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Canada Thistle – Invasive Plant in Maryland


This is Canadian Thistle, this invasive plant is a threat to
natural ecosystems all over the United States. This particular plant is one of the
worst agricultural weeds in the United States. It’s been designated a Maryland
noxious weed and it is also, we get many, many calls about this because it starts
springing up in people’s flower beds and in their perennial beds.
Actually it’s not from Canada, it’s not native to Canada. It is probably from Europe and
maybe got here by way of Canada. You’ll see that Canadian
Thistle has a spiny leaf course. This is a good defense. It has a
nice purple thistle flower on it which will then brownout after a while
the thistle will head seed head will look like this and then each seed is
attached to a feathery structure, which then makes it very easy
for the wind to spread it. They can stay viable in your soil
for up to 20 years or longer. So you never want to let this
go to seed in your landscape. If you don’t have the time to cut
it down and treat the root system, whatever you do, cut off the the flowers so
it can’t produce the seeds. One thing you never want to do
with this root is rototill it. Every single piece, even the ones down to an inch in size
can regenerate a whole new plant. So don’t try to dig it out. If you have a small one coming up
in your yard just a little seedling, you can pull that out
if the ground is moist, if you make sure you get
every bit of the root, but as soon as it starts
getting some size into it, you really need to unfortunately exhaust the root system
one of two ways. You can, can continue to mow it and
cut it on a regular basis. So you use up all the reserves and
the system because the plant will keep putting up, trying to survive,
keep putting up new leaves. And if you keep putting it
off, cutting those leaves off, it will eventually
exhaust the root system. The other way to kill the root system
is to use a systemic herbicide like glyphosate. You remember that
this is a total vegetation killer, so use a cardboard or plastic shield to
protect your desirable plants so that the, there was no contact of the
herbicide onto your desirable plants. Be sure not to compost those flowers or
seeds because they will stay viable in your compost.

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