I have a friend with a small yard in a city neighborhood. They have some flower and rock beds that have been overrun with thistle. We tried using a mixture of apple vinegar, dawn, and salt. It made a small dent but did not really kill them. She has also tried finding someone locally with goats, but has not had much success with this.
Does anyone have any good ideas for organic or non-poisonous applications that are effective on thistle?
Decompaction. You have to progress through to more fertile soil. Chop and drop the thistles where they are to get the minerals they are mining into the topsoil. You can add rock dust to get mineral levels up faster. You can broad fork and/or plant daikon to loosen the soil.
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I could be wrong but you could chop them up and over seed with dandelion, queen anne's lace, or daikon radish. These are all tap rooted and I often find them among the same places where the thistle, burdock and other nasty tap rooted "weeds" are growing. Bees like thistle, but barefoot kids do not.
When attacking thistles it seems to work well if you can get the root system. Spraying/hoeing will leave the root system to grow back.
Also the best line of attack seems to depend on the thistle species - we seem to have taprooted bull thistle. Creeping Canadian thistle is another beast entirely - it sends runners out so attacking the main plant won't destroy the system of roots.
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I agree with decompaction and removing the entire thistle root.
When you say "rock", do you mean largeish ones, or pebbly 'rock mulch'?
If they're large, that's simple. If it's mulch, it's a total pain!
Assuming it's rocks, I'd:
take up the rocks and
decide which plants can be dug and replaced, need to be left, etc
fork the area over, removing all thistle roots
Spread chipped tree mulch/bark mulch thickly (at least three inches)
Nestle rocks naturalistically back into mulch
dig into native soil and replant
I strongly suggest avoiding salt- it moves freely through the soil and is very hard on desirable as well as weed plants.
R Scott wrote:Decompaction. You have to progress through to more fertile soil.
I totally agree with this. Since it's a small lot and there are flowers in that spot, I'd recommend making a raised bed right over the thistles, could be made of wood to make it neat. Fill the raised bed with good soil and compost and plant it with flowers. Those compact soil loving weeds will hate it.
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