Any organic ideas on controling canadian thistle ??We have 4 acres of field that I am trying to convert back to wild prairie and the thistle are winning ! Pulling them does not seem to slow them down.The burdocks I think I might finally have conquered and the box elders are keeping me quite busy also.

Unforturately I don't have a solution. I am also looking for advise on thisle control. My 6000 square feet of garden is contaminated with thistle that my tiller chopped up and did a beautifull job of planting it all over. The fact that the main roots are so deep makes it almost impossible to dig out. HELP NEEDED!!

Have you tried a boidegradable weed killer? I have had good luck with straight vinegar on some thistles around my property. There was someone who posted something recently about using a 20% type vinegar vs. the 5% kind from the grocery. They said that it could be purchased at their local feed store and it worked as well as roun*up. You might find the post if you do a search on vinegar?

Good luck to ya.

Keep the area mowed weekly and within 1 to 2 years you will be thistle free (okay if your neighbor has a problem also and is doing nothing you will be fighting a losing battle). It is especially important to mow them down when they go into full flower but before those flowers are made into seeds. Cutting thistle in flower will kill them (and prevent more seeds from getting in the soil to form a new generation).

If you have thistle in a garden area hoe it down weekly with a sharp shuffle/stirrup hoe, yes they will try to spread at first but you you are persistant with the hoeing they will give up after a few months. They can take only so much abuse before they die-despite rumors Canadian Thistle is NOT immortal ;-)

Thanks for the info NAtRGrl,
I work in the flavor industry and able to get 100% natural acetic acid. I will experiment with different concentrations and different methods of application. I guess these applications will lower the pH in these areas, but I guess that is a small price to pay for getting rid of this pesty weed.

PS, I will be out in California next month. I am hoping to visit by good friends in Woodlake and Soquel. It has been several years since my last trip and I am looking forward to the visit.

The problem with using chemicals for weeding (Yes, using vinegar is chemical weeding) is you will change the chemistry in your soil so while you may not get thistles any longer (as long as you keep reapplying the herbicide) you also will have changed the pH of your soil so that only acid loving plants will want to grow their. Remember that in a stand of thistle, most of the plants are from the same root stock so spot spraying will not be effective-you will have to widely broadcast the chemical for complete coverage.

Salt is another effective herbicide and will kill the thistle but will also ruin your soil, perhaps for decades, because of salination, so that you have a waste land and not a garden

Hmmm....interesting point.

"Yes, using vinegar is chemical weeding."
I'm not trying to be Montsanto here.
I cook with it, clean with it and keep it on hand to neutralize sodium hydroxide when making soap. I love the stuff! Using it in the garden wasn't much of a stretch.

All that I have read in the past has supported the idea that the vinegar solution will break down relatively quickly. Do you know where I can get more information on that?

I applied the solution to the leaves and stems of the weeds directly with very little overspray. Do you think that will make a difference in how much effect it has on the soil?

Up until this year I have always pulled all of my weeds by hand. (back breaking work, but very rewarding) I moved to a much larger property last year and have been 'less abled' since right after I moved in. (timing is everything) There are huge stands of thistle, nettle and mallow threatening to take over if I don't gently intervene. I have an enormous tick population, but I am leaving some of the weeds away from the house as an insect habitat. I am also planting a drought tolerant local wildflower mix to make up for some of the weeds that I am removing. Do you have an opinion about maybe trying to use a cover crop? The property that I rent runs right up against the fields of a neighboring farm and I do not want to take the chance of planting something too invasive. (dilemmas, dilemmas...)

Any input would be appreciated.

Hi Pepperman. Welcome to the posts! Sounds like you plan to be in the right place at the right time. The weather should be about perfect.
I hope you enjoy your trip!