I would spray while they are small. The seed will not all germinate at one time and you will need to spray again I am sure. Al

One of the guys at our local farm chemical supply store told me that Roundup does not work well against thistle. If you do spray with Roundup, I am curious to hear how well it works.

You are better off spraying when weeds are smaller than larger. They are easier to kill when smaller, I would think especially weeds like thistle.

Have you considered mulching with woodchips to control the weeds? It is non-toxic and will enrich the soil as it decomposes.

Thanks for all your advice.
As you can tell, Al, we still haven't sprayed.
The hill side in question is about an acre, so mulch isn't an option.
I will have to climb up to the fenceline to see if the RoundUp killed the thistles there. We don't want to use RoundUp on the hill because it would kill everything.
If we use a broadleaf weedkiller I'm aftraid it will also kill the wild flowers; but the concentration of thistle is so large that I don't think we have any other choices. :^(

I imagine you have yellow star thistle which is a problem here and worth the efford to clean it out. If your neighbor has it and only a fence separates you it will be constantly reseeding. Maybe you could plan a strip about 10 feet wide along the fence as a buffer zone with a landscaping allowing you to control the thistle without impacting the sest of the property. Al

I doubt regular Round up will work, but if you get some Round up "Pro", it should take care of it. Round up Pro has a "surfate" which makes the round up stick to the plant and kill it. It works 100% better than the regular stuff! You don't need to be a contractor or have a special license to buy it.

Al: It is Canadian Thistle that the county allowed to become 3 huge patches along Rt 168 which has now dispersed itself throughout our region.

Cagary: We have a permit to use the Ag form of RoundUp, and we make it into a 2% solution. This year we used one of the generic equivalents called "Credit".... mainly because it was safer to use around the Valley Oaks. It did indeed kill the baby Canadian Thistles where we sprayed... and everything else.

Go and get some Remedy. It will make short work of your thistle. Yes, it will kill all your wildflowers but the grasses will not be affected. You can always replant the wildflowers the next rainy season.

Westelle, if you have a permit to purchase some Ag Chemicals, Goal herbicide mixed with Roundup will probably knock out the thistle.

The RoundUp will also kill the grasses, which we don't want to do; they are native pasture grasses.

I haven't had any problem with Roundup on regular thistle (purple flowers). I haven't tried it on starthistle.

You can spot-spray on the hill using a piece of cardboard to protect adjacent plants. I've also seen roundup in a foam that would suit your needs, but I think it may be a bit expensive. If you really feel energetic you can get yourself good gloves and pull them out after a good rain. Most of them will slip right out of the ground. Those that break off can be spot-sprayed with Roundup. You certainly need to start doing something now. If the weather warms up suddenly they will get ahead of you and you will have a monoculture of them next year.

As I noted earlier, this is about an acre totally spotted with baby Canadian Thistles. I don't quite see me pulling all of them by hand. I can't see me pulling out all the grass in the back hill garden either... RoundUp with a spray guard there for sure.

We finally bought Ortho's Weed Be Gone Max and will try that --- as soon as it stops raining long eough for us to put it down.