ground and spray it with a weak solution of herbicide and water, the “snip and spray” method.

Conrad Loddiges probably did not anticipate such trouble when he first brought rhododendrons to Britain in 1763. A famous nurseryman, Loddiges and his sons traded in plants for royal and botanical gardens showcasing exotic specimens from around the world. His second son, George, designed the hothouse heating and irrigation systems that let even orchids and palm trees flourish in England.

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Likewise, rhododendrons became part of horticultural exhibits. In modern times, the Inverewe Garden in Scotland, which has a famous rhododendron collection, has used the same stem injection method used in Killarney to kill certain seedlings, so they do not spread into the wild. But elsewhere, it’s already too late. Rhododendrons were also planted on hunting grounds to provide cover for game, where they quickly spread.

The plant went from something exotic to something ordinary a homeowner might have in their backyard. So ordinary, in fact, that the Royal Horticultural Society warned in 2014 that a proposed European Union law about invasive species could criminalize British gardeners growing rhododendrons.

And who gets to decide whether a foreigner belongs or not anyway? In different times and different places, rhododendrons have been considered exotic, mundane, or intrusive. The politics of invasive species always involves a value judgment about what time period should be privileged, which situation is “normal.”

Anyway, post-Brexit, Britain need not worry about any possible EU rules affecting the rhododendrons in its gardens. Ireland, on the other hand, would still like to get rid of the ones in its national parks.