From experience, thistle will pop up through landscape fabric with no problem. A tiny missed piece of root will become a new plant -- or a new colony. A friend told me about an extension service experiment where they enclosed a one inch piece of root inside a 120 gallon black plastic tub of soil -- no light, no holes for water to get in (although it must not have been bone dry soil), and they figured the black plastic would heat up in the sun and kill anything inside. One year later, they opened the container, and it was filled with thistle roots. I applaud your dedication to using organic methods, but I had to resort to chemical warfare... and ordinary weed killer did nothing. Brush killer works but can take several applications. I have a weed torch that I use in some areas, and that has worked on thistle, but it often regrows a few times before giving up.

Good to know Jill. My weed warfare is not organic by any means. I was hoping to use landscape fabric as an extra layer to my efforts.

I'm working on it systemically by using a solution of water with a little bleach and dish soap in a hand spray bottle. Wearing protective gear from head to toe, I first cut the plant stem down to just an inch or so above the ground. Then, with the spray nozzle set to stream, I physicallly place the tip of the spray nozzle directly on to the cut stem and then spray, soaking them well. I do not spray until that nozzle is touching the cut stem. This method keeps the solution from spraying on any nearby plants and soil.

WARNING!!: BE SMART & CAREFUL!! This method warrants precautions just as any other commercial chemical products do. The solution will irritate, even burn the skin, so chemical gloves and covering all skin that can be covered is a must!! Also remember what bleach does to fabrics. Wear old clothes and an appropriate apron, if you wish. Refills do get messy and wasteful from bubbling over. Like a high school chem lab experiment. Be sure to use up all of the solution and rinse the bottle and sprayer when your done. Unused solution will not store because the built up pressure will eventually break the spray nozzle cap. Don't ask... So if I think I have treated all the thistle there is to treat, I turn to the dandelion plants (because I actually view dandelions as weeds ) Works like nobody's business. JUST BE CAREFUL, BE CAREFUL, BE CAREFUL!! .....AND SMART ABOUT IT. (Disclaimer, I shall not be held liable for, but not limited to, any bodily injury or damage to any property, etc.)

This treatment was successful in erradicating a berry patch we inherited on our property, when we bought our home, and as subsequent runners showed up after treating and digging up the dead roots, I would treat them. It was effective with persistence, so I figured the same strategy might be the best possible option that I know of to use on this plant. I grow organically, but I get too impatient with weed control. If only the neighbor would cut theirs before flowering and seeding and/or take steps to eliminate them altogether. They are new neighbors and a bit younger. They are very nice, but it's still a delicate balance.

You can limit overspray by applying herbicide with a gloved hand. Dip your hand, then "pet" the plant you're trying to eliminate. You still need to be sure the plant won't sway in the breeze and contact other plants, but you can take care of that by breaking off most of the plant and wetting the rest of it with herbicide.

I forgot to mention above that I first cut the plant down to just an inch or so above the ground and be sure there are no leaves left. Then I literally put the spray tip on the cut, stubbed stem. With the spray nozzle set to stream so it goes nowhere beyond the stem, and trust me, I wear protective gear from top to bottom.

NOTE: I edited that post https://garden.org/thread/view... to include this information in more detail, to keep it all in one spot.

Thanks... I'll try your bleach method on some other persistent things as well!

You're welcome. I'll be going out there soon to see how it's working. My first spraying was this past Thursday.

I hate the idea to be using such drastic chemical measures, but I do my best to respect nature. I'm afraid it would drip from my finger on to the soil before reaching the stem, even close up. My afore mentioned method, as it were, controls the possibility of drips pretty well bc I don't spray until contact with the stem.

I either need to use chemicals on certain weeds or have a much younger and more capable body!

It began with the berry patch in 2012. I was younger and more capable, but there is a breaking point that leads to desperation when the plant doesn't give in.

WARNING!: BE SMART & CAREFUL!! This method warrants precautions just as any other commercial chemical products do. The solution will irritate, even burn the skin, so chemical gloves and covering all skin that can be covered is a must!! Also remember what bleach does to fabrics. Wear old clothes and an appropriate apron, if you wish. Refills do get messy and wasteful from bubbling over. Like a high school chem lab experiment. Be sure to use up all of the solution and rinse the bottle and sprayer when your done. Unused solution will not store because the built up pressure will eventually break the spray nozzle cap. Don't ask... So if I think I have treated all the thistle there is to treat, I turn to the dandelion plants (because I actually view dandelions as weeds ) Works like nobody's business. JUST BE CAREFUL, BE CAREFUL, BE CAREFUL!! .....AND SMART ABOUT IT. (Disclaimer, I shall not be held liable for, but not limited to, any bodily injury or damage to any property, etc.)

Probably not the best method, but desperate times call for desperate measures, and it delivers.....with persistence. Hopefully, that will be the case for this plant. Works real well on dandelions, but I don't make it specifically for dandelions. Only for stubborn, persistent plants that are not affected by weed killer. I use it up on dandelions and other weeds using the same method.....set the spray on stream, and contact the plant with the nozzle before spraying.

Might be worth a try to ingratiate yourself with the neighbors and volunteer to cut off the thistle heads before they blow. We're being invaded by Italian thistle (Carduus pycnocephalus) here in coastal California and no one seems to be resisting . My next door neighbors let me try to control them in their backyard but it's a rearguard losing battle since the wild areas are being overrun and the wind carries them far and wide. The farm boy in me hates them, but I'll soon be too old to fight.

I just might do that.

Update: The bleach treatment is working, even on plants that have grown large, but they're still popping up in other areas. This will be a long, long battle.