Are these things effective? I'm looking for something to help clear up growth along fence lines, and undergrowth in some patches of trees and woods. Crap like vines, thick grass, ragweed, etc.

I have two gas trimmers already, one with a string head and one with a metal blade head, but curious if these big trimmers are more effective on heavy weeds and vines.

I've only had one, and imo, based off of the one I had, no they aren't worth it in your scenario. The only real benefit was it was good at staying level for a nice even cut, but mine was woefully underpowered compared to the string trimmers, and changing the string was much more of a chore. But it does save the back if you've got a long fence line.

I have the commercial grade model that DR Trimmer Mower makes. I use it a lot at the ranch. Has a Kawasaki engine and not underpowered.
It is great along fence lines. I bought it for doing light brush and heavy weeds and grass.
The main advantage is that you can use very heavy cutting line on it. On mine I can use line that is 3/16. This works great for woody stems etc. It will cut light brush and heavy pasture weeds very well.
So it's good around field fencing, bar ditches,
stuff around rocks etc. It does good just mowing in rocky ground and is much faster and easier, in my opinion, than swinging a large weed eater in some applications.
It has its place for sure. I use mine quite often. It will do things a weed eater won't and vice versa.
It has worked well for me.

They are effective. My dad gave me his DR when he got a newer model and it's been going 20+ years.

For thicker stalks and such it might have a problem. The type with a disc that can take down saplings might work better but that thick trimming cord does pretty good for lots of stuff

If you've got rocks growing up out of the ground as we seem to have here in our area they don't works so well. Constantly hitting rocks with the wheels and throwing the machine up, down, sideways. We had one but sold it as it was more work than a regular 2 cycle gas trimmer. A couple of goats appear to be the best method here.

Always the herbicide option.

MouthBQ98 said:

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Are these things effective? I'm looking for something to help clear up growth along fence lines, and undergrowth in some patches of trees and woods. Crap like vines, thick grass, ragweed, etc.

I have two gas trimmers already, one with a string head and one with a metal blade head, but curious if these big trimmers are more effective on heavy weeds and vines.

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I've used a cub cadet string trimmer for several years and it works great with tall and thick grass. Should handle ragweed no problem. I haven't used it on vines, so can't specifically comment there.

I've had mine since late 2019/early 2020 and have had no maintenance issues with it to date.

Ranch Dressing said:

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MouthBQ98 said:

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Are these things effective? I'm looking for something to help clear up growth along fence lines, and undergrowth in some patches of trees and woods. Crap like vines, thick grass, ragweed, etc.

I have two gas trimmers already, one with a string head and one with a metal blade head, but curious if these big trimmers are more effective on heavy weeds and vines.

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I've used a cub cadet string trimmer for several years and it works great with tall and thick grass. Should handle ragweed no problem. I haven't used it on vines, so can't specifically comment there.

I've had mine since late 2019/early 2020 and have had no maintenance issues with it to date.

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2nd for the Cub Cadet. I've been very pleased with mine.

Funky Winkerbean said:

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Always the herbicide option.

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I agree. Some of that stuff on the fenceline will be easier to clear after it's good and dead and allowed to dry out in the hot Texas summer sun.

To add -- I also had a fenceline that hadn't been maintained in years and was covered with 2" thick woody vines and all manner of other brush.

I figured I'd buy one of those special string trimmers with the saw-toothed brush buster blade on it and go to work. After about 15 minutes of getting no place fast (and hitting metal t-posts with the blade), I realized that I'd have to make a half-time adjustment.

So, if OP can find a couple of guys who grew up using machetes to clear brush (i.e. - probably won't be anyone born in this country) give them a couple of good, sharp machetes. Show them the fenceline you want cleared and make a deal for a flat rate to clear the whole damn thing, with a promise of a chest of iced-down beer at the end and payment in cash.

Machetes in the hands of a couple of motivated guys who know how to use them will put to shame any walk-behind string trimmer you can buy.

Now, after you get the initial clearing done, maybe you buy yourself a string trimmer to keep it clear, or just have a yearly herbicide program using a residual like Imazapyr.

Just my two cents from somebody's who has been there.