Thistles-Canadian

[Nate V. IA]

I've got a area about 1,000 sq ft of Canadian thistles that has gotten out of hand, is it too late to spray with roundup here in Central Iowa. This patch was about to go to seed in July and I disced it a couple times, the foliage died back but they are about a foot tall again. This is in an area I was going to reseed to pasture this spring but once the rain quit I figured I better save the seed until the forecast looked better, total area is about an acre but its not all infested.
Thanks
Nate
 

[DannyE]

Fall is suppose to be a good time to spray with 24-D, something about taking the spray to the roots for winter. Thats what I do, just did it last week.
Dan
 

[paul]

Perfect time for C-thistles! Spray!!!!

I've found strong glyphosate 2x esp a later spraying really takes them down. Let them come up a bit between.

--->Paul
 

[jackinok]

canadian thistle,takes two years to seed.first year they will be just a rosette type thing low to the ground,and thats the best time to spray. next year they make the seed head. if they have set seed already your wasting your time and money.next spring spray early ,and again the year after. if for some reason you cant spray or mow,simply cut the seed heads off ,drop them in a plastic bag and burn. whatever you do takes two years simply because they have a two year cycle. they really came on this year because of the drought made more bare ground where seeds could land and establish.
 

[paul]

_Canadian_ thistles have a lot longer life, so you certainly want to spray them in fall, their root mass keeps building, and they feed their roots in fall, they feed the bloom/seed in tthe first half of the year. Sap runs up in spring/summer, down in fall. You won't kill a _Canadian_ thistle in spring, only wound the top growth. The root mass will not be affected.

So, you want to spray _Canadian_ thistles now in fall, you will get the best kill this time of year as the plants are flowing sap to the large root mass.

They act like other thistles in that they are weak the first year they grow, and it's the 2nd year you really notice them. But _Canadian_ tthistles continue on as a dense thicket of a weed patch, regrowing from seed, root, and leafy cuttings, always creating topgrowth and seeds in the 1st half of the year, and feeding their root mass in the fall of the year.

_Canadian_ thistles are a perannual.

What you are describing are the bull, or Russian, or several other thistles, which are bi-annual plants.

_Candain_ thistles are a horrid thing, very very hard to kill. One needs to hit them right, and keep after them. Organically that are _very_ hard to get rid of, need to keep their patches black for a couple of years, so no vegitation sees the light of day - that huge root mass will keep trying to send up runners for a couple of years once a patch is established. Cut off any plants, and the green stem will send out rootlets and try to regrow itself.

They are a very hardy & tough weed.

The best time to spray them is after they set seed - unlike most other plants that go dormant or dead after they set seed - _Canadian_ thistles go into root-feeding mode and continue to grow through light freezes, feeding themselves for next spring. They appear to just be sitting there, but are actually very actively growing - seending all nutrition to their growing root mass.

They are a _very_ special weed for those of us in their prime growing areas who remember before Roundup..... Very special memories....

--->Paul
 

[jackinok]

most plants are hard to kill if you let them seed! sort of counter productive isnt it? one plant puts out a thousand seeds so you spray after the seed head burst so you can get the parent plant?. I know exactly what you mean though,your treating them like a half shrub. try spraying before the seed heads form fully, kill the top and you kill the seed .you wont kill the plant entirely,but youll stop its seeding,next year youll have less,spray again and youll have even less. another thing,try something besides 24d.it has very little residual. a product like chapparal might be better if you spray now. youll see a reduction next year.the trick is to break that cycle, but youve got to do it twice. and yes i do know what canadian thistle is,here in this state its against the law to have them in your field without doing some sort of control. big fines IF they enforce it. trouble with spraying in the fall here is its often too hot for spray to be effective. most folks here simply mow them often enough they cant seed in the fall,then spray in the spring with a herbicide with a good enough residual to cover the carb movement you describe. could just run some old cattle in there,here they eat them like candy! wont find one in a pasture here unless its sitting idle or its very understocked.
 

[GordoSD]

Grazon P+D after first frost.
 

[David Snipes]

The best thistle killer I have found is Milestone herbicide. It has a two year residual so you would not want to plant broad leaf crops for a couple of years.
 

[TomA]

I have been fighting bull and russian thistles most of my life. On these forums I learned about spraying them with roundup after fully in bloom to kill the root mass. You dont get rid of the existing plant but I am getting full extermination the next year. You need to follow up for a couple of years to get any survivors. They grow from the root mass not so much from seed unless you have loose ground.
 

[Jim in Sask]

I've had good results spraying 1 liter per acre of glyphosate plus a little 2-4D Ester or Estaprop late in the fall. After the first frost the plants start storing up nutrients so the chemical translocates throughout the plant and roots. It's also knocked down dandelions, fields are clean in the spring at seeding time.