Hello all, We really need some help here! We have just moved into a rural property in Saskatchewan. We're mainly concentrating on the house at the moment, but eventually we are hoping to set up a permaculture garden on the land here. We wanted to plant a shelterbelt this year however, as obviously trees take a long time to grow, so the sooner they're in - the better! Unfortunately, the area where we need to plant the shelterbelt is the old vegetable garden area and the vacated patch (the property has been vacant for about 8 years before we moved in) has been overgrown with Canada Thistle, dandelion, and I presume a whole bunch of other weeds. I have been told that the trees will not be able to compete with the mighty roots of the Canada Thistle, and we have to spray it with roundup!!! Noooooo! This is absolutely the antithesis of what we want to be doing with our land!!! Not only are we advised to spray, but we are also expected to spray multiple times. I have been frantically searching online, but it looks like there is no good solution to Canada Thistle and that it is the lord of the weeds. Can anybody give us any good suggestions of what we could do without the use of evil chemicals?
Lol, yeah thistle in general is tough to deal with. My area wasn't overgrown with it, but had a fair amount, bull thistle though and in not sure how the two compare. To be honest, herbicides aren't always terrible things. Using it in small "point of interest" attacks is a much different beast than drenching an entire field in it or dropping it from an airplane. Really the only other way to get rid of thistle is to dig it up, roots and all. Naturally some root will be left behind, which will regrow so the process with need to be repeated. Not sure about Canada thistle, but most thistles are edible as well, and are actually kinda tasty, just a thought (peel and eat the stalk).
If you're deadset against herbicide (and it will save you HOURS of intensive labor) dig out a large circle (8 feet?) around where you want to plant the tree, and keep it weeded. Should give the tree enough of a head start where it can eventually outcompete the weeds. I'd say use a natural herbicide (vinegar, etc) but they won't kill the roots and it'll only be a bandaid solution.
Or, crazy idea, just plant the trees anyway and see which ones survive. Depending on the trees they can be bought fairly cheap from your state departments. This assume you're not wanting select cultivars of fruit trees though.
Trees shouldn't have a problem competing with the Canada Thistle roots. It might be more likely that the trees will have more difficulty IF the Canada thistle is dominant because of compacted clay soil! If that's the case, select some trees that can handle the soil. Also plant trees that are already over 4' high and mulch them with say...mowed thistle, scythed thistle, chopped thistle, and pulled thistle.
thisles and dandylions are both deep rooted plants .they are there for a reason, to bring up nutrients. It is natures way of regenerating the soil. get a tiller and turn them over and do it a few times . lay down cardboard around your baby trees waterwells . plant grain (wheat, oats etc) heavily between the trees to out compete the thisle roots them chop and drop the grain latter in the season as mulch after the grain has headed out. This has worked for me numerous times. once in a while I get the odd deer munching if I plant barley though. Don't forget to water your babies though. and leave the dandilions alone , they are doing what they are supposed to do, improving your soil. You will still have some thisltles but they will be chopped with the grain or you can cover the remaining patches with cardboard or dig them out. NO ROUND UP NO NO NO
But nothing attracts worms as well as thistle in my clay. I try to keep the flowers from going to seed, but let the thistles run their course if I can.
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Canadian thistle has rhizomes. Even a tiny bit of that root left behind will regrow, forever and ever, and they're much too deep to effectively dig by hand. Conversely bullthistle is a biennial with a taproot, and all you need to do is sever the root a few inches below the surface.
Repeatedly plowing and turning the soil while it's very hot might dry out enough roots to be helpful, but you'll lose as much topsoil to wind as you'll kill thistle, so not the best course.
Roundup won't kill them entirely but it would give you a head start. Same with hand-digging what you can reach (and remember to pull as much root as you can get out). However R Scott's remark about pH gives me an idea... what if you saturated that patch of ground with sulfur, enough to turn it really acidic? would the thistle survive this abuse? might be worth testing the soil and trying sulfur on one little spot. As to what good shelterbelt trees would like that ground afterward, maybe spruce, and do remember it will run off somewhat into adjacent soil.
You'll definitely want a tree that hugs the ground at the bottom, tho (which spruce will do if not planted too close together) to starve any remaining thistle of light.
A number of plants produce toxins of their own to discourage competition, and some of these (including that from black walnut) are a whole lot more toxic than Roundup, and far more persistent in the soil (Roundup was developed specifically because a product was needed that broke down very fast and did not remain significantly toxic). I wouldn't worry too much about doing a spot application as needed.
Remember to plant your shelter belt as several staggered rows of trees, not too close together, or eventually they will thin out at the bottom and that kinda defeats the purpose, even if they don't kill each other competing for water. My aunt told me that they had to keep the grass plowed down in their shelter belt or it would kill the trees. She was up on the Teton bench, which is a bit south of and basically the same climate as yours. She had mostly Russian olive and carragana, which are both pretty tough.
yet another victim of Obsessive Weeding Disorder
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