[Pelican]

I've got thistles in one of my own landscape beds that are out of control! We can hardly pull them fast enough, a few days after cleaning the bed of them we have 4" high growth. I don't know where they came from, the bed that is 4' away from this one doesn't have them and uses the same mulch as this one.

Is there a chemical that will take care of them without harming my other plants? I've got arborvitae, rhododendron, azalea and spirea in this bed.

Thanks!

[Dot Pecson]

Hi Pelican,
I'm not sure I can help with how to get rid of those thistles... but I have a guess where they might all be coming from.

Bird feeders! It's pretty common for folks to get one of those thistle feeders to lure in Goldfinches and other seed-eaters.

So your culprits are most likely... birds. Yeah, I know. That's not much help, is it?
Dot

Dot

[Greensmith]

Thistle is easy to kill with roundup. A Lesco rep gave me a good tip, step on the thistle to break the stem than spray it with roundup.

I have seen contact wands in AMLEO that might help in tight areas of flower beds.

[Pelican]

How sensitive are the plants I listed to roundup? These things are all over, like a crop.

[spiderlily]

I have reclaimed 11 acres of perennial and shrub beds that had become a thistle field...

All those plants are sensitive to Roundup. Any leaf you touch with Roundup will show Roundup damage.

My way: With dampish soil, pull every thistle up from the root. When it resprouts, apply Roundup while it is still basal, before the thistle gets tall enough to be in other plants.

I also do not find thistle to be easy to kill with Round up--usually takes 2-3 applications.

[Mac]

Ive been using lesco prosecutor (swift acting specifically) for all my bed maintenance apps and find it gives great results on thistles in as little as a day. Its mixed at the higher end of the recomended rate but Ive actually had clients call to say the are amazed at how quickly their weeds dies. In a densely planted bed, I would not be really happy but I would follow spiderlily's advice unless the thistles can be bent into a clear mulched area. Standard practice here is to bend all weeds that are growing through shrubs, etc into a clear mulch area and then spray... I dont think pulling is an effective use of our time or their money.

[Terre]

I've used roundup on beds with those in it, but I apply it with a small paintbrush on the leaves. Also have found that an application of something like Preen helps prevent the seeds from sprouting.

[Forge]

You can use something like Weed-B-Gon that will not have AS MUCH of an effect on those plants listed as would an indiscriminate killer like Roundup if they happen to get some drift. But it still likely show some damage.

If they are Canadian Thistle, I would take the time to pull the large ones up by hand, (they come out pretty easy), spray any that haven't bolted yet and then apply Casoron to prevent new ones, especially if a birdfeeder is the source.

[Greensmith]

You mean to tell me that thistle seed in the feeders is actually canadian thistle? No wonder some of my clients have it so bad for no good reason.

[Mark Oomkes]

I would assume we are talking about Canadian thistle?

It's going to take a little work, spiderlily has some good recommendations.

I would also highly recommend Finale instead of Roundup, even the latest formulations. We are about the only 'scaper that uses it, but it works great for us. We even get some control of horsetail with it. It works fast, but still gets into the roots to kill it.

You could also try Dyclomec, since the plants you have listed are woody. If you have any perennials, don't use it. This is like Preen but quite a bit stronger, it will even control grasses, but you're still going to have to clean the bed out.

[Dale Wiley]

Thistle seed in bird feed is niger thistle.

It is NOT Canadian thistle. Very few states would allow a noxious weed to be present in bird seed mixes and be sold.

Canadian thistle is a hardy perennial wed that is very difficult to eliminate.

The advice about pulling them is good, as is the breaking the stem and applying the herbicide. In spot spray situations, I use Cross bow on them. They have a very waxy leaf and it is hard for any chemical to penetrate. Crossbow being a petroleum base works well there.

You best bet is to get them in basal or rosette stage with a 2-4-D or Crossbow mix. Glyphosate / Roundup is diluted by the excessive amounts of moisture in the weed and becomes pretty ineffective.