Does anyone have experience with glycerin as an herbicide? I've been using it full strength and 50% with water on poison oak, and I've have great results for 1 season per treatment.

Not good results with blackberries.

I figure it's because the glycerin coats the leaves. Any other ideas why it works?

thanks
Louisa

I know if you dilute it enough it DOESN'T act as a herbicide. I dilute it about 75% water and throw it over the trees and brush in the woods next to my house to kill mosquitoes. As the soap runs off the leaves it gathers in the puddles and kills the eggs and larvae. It doesn't kill the trees and brush, though.

A lot of plant leaves have a waxy film that keeps the leaf from losing moisture: I suppose the soap, in a high enough concentration, could remove that film and cause the leaf to dehydrate, killing it.

It's not so effective on Perennials, but glycerin will sterilize the seeds of annuals, which includes most weeds. I've used if for 8 years to keep my fence line clear of weeds. I’ve only had that soil tested once, and there was no buildup of any compounds or metals. My soil pH is naturally very high (over 9.0), and the glycerin did not change that. The raw, undiluted glycerin still had all the soaps and some residual food particles, but no methanol, when I used it.
We have an organic nursery, and still use builders lime to keep the pH high enough in the rock banks to prevent (most) weeds from germinating. The glycerin has the advantage that it breaks down more quickly. If it isn’t reapplied annually, the weeds come back.

Cheers,
JohnO

quote:

Does anyone have experience with glycerin as an herbicide? I've been using it full strength and 50% with water on poison oak, and I've have great results for 1 season per treatment.

I also use it straight on poison ivy. I have had to go back and reapply it once again due to the rain washing it off the leaves. I think the oil suffocates the leaves and the plant dies.

I would love to use it to kill mosquitoes, but the frogs & bats need to eat something.

quote:

Does anyone have experience with glycerin as an herbicide? I've been using it full strength and 50% with water on poison oak, and I've have great results for 1 season per treatment.

The soap is a pretty good herbicide, maybe it is the soap and lye dissolved in the glycerin or maybe the three together.

I'm assuming you don't acidulate the glycerin.

Thanks for the responses! I haven't done anything special with the glycerin, just mixed it up with water, 50:50, and dumped it on the poison oak. I checked the poison oak yesterday and it's still dead after 5 months. Poison oak is a perennial, with slightly waxy leaves, so I'm surprised that it works so well. I'd like to know why it works on a biochemistry level...

Research is being done on using glycerin to kill parasitic nemotodes and mixed with nitrogen to make fertilizer .. there may be many ag applications for glycerin.

Louisa

This may seem like an off track response but it isn't in reality.

Look up "lye soap" on the net. It has long been a known fact that lye soap s a cure for poison ivy/oak/sumac. We discovered this as a fact also a couple years ago on the farm where there is plenty of the nasty stuff. While cleaning the disks on the tiller the operator regularly got dinged by it and used the soap I make from the BD glyc layer to get rid of it.

The reason is works so well is that it is the oils from these plants' leaves and stock that do the damage and our glyc soaps get right down in there and strip these oils out, even below the skin's surface a layer or two.

So, what may be taking place in the living plant is that it's oily lifeblood is being choked out by the mostly saponified biodiesel glycerine.As it conme sout of reaction it is already an excellent degreaser, although not yet fully saponified into full on soap, it is still sufficiently so to act on plants.

Anyway, that's my take on it.

I think Legal Eagle is right about why it works because.

At a place called Manly, they had an impressive stand of Norfolk Island pines. When the trees started to die the authorities investigated.
They found that detergent in drains that emptied into the ocean was being blown by the wind onto the trees and destroying the oily protective coating of the pine needles.