You could try to freeze your vinegar to just 30-32 degrees and remove the water ice crystals.
Acetic acid doesn't freeze until about 28 degrees.
This may help concentrate it somewhat.

(but both reach the boiling point at about the same temp so you can't distill it that way.)

I wonder how burning the soil system with highly acidic vinegar compares in friendliness to using a relatively inactive herbicide like glyphosate.

I wouldn't exactly consider a high concentrate acid solution necessarily "earth-friendly".....not unless you consider a scorched earth policy friendly :-) Seriously, while a high concentration natural acid like citric or acetic acid IS effective against some stubborn weeds and is considered "organic", it can also do some significant and long lasting damage to the soil - it alters the pH so radically it is difficult and time-consuming to restablish pH and it effectively destroys any soil organisms in the process. Not to mention the stuff is extremely caustic and should be handled and used with extreme care. 'Organic' does not necessarily mean safe to either you or the environment, only that it is derived from natural products

"Blackberry and Brush Blocker" by manufactured by Greenergy Inc. is the stuff that Ann Lovejoy raved about a few years ago. Due to EPA labelling requirements regarding the classification of pesticides, its active ingredient is listed as a 20% citric acid base - it does contain acetic acid (vinegar) but only at 7% and this is included under the heading of "inert" ingredients. But both acids are byproducts of the wine industry.

Most garden centers have stopped selling the stuff.....I am assuming primarily because the demand has dropped since the initial hoo-haa about the product but perhaps also because it is rather dangerous and with longlasting implications. Use at your own risk :-)

AFAIK, McLendon's still carries it.

All good inputs. I perused some extension service articles after reading these; I hadn't realized that 20%-acidity was so dangerous (okay, so Chemistry wasn't my favorite class)! If I decide to bump the 5% up a bit, I DO like the idea of freezing, and would probably go that route.

Gardengal, I'm interested in these long-term effects. Understand that, thus far, all of I've read were about half a dozen extension office articles linked off the Organic Gardening forum; I'm sure there are a lot more, hopefully more recent, out there! One article stated that "acetic acid is not reported to accumulate in the environment and readily breaks down to water. Interestingly, 24 percent acetic acid apparently can temporarily decrease soil pH". Source: http://www.ag.ndsu.nodak.edu/aginfo/entomology/ndsucpr/Years/2002/July/18/weeds_18July02.htm That article was about a half-dozen years old, which, in this day and age, is ancient history, possibly folklore!

I also found reference to the labeling you mentioned on one of the products. Per the attached, apparently calling acetic acid 'inactive' gets the mfr. around some regulations. http://oregonstate.edu/dept/nursery-weeds/weedspeciespage/acetic_acid_factsheet.pdf It does tell me something that they only used the vinegar at a lower-level (albeit still higher than 5%).

Types of places I'd be using this: aisles in veggy raised gardens (already have cardboard and hogfuel down), between concrete sections of sidewalk,on gravel path.

Many thanks (among other reasons, for keeping me from burning out my eyes)!!

Plants thrive on vinegar when it's wet. If you want to kill with vinegar it's gotta be hot and dry. Big money waster if not used correctly.

Horticultural vinegar acts as a herbicide in two ways - spraying it on existing weeds, it acts as a dessicant, drying or burning foliage due to the acid content and does need warmer, sunny weather to accomplish this rapidly. It can act in cooler, gray weather (acid is acid) but may take longer and any impending rain or irrigation will rapidly dilute it and wash it away.

The second method is when used as a soil drench to kill persistent weeds like blackberry vines, horsetails and brush, it alters the soil pH by lowering it to the point where plants won't/can't grow. How long this lasts depends a lot on soil conditions and the amount of moisture present, but it doesn't dissipate rapidly and the effect can last from several months to a year. Meanwhile, the soil is acidic enough that virtually nothing will grow and even attempting to remediate the effects by liming or other amendments will not work in a short period immediately, either. And such an overly acidic soil either destroys all the microfauna or retards their populations to a substantial degree. And that healthy, biologically active soil is even harder to re-establish.

Personally, I believe using it for something like the weeds that form in the cracks of driveways or other paved areas is its ideal usage. I'd avoid using it as soil drench whenever possible and I'd be very cautious when using as a foliar spray to make sure it is on the foliage and nothing else and that you don't get any drift or overspray to more valuable plants.

Okay, this is all making a lot of sense. The 5% stuff worked well on the baby weeds that are popping up, but I shouldn't try to ramp it up to taken on the big boys.

Now, when I do encounter one of the weeds from hell (and, living on 5 acres, that's a given), is the Greenergy product you mentioned the best option? If so, I assume that 20% citric acid is significantly less nasty than 20% acetic acid? Types of undesirables I'm thinking about are the blackberries that the birds bring in, grass clumps that lurking under the cardboard and hogfuel in the garden area, and buttercups.

Sorry for all the questions. After deciding to put in a veggy garden, I'm trying not to use any of the really 'nasty stuff'. Meanwhile, as this thread is such a clear example, sometimes what is being passed off as a 'natural, organic product' isn't really the right thing to use!

Many thanks!

Going against the grain but a reliable weed killer is glysophate. I've used it for years and my pets have lived longer than average. Science supports it's use because they can't come up with anything bad other than the founder, monsanto.

Vinegar, like ALL garden products, needs to be used in the right amounts! The idea is not to contaminate the soil, but to apply just enough to cover the leaves of an unwanted plant. For weeds between pavers, I would suggest plain boiling water instead.

I bought some horticultural vinegar under the Scott's label, but I believe Safer's also sells it. Most garden centres should have one or the other.

Safer's weed control products are not vinegar-based. And I think we need to be careful about labeling vinegar as a "garden product". It is not. The fact that it can have herbicidal properties does not necessarily ensure that it is approved and registered for that use.

Cheryl, to answer your question, the citric acid/acetic acid product (Greenergy) has the same effectiveness as the straight 20% vinegar products - citric acid works in a similar fashion but its inclusion as the primary ingredient gets around the EPA labeling conflicts. Unfortunately, to rid blackberries, this does need to be applied as a soil drench - spraying just the foliage will have virtually no effect. The same with horsetails. I realize it's a lot of work, but grubbing them out manually is truly the most efficient control. And try to catch them when they're young - much easier to remove than when they become well rooted and established. The birds 'plant' them in my garden as well:-)

Here is a link that might be useful: fact sheet on acetic acid