The Control of Scotch/Spear Thistle (Cirsium vulgare)
This biannual can infest new seeds, pastures, crop margins and fencelines. Some fields retain a large seed-bank, and surprising proportions of land can be covered by the plant after reseeding. We once calculated that nearly a third of a 6.5 acre pasture was covered in rosettes. After a determined effort with our tools, the same field took one man just two hours to clear of rosettes in following years. Many of these new rosettes sprung from the seed-bank, following winter sheep-grazing.
Anyone who has topped their pastures, will know that Scotch thistle responds to cutting by coppicing and then growing an increased number of seed heads, which are too low for mechanical cutting. Our approach is to uproot this plant at the two leafed or small rosette stage, during autumn, winter & early spring, when the land is moist. The nose for doing this job is the ‘sheep’s foot’ (NO1b). We don’t leave them until late in the Spring, when the ground has hardened and the roots have become long or engaged in subsoil.
The crowns of maturing rosettes divide into several roots during the 2nd year (or end of the first), and each root can produce a viable seed-head, if it is left exposed in the ground. So we try and get them young. There’s no need to remove the uprooted plants from the field or crop (as with docks & ragwort), so just leave them on the surface to wither & die.
The first year of grubbing out a badly infested pasture or ley, can seem like an impossible task, and it is not really a job for one person (unless he is known to be fond of his own company). Always try to work in gangs (minimum two), and organize some kind of methodical line. We often use the tyre marks of vehicles to make parallel lines, so that the whole field is walked methodically. It’s sensible not do too much on the first day, because the technique doesn’t come immediately. Two good hours might well be enough. The ultimate aim is to uproot each and every potential flowering rosette from the ground, and after the first batch of uprooted thistles have withered away, follow up is necessary, to deal with missed plants. If the team keeps going and completes this first year attack, huge improvements will be seen in the following season. We recently cleared 12 acres of 8452 rosettes in 2.25 man-days (using inexperienced labour and five separate visits to the field).
1) Less tight grazing and paddling of land, leads to less thistles.
2) After the first clearance of a field, a conservation crop allows the land to repair and shade any lurking seed-bank. Hay crops are an old ploy to discourage thistles.
3) It will always worth be checking over the field, after it has been grazed. A ten minute visit to stock can be combined with a little weeding, if the tools are at hand [The Lazy Dog & ‘sheeps-foot’ nose, the Chisel Hoe, the Weedhook.].
4) Thistles are not able to grow in tree-shaded areas of fields, but do grow in hedge bottoms, where the light creeps in. We remove these awkward plants late in the 2nd year, by cutting them off at ground level with a weedhook, and bonfiring them.
5) Do everything to keep on good terms with your neighbours, because Scotch thistle seed blows a long way. Best to offer help and spend an hour with a weedhook in the fence-line.
CREEPING THISTLE (Cirsium arvense) & THE NEW CHISEL HOES
‘Chisel out two, and get a weaker one back’
This rhisome-connected thistle can be attacked within 2/3 weeks of the first appearance of rosettes in early April. By May rosettes are about 6″ high (in North Yorkshire), and we chisel them just below the ground, where the stem is still white. If they are cut higher up, in the green part of the stem, vigorous tillering occurs at ground level (as happens after normal mowing or topping). Chiseling them just below ground level, forces the plant to re-shoot from another point along its’ rhisome. This regrowth will appear quite quickly, but it is a weakened form of the plant, less prickly, shorter and unable to achieve seed head maturity (except sometimes in really wet growing areas). Research tells us that the vigour of this plant is almost totally dependant on moisture, and that fertility levels are relatively unimportant.
What are the immediate advantages of chiseling creeping thistle?
1) Pastures are cleared earlier, allowing access to a greater eating area for animals.
2) Animals do not prickle their noses in their search for clean grazing. This helps to eliminate orf in sheep.
3) The softer, less prickly re-growth, rarely reaches sufficient maturity to seed.
4) After chiseling, the induced re-growth weakens the plant rhisome from year to year, and on banksides (or any place where moisture is low), the annual improvement is dramatic.
5) On flat, well drained pasture, the cumulative effect of repeated chiseling, not only leads to clearer grazing, but weakens the plant annually.
The plant does not like being chiseled at any stage of its’ development right up to the appearance of seed heads, and there is no doubt that thistle beds that have had this treatment, will show the greatest improvements in the following season. If possible, repeated chiseling in the first season is worth doing, especially in the wet areas.
Mowing or Topping: this form of control can be effective long term, but only when it is carried out when the majority of thistle rods are approaching budding. Don’t do this it too late (and cause the seeds to mature on the ground), or too early ( and cause ground level tillering). Later cutting causes greater weakening of the rhisome.
Our all-steel chisel hoe has been developed over many seasons. It was
designed to be as light as possible and to enter the ground easily, using its’ own weight. This does not happen with shock absorbing wooden shafted tools. We use both hands and a rotary motion of the arms, and in dense thistle beds, achieve a strike rate of 35 rosettes a minute. We regularly sharpen the hoe blade with carborundum.