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Wipe Out! Getting tough with invasive rhododendrons

Rhododendron ponticum - invasive in Scotland
Brits usually have a more relaxed attitude to invasive plants than Americans, partly because they’ve been studied and mapped in Britain since the 1800s and relatively few have turned out to be really nasty. Now, in three different publications, the Royal Horticultural Society (RHS) has news of one, Rhododendron ponticum, that has definitely become a problem.

In Scotland, the Forestry Commission is planning to spend £15million (almost $24 million) eradicating every single plant of R. ponticum in its forests. Now that’s what I call taking an invasive species seriously.

The RHS membership magazine The Garden recently reported that the Forestry Commission believes that about 1,630,895 acres (that’s 660,000 hectares or 2,500 square miles) are infested. The dense evergreen growth smothers less pugnacious native plants. So this is a great scheme that will not only rid the forest of what the Forestry Commission describes as “one of Scotland’s most unwelcome invasive species” but provide valuable employment in these tough times.

Debris from the Lever and Mulch technique for removing Rhododendron ponticum.But how do you eradicate so very many plants, many of them large and long established shrubs, without chemicals, chainsaws or huge and heavy machinery? Well, another RHS magazine, The Plantsman, reported in June on a new technique called Lever and Mulch.

Developed by Gordon French and Donald Kennedy of Morvern Community Woodlands in Argyll in Scotland, their technique utilizes no chemicals but instead requires a pruning saw, a root saw, a hammer – and brute force – to detach the top growth from the roots. “This method is as eco-friendly as it gets, and can be done by a single fit person using gloved hands, booted feet, body weight, hammer, saw, L&M specific skills and a hearty lunch,” says the Lever and Mulch website. The stems and foliage are then left at the site as a mulch to help prevent seed germination. You can find out more on this technique at

Finally – it turns out it’s not R. ponticum anyway! A piece in Hanburyana, the occasional journal on taxonomy and nomenclature from the RHS, reveals that the plants in Britain usually referred to as Rhododendron ponticum are, in fact, not! Recent studies have shown that in fact they belong to a rather variable and unusually vigorous group of hybrids between R. ponticum, from eastern and southern Europe, and three American species - R. catawbiense, R. macrophyllum and R. maximum. And they’ve been given a name: Rhododendron x superponticum. For more information download Naturalised Rhododendrons by James Cullen.

But whatever it’s called, it’s days in the Scottish forests are numbered.

The image of Rhododendron ponticum is used under the Creative Commons Attribution-Share Alike 3.0 Unported license. More here. The image of Lever and Mulch in use in Scotland is by Donald Kennedy. Thank you.