Posted August 10, 2006: Canada thistle is a frustrating
weed. First off, understand that you will never eliminate it forever.
As soon as it is gone, seed drifts in from somewhere else and takes
hold. My objective is to manage populations to acceptable levels,
i.e. patches small enough to be mowed out of the crops. On the tillage
side, I use a spike-tooth cultivator followed by a rodweeder to
pull out the thistle plants. The spikes loosen the root, and the
rod pulls as much root as the strength of the root allows. I regularly
pull out 6 to 8 inches of thistle root, but the length will vary
by soil type, moisture and weed stage.
If you have thistle, get rid of all sweeps on your cultivators.
A sweep only cuts at the depth of tillage and allows for more competitive
I agree with Jeff Moyer on the use of hay and rye, but I will qualify
the rye idea: You must have enough soil health to produce at least
a 60-bushel-per-acre crop—any less, and you lose a lot of
competitive advantage against the weeds. I try to build the soil
with a plowdown crop first, seeded late spring to allow a flush
of thistle. Incorporate in late July, and seed to fall rye in the
first week in September after another spike/rod pass. Don't underestimate
the value of fall tillage on thistle either.
We commonly disc our rye stubble and what thistle may be left is
"pulled" out by the disk. The rod is useless in the heavy
straw because it will not clear the residue. Hay does eliminate
thistle, and it provides income at the same time.
The photo shows that Kongskilde has a specialized shank unlike
any other, one with a hook specifically designed to pull and kill
quackgrass. As a matter of fact, the original spikes for it had
a pull-out sheet on how to cultivate to kill quack.
One further detail on my cultivator set-up: Notice the type of
spring mount used. It is two band springs, eliminating any bushings.
The neat part is that it allows for movement side to side as well
as front and back. This gives a whole new meaning to term “vibra-shank,”
the critical action in shaking out quack roots.