Sandy's Garden ... Ruthless Rhodies

We were returning home when a great splash of purple caught my eye in Larbert Woods just after we had passed Junction 1, the turn-off for the A883 to Denny.

Tuesday, 22nd June 2021, 9:02 am

There could not be the least vestige of doubt about its provenance – Rhododendron ponticum, an invasive immigrant plant which has found parts of the United Kingdom very much to its liking and has spread happily from estates and gardens to moorlands, uplands and partially-shaded woodlands.

Although I don’t know this for certain, I have little doubt that the area in the Big Wood covered by these shrubs is an area where a few bushes which were originally planted in the extensive grounds of Larbert House have become naturalised and have spread … as they do … by means of the suckers which spring from the roots and, to a lesser extent, by the plants’ prolific seeding characteristic.

These rhododendrons are ruthless killers once they become established, their large leaves depriving other plants of sunlight and interfering with the natural distribution of rainwater and thus sucking the life out of them.

Falkirk Herald gardening guru Sandy Simpson
Falkirk Herald gardening guru Sandy Simpson

Lovely to look at, / Nice to admire / But once they’re established / They’re real plant vampires!’

Rhododendron ponticum was first brought to England from southern Spain near Cadiz in 1763 by Conrad Loddiges. Initially it was unpopular; its mauve flower colour was unfashionable at the time and it was also relatively expensive to buy.

It began to propagate itself reducing the cost of seedlings and by 1849 the plant suddenly became fashionable as an ornamental.

However, the winter of 1894-5 was severe even for this species and following this the plant was used mainly as a grafting stock for less vigorous species and in hybridisation.

And yes, I do have several ornamental rhododendrons in my own garden and take pleasure from their showy, colourful flowers. I shall confess that I find their suffocation of smaller plants useful, for most weeds cannot survive beneath the combined umbrella and parasol which is the canopy of even a small, low-growing variant.

The downside is, of course, the need to beware of unwanted suckers and the advisability of removing spent flowerheads before they can start distributing their huge numbers of seeds.

But my rhododendrons are ornamentals which are very unlikely indeed to become a problem for any of my few neighbours, none of whom are foresters. If the Forth Valley Health Board, the current owners of Larbert Woods, were to wish to ‘re-tree’ the area colonised by their rhododendrons, it would have a tricky job to get rid of them.

Using volunteer labour to have a cheap ‘rhody bash’ by digging them out is very hard work and very inefficient; a mechanical flail is effective but very expensive; using trained staff to cut the stems and then apply specialist herbicides is both labour-intensive and very expensive; and injecting the bushes with herbicides, while very appropriate in hospital grounds, is still essentially at the experimental stage.

So, gentle reader, if you have the opportunity to enjoy a view of these massed rhododendrons, spare a passing thought for foresters while you relish it.