“Tae Scots yer mair than just a flower,
Yer a symbol o’ great strength an’ power, Wrapped in shades o’ purple an’ green,
Yer the bonniest flower this land has seen. Some folks say yer jist a weed,
But we Scots ken yer a mighty breed.”
From ‘Tae a Thistle’, author unknown.
As every farmer and gardener knows, the thistle is not confined to its cultural home over the border (Scotland, not Somerset), and to many it is a thorny issue—pardon the pun. There are 12 true native species of thistle in the UK, belonging to three specific genera within the daisy family (Asteraceae). They have splendid names, including the woolly thistle, marsh thistle, tuberous thistle, welted thistle, musk thistle, slender thistle, carline thistle and my personal favourite the melancholy thistle.
But there are two which are the scourge of farmers, creeping thistle, and spear (or bull) thistle. Both are legally classified as so-called “injurious weeds” under the UK Weeds Act 1959 due to their aggressive ability to suppress establishing grass swards, and I will come back to them later on.
So why are we talking about thistles in the R-Word? Well their strength as a prolific and vital early to mid-stage pioneer species when arable land is being ‘reverted’ to nature, means that they often turn up in conversations about rewilding, and also in rewilding locations. In my ‘go-to’ book, Wilding, Isabella Tree describes the ‘Thistle Crisis’ at the Knepp Estate. While facing pressure to use chemicals to get rid of a vast 60 hectares of creeping thistle, Charlie and Issy held their nerve and millions of Painted Lady caterpillars arrived to destroy the infestation restoring balance to nature. This was a risk, but it was ultimately a good call and successfully reduced the thistle numbers without chemicals.
There are still creeping thistles at Knepp, but not in the same quantity, and they are seen as the brilliant providers of natural services that they are.
So what is it that thistles do for nature (and for us)?
Soil health: The deep taproots of the spear thistle delve deep into the subsoil, drawing up locked-away nutrients, and breaking up compacted soils allowing water to permeate—leading to increased organic matter lower down the soil horizon. Creeping thistles have rhizomes, that spread laterally in the soil increasing organic matter which can break down into nutrients;
Biodiversity: Thistle flowers are incredible nectar sources for a variety of pollinators, including bees, butterflies, and hoverflies, and the marsh thistle has been officially ranked as the UK’s single top nectar-producing plant (UK Insect Pollinators Initiative). The leaves also serve as essential feeding grounds for the caterpillars of several butterfly species, such as the Painted Lady, referred to above.
Food and nesting materials for birds: Once the flowers go to seed, they become a primary food source for seed-eating birds like goldfinches, linnets, and siskins—it wonderful to see a flock of goldfinches bustling around a thistle patch. Many of these same bird species also use the last year’s fluffy thistledown to line and insulate their nests.
Natural tree protection: In areas where trees are being allowed to grow naturally, such as many rewilding projects, thistles act as natural tree guards, with their sharp spines deterring large herbivores such as deer, and creating protected micro-habitats for young trees to thrive. You will have heard of ‘the thorn as the mother of the Oak’, well this is the same thing but closer to the ground.
Over-wintering habitats: Even after the plant dies back in autumn, the dry, sturdy stems and bulbous thistledown dominated heads provide crucial shelter sites for insects, larvae, and other invertebrates.
To add to this, thistles can be beautiful and are a source of inspiration for artists, not just in Scotland—just have a look on Etsy at the amount of thistle art! From my own perspective I have probably taken hundreds of photos of thistles in flower, and I love both the variety of flowers and of the shape of the stems.
However, coming back to the baddies of this tale, there are the injurious weeds mentioned above. The ominously-named creeping thistle forms massive, dense clonal patches that can expand many metres per year, quickly outcompeting and smothering young grasses and wildflowers, and is hard to prevent because each fragmented root piece can lie dormant or actively sprout into a new shoot. Whereas the spear thistle form ground-hugging rosettes, which can expand significantly to the detriment of other species. It is triggered by ground disturbance—one of the three Ds of rewilding (Disturbance, Dispersal, Diversity) and can be problematic to fully remove.
You can see why some thistles may be problematic to those who manage the land, particularly on ‘improved’ pastures, or even for wildflower meadows, and why they would want to keep numbers down or eliminate them entirely. I can understand that, but as ever, it is about the right thing in the right place. Yes, clear them from the main parts of the fields that are fertile and good to farm—keeping some in the edges of course—but allow more to develop in the marginal fields, to provide the natural services described above for soil, biodiversity and to the ecosystem at large.
For gardeners, no harm in a few stunning thistles to add a “shade o’ purple an’ green” to your edges, but as usual, a balance is needed. In my front garden wilding patch the creeping thistle has taken hold, but if the painted ladies don’t come (very unlikely for such a small area), I shall try to borrow a goat for a day to restore a bit of balance—that is, of course, after the flowers have gone over and the birds have had their fill… and then I shall hold my nerve and see what nature does next!
Dr Sam Rose is a photographer and podcaster about nature and rewilding—see his website at whatifyoujustleaveit.info and increasingly out of date podcast “What if you just leave it?”. He also heads up the charity West Dorset Wilding (westdorsetwilding.org) and the Brit Valley Project (britvalley.org) but the views expressed here are personal and are not said on anyone else’s behalf.
