a: Scything appears to be a great alternative to the brush clearing I do with a 6 hp DR trimmer, but I want to know if there are scythes that will clear heavier brush like blackberry and vine brambles like wisteria, kudzu and English ivy overgrowth, even saplings, etc. where the growth is not a consistent grass but general mixtures of high weeds.
b: Clearly, I consider the physical aspect a full body exercise, but would hacking through heavy, high weeds and vine tangles be excessively tiring even though I had good technique?
c: And, Is scything effective if I were to top off vining ground cover, for fresh growth, without keeping the blade on the ground, which appears to be consistent methodology in videos.
Answer to a: Sounds like you could use some goats!
If you don't have any (and can't rent any), yes, blackberry brambles can be easily mowed with my light bush blade. Individual, softwood saplings, like aspen and pine, up to the diameter of your little finger, can also be easily mowed with short, quick, trimming strokes, at a shearing angle. A bush blade is still a scythe blade, not a hatchet! It cuts at a shearing angle, not with a direct chop like a hatchet or machette. Hardwood saplings up to 3/8 in diameter, can also be easily cut with my light bush blade. However, when I am mowing a brushy area, while I mainly use my light bush blade, I also take a pruning saw with me in a belt holster. If the scythe doesn't cut something easily, I take out my Silky pruning saw, and saw the sapling off, flush with the ground. My light bush blade is short, stiff, and tough, but it is not an axe, and a snath is not an axe handle. It has it's limits, and I don't push it. If you need to mow a lot of big weeds mixed with woody plants and trees, you might want to have a couple of other tools on your belt, like a small pruning saw, and a pair of loppers, depending on your skill with a scythe.
I've never used a DR trimmer, but when I see what they cut with it on the TV commercials, I just laugh. It looks so noisy, polluting, heavy, expensive, and cumbersome, pushing one around looks like so much more work than using a light scythe. Less fun anyway. I bet that I could easily beat it with my scythe. In any case, I would prefer a scythe.
Answer to c: You need to keep the blade flat on the ground when mowing a large area of grass. Grass is bendy, and it bends away from the blade the least, when you cut it down at it's base. Otherwise, it's very easy to top off weeds. I can even top off the individual seed heads of timothy grass, with my scythe blade. Doing that to a whole field would, of course, be a lot of work. Weeds with stiffer stems are pretty easy to cut at any height. With some giant weeds like burdock, you have to cut the big leaves and the tops off, in order to access the stem at the base. But once you can access the thick, tough, 2 inch+ base of a mature burdock plant, a scythe blade won't be able to cut through it. So I pull out my pruning saw, and saw it off flush with the ground.
Answer to b: Modern people are so removed from handtools, that they seem to either expect a scythe to be an indestructible weed whacker, that somehow always stays sharp, and just about does all the work for you, or they expect to re-create by hand, the excessive need for power of a power tool. A scythe requires more precision, than power, to use it as it is designed. With a scythe, yes, you will get a lot of exercise, and yes, you will have to learn new skills, and you will have to take care of your tool and keep it sharp, and your results will depend on your how much you apply yourself to becoming proficient with the tool.
On my to-do list is to make a video of how to mow a bramble patch with my 50cm light bush blade. Until then, here are two videos for comparison. Above, "Scyther of the Decade", Niels Johansson, is peacefully mowing some tall weeds with a very short 35cm Hahnsense blade, that he sells. Probably more of a ditch blade, a little lighter than a light bush blade. He mows with dexterity and precision. To me it looks like he is creating a clean pathway, and mowing the stems very close to the ground so as not to create sharp, poky, (and dangerous, if woody), stubble. He also has rocks to contend with by the sound of it, so he is mowing carefully to prevent damage to the edge of his blade. If he didn't care how neat the area looked, he could use a longer blade, and hold it up a few inches off the ground (so the blade would move above the rocks), and take longer strokes, and quickly cut down the whole area.
Below is a DR Trimmer in action. "Urgh, urgh, urgh! More POWER!" For the first minute they mow tall grass, in the video. At 1:11 the guy is mowing some weeds similar to what Niels was mowing, I think. Oh, the NOISE!!! And what a mess! And then they say, "It looks like a park." Two guys with scythes could have made that park look beautiful in a couple of hours. I know with which tool I prefer to spend my time outdoors with, but to each his own.