We all like to see a few thistles, and indeed, they are an important part of the natural balance on any farm. They provide food for a large number of Birds, Animals and insects and grow in conditions unsuited to many other plants.
They can, however, take over and along with Docks, were one of the things that many of us worried about when starting to farm in a natural system. I remember as a boy, accompanying my father cutting thistles by hand, and still carry a thistle cutter wherever I go, though I have evolved my thistle cutting tool of choice from the loyal “swing king cutter” , now about 50 years old, to a light mattock which seems to do a good job !
Standing in a field of clover herbal ley some months ago, faced with a vista that was carpeted with Sow and Bull thistles so thick that little else was visible, and without the comfort of the armoury of herbicides on which we have become dependant in recent years, I must admit to a feeling of creeping panic. In the past, we would have sprayed and be done with it – the thistles would have gone… for the moment at least ….. and we would have kicked on, oblivious to the deeper message that they were sending about the ground they were growing on.
It has always been clear, farming at Mindrum, that one ignores the message that the ground is sending at one’s peril. As I have mentioned before, a farm, particularly a marginal farm is like a rather bossy aunt. One needs to listen to what it is saying in order to manage it effectively. Of course this was less clear when we were deploying a conventional agrochemical paradigm, as there were tools to deal with almost every symptom or issue that arose, without the need to engage the place – in effect we were able to “impose production” on the ground – at least in the short term. (This may have been illusory!) Of course this effectively disengaged the battery of natural controls that evolution has honed over millennia. Having taken the decision to re-engage nature’s control set, we are having to unlearn the conventional doctrine and re-learn the rules of the natural toolkit. Significantly, our “situational awareness” and operational intelligence models also need to change if we are to understand what is actually going on and why.
Having spoken to many folk on the same or parallel paths as myself, I borrowed the book ” When Weeds Talk” by Jay McCaman and started digging into the area of natural plant nutrition, and started looking at the roles that particular plants play in a natural ecosystem. As a warning, “When Weeds Talk” is not a roller coaster of a thriller, but is more of a reference (albeit in an American context) but what it was saying mapped closely to what I was seeing on the ground and made sense. In essence, a natural system will fill empty ground, and will deploy plants which will fill the gaps. It would appear, that our conventional system, which deploys agrochemistry in lieu of natural biology has inadvertently created a biological soil profile which, without chemicals, is ideally suited to early successional plants and weeds such as Thistles, rather than the productive crops and ground covers which we are seeking to establish.
Like everything, the system is both complex and context specific but as a general rule, most Thistles (there are some species specific characteristics) are indicators of Compaction, a low Calcium/Magnesium ratio in soil and indicate local nitrogen. If we look at the architecture of thistles, they are well suited to this environment – many have strong deep tap roots which can drill down through the toughest of layers to collect calcium and a raft of other micronutrients from the deeper layers of the ground, often below a compaction layer or plough pan.  In addition to being outstanding foragers, they are opportunists and will grab other resources that are available.
/rgua====Many species, particularly the biennial thistles, will store these goodies in their tap roots – which often resemble prize parsnips. We also noticed that when conducting worm counts – in almost every case, the worms were more numerous close the thistles. This suggested denser microbiology around thistles and  was subsequently confirmed with a microscopic assessment.
When thistles come to flower, they pump stored nutrients above ground into flowers and seed. When we “rob” this by cutting and spreading them, they have to pump up more reserves, and also push more exudates into the soil to attract bacteria which mine more nutrients from the soil. This is where the opportunity lies…..
We have a field which has always been stony, low calcium/magnesium due to the underlying soil. We have always had a sow and bull thistle problem – which, until recently, was addressed with herbicide. Of course, the problem didn’t actually go away as we weren’t actually correcting the problem, merely managing the symptoms. Currently in a low clover based ley, we started topping it in May, just as thistles (huge at that stage) were beginning to bud. We have now topped it 4 times. After each topping (which spreads nutrient rich thistle pulp over the field) the thistles come back, but each time smaller and weaker. In particular, the tap roots, which started like prize root vegetables now resemble bits of chewed baler twine and are looser in the ground. The aim is to use the thistles as nutrient pumps, nutrient stores and also, as their roots shrink, to create air channels in the soil.

The old English rhyme about thistle cutting “Cut in May, they’re here to stay, Cut in June, they’ll be back soon, but in July, they’ll surely die” is instructive here. Its all about picking the moment when they have pumped all their reserves onto the surface. Though if one is also trying to stop them seeding, timings may need to flex. Pulling together a number of threads, both historical and current, we try to turn the tables and use the thistles to our advantage.

I await the results of some soil tests and tissue samples, but it looks to be working! Other fields, subjected to the same treatment last year are markedly cleaner this year.
Of course we are not just cutting thistles, by minimising soil disruption, actively managing livestock and diverse plant species in the ley, we are working hard in these fields to create a biological profile which selects for more advanced, mid successional plants, and which, in theory will ensure that the ground will select for our target ground cover (herbal leys and productive crops) rather than the early successional thistles and other weeds.
In essence, our strategy is to create conditions where our target crops are more competitive than our “weeds” (thistles etc). Rather than seeing thistles as a problem, we are using them to pump nutrients to the surface and making them part of a sustainable and cost effective solution.
…. at least that is the theory!!