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This
is a prime site for Canadian or Creeping Thistle. The
ground is undrained / wet, and this plant thrives on moisture
without fertility. The land is almost permanently grazed
by sheep, which makes light much more available. Plants
densities are at least 400 to 25 square metres, when an
almost greater area appears to be covered by thistle rosettes,
than grass (See photographs). .
Density:
often 150 rosettes per 9 metres sq. Never less than 10
rosettes per 9 sq. metres.
Action
taken: 24 man hrs Chisel-hoeing below the point of
growth. May 1st 2003
72
man-hrs Chisel Hoing below the point of growth. May
30th.2003
A
workforce of four tackled this job with Chisel Hoes in
two separate visits. Early May & late May. This allowed
one area to be chiselled twice, and where the impact of
was greatest. Small 3 metre sq. plots were marked up,
and the re-growth (or later-growth) was counted. In areas
chiselled twice, the late rosette count was half of that
in areas chiselled once. In August, the whole site was
mown by an old tractor & reciprocating knife bar,
which further reduced the vigour of the rhizome. Before
2003, the only treatment had been occasional scything.
An
inspection during the summer of 2004 (a very wet time
and ideal for Creeping thistle), showed that the 2003
work had made a considerable impact, reducing the number
of shoot-rosettes from this particularly happy rhizome
by at least one third.
More
work with chisel hoes was needed to tame it further.
Total:
12 Man-days
Cost:
£720. ( or £72 per acre)
Assessment:
this is an on-going and expensive trial, with observations
and actions still being planned. The plant has been weakened
& seeding prevented, but the rhizome is still extremely
vigorous. It will take two more consecutive years of chiseling,
before long term control has been achieved. Cutting of
late rosette groeth & re-growth, using a wide wheel
based ‘Allen-type’ cutter, was recommended. This was done,
and for the first time in years, some form of control
of the Creeping thistle was under way.Three areas were
marked out for re-growth records.
See
below, graph of Canadian / Creeping thistle, confirming
the efficiency of chisel-hoe work (compared to pulling).
(graph
& research by J. Trevelyan. His thesis on Handwork
control of weeds is available, see web-site)
