Re: CULT: toxic Canada thistles?
- Subject: Re: [iris-talk] CULT: toxic Canada thistles?
- From: l*
- Date: Mon, 1 Oct 01 17:39:51 -0600
Hi Bill,
>There was no mention of allelopathy by this plant toward others.
>Which does not mean that it does not occur.
Interesting. I wonder if anyone has ever done a study looking
specifically for that characteristic of Canada thistle.
> However, CT has an enormous
>root system. A single plant may send roots more than ten feet in all
>directions, and as much as 15 feet deep in suitable soils, and consist of
>hundreds of aboveground shoots.
I'd like to see the doggone stuff just try to sink 15' deep in my solid
clay ... or wouldn't that be considered "suitable"? ;-)
>
>So it seems to me possible that even though the thistle shoots in the iris
>clumps were small, the iris roots may have been unable to compete with the
>thistle root system, hence the stunting of the iris.
That would seem to make sense, given the enormity of the thistle root
structure.
> The iris might also have been hurt by the herbicide
No, not in my case. I didn't even start applying an herbicide until well
after the iris clumps had already been devastated and sent into complete
dormancy by the thistles.
>By the way, many of the sites I found were about using other highly
>competetive plants to suppress CT. Alfalfa was especially effective
It is nice to know *something* can apparently compete with Canada
thistle and win. Alfalfa certainly has its merits, though it's not the
most attractive garden ornamental. ;-)
>Many of the sites expressed concern about CT rapidly developing
>resistance to most of the common weedkillers.
Gee, the news just keeps getting better and better.
>
>Also recommended was strict removal of any and all shoots as soon as they
>appear,
Easier said than done in heavy clay. The stolons on the young thistles
are extremely fragile and easily broken, and they're almost impossible to
remove intact from sticky clay. When they are inevitably broken off
rather than fully removed, the leftover underground portion will split
into numerous new offshoots, and you end up with 4 or more new thistles
where previously there was only one. AAARRRGGGHHH!!!
> and the avoidance of cultivation. Cultivation cuts up the roots and
>each tiny piece produces a new plant.
Which no doubt explains my fantastic failure at control via hoeing this
year.
>Then new seedlings come in.
Oh goody. More good news.
>
>Luckily CT does not thrive where summer temperatures regularly go above 90F.
>We do not have it here in Piedmont VA
Hmm. And just how are hobby farm prices out your way?
How did we ever get so lucky in the frigid north to have been so
successfully invaded by Canada thistle? Oh well. At least we don't have
any poisonous snakes or spiders.
Laurie
-----------------
laurief@paulbunyan.net
http://www.geocities.com/lfandjg/
zone 3b northern MN - clay soil
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