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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.
Method
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).
Preventative
measures
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.
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