Something changes (evaporation, breakdown?) and it loses its toxicity to plants rather quickly. Regular Round Up is NOT long term weed control.

That said, like all chemicals, don't go spraying your drinking or any water with it. I believe fish and amphibians hate the stuff. Don't go coating your pillow cases or socks in the stuff. It is not good for you.

ive been doing it for a decade and a half... no problem ...

it think it would be more along the lines of becoming inert.. rather than washing off ...

and of course... that is custom blended to the specific application.. rather than buying premix stuff ... in other words... rather low %

with your sprayer.. learn to adjust the tip to droplet size .... thru wand tip adjustment.. and low tank pressure ... and you can reduce overspray and drift SIGNIFICANTLY .... practice with water... on the driveway ...

ken

Active ingredient glyphosate is rendered inert in soil. I'd be lying if I
told you exactly what the chemical breakdown process is on woody substrate, but, as Ken assures you, and as I will second in a big way, you needn't have any concern about any roundup (glyphosate) which due to overspray ends up on soil, woodchips, or what have you. It will not hurt anything.

The one caveat, which toronado has already mentioned, is in aquatic situations. It's not the active ingredient per se, but the surfactant in the pesticide that really wreaks havoc on fish and amphibians. That is why preparations of glyphosate for use in wetlands, etc. lack the surfactant. But I don't think that's anything you need be concerned with at this time.

It seems many pesticide products can have problems with active ingredients not on the label being present. Also there was a chapter in Carl E Whitcomb's Establishment and Maintenance of Landscape Plants where specific instances were described involving damage or death to tree plantings following applications of glyphosate to the site, where the tops of the trees were not sprayed. Whitcomb said it would appear that they picked glyphosate up through the roots, I wonder as well about non-label active ingredients being present in the formulations used.

http://drcarlwhitcomb.com/

Tom, I live in a wetland area and am concerned for my frogs when I use glycosphate. Where can I find the aquatic formulation for sale?

Re: glyphosate picked up through tree roots.

Definitely a possibility, but generally only when certain circumstances occur.

If you are spraying over tree roots, verify that there are no suckers present. I've seen suckering trees killed by attempts at weed control when a number of suckers are present (in the lawn around the tree).

Don't spray if the roots are damaged. Even weeding, that could damage small roots, might contribute to the increase in potential for damage.

And, the BIGGIE is don't mix too strong. Normal recommended concentrations are extremely unlikely to cause damage to larger trees, from ground applications when the two situations described above are not present. However, it's not even uncommon to see damage (stunted growth, stunted foliage, and even tree death) when heavy concentrations are applied and soil surface is saturated.

The instances reported by Whitcomb have no explanations that fit conveniently with the dogma that glyphosate absolutely only affects parts on which it is sprayed directly, with no other mode of action ever occurring.

The only thing he comes up with is that it somehow traveled from the substantial roots of the perennial weeds it was being sprayed on into the trees.

The stuff is dangerous to wildlife and should be banned. At one time everyone thought DDT was safe too

j0nd, if you have a horticultural supply house in your area, ask for the aquatic version of glyphosate. I can't give you a name as there are numerous generic versions-even of the aquatic formulation-on the market now. But the guys at the counter will know what you need.

Long ago, I was at an arborist's workshop where one of the instructors warned not to spray Roundup
(or its generic equivalents) on the trunks of mature trees-which BTW have dead bark on the outside-on very warm and humid days. The thinking was that in such weather, minute cracks and fissures in the bark can open up, things you can't really even see, but which would presumably allow the active ingredient to make contact with green, photosynthetic tissue/cambium. I believe that, but this is not what was asked here. If one cannot spray glyphosate such that the overspray hits woodchip mulch...I would have discovered this 30 years ago.

See what I'm saying there? Of course there are exceptions to everything, but OP wonders if it is okay for overspray to hit the mulch, and the answer is a resounding YES...I have done it thousands of times-no exaggeration. Let's not muck up simple, objective fact with every conceivable-but highly unlikely-circumstance.

As to the alleged danger of using this product in this way, there is a great deal of paranoia and overreaction going on right now. I could kill myself with nothing more than tap water right now if I wanted to. Doesn't mean there's no legitimate use of tap water.

Joe, do you have a preferred weedKILLER? my idea is farmers spraying thousands of acres worth of round up create any issues. The couple quarts I might use a year are not an issue.

Rather like the brake cleaner I spray. Me and professional mechanics aren't dying from the stuff. However if some nut goes and uses a trailer load all in one day..

My understanding is that glyphosate binds tightly with soil particles (esp clay) and organic matter, which would include mulch. Having said that, I believe that it is possible (and I believe I have observed trees damaged in this way) for glyphosate to be absorbed by roots that are in/under the mulch when the mulch is moist and the spray is heavy enough to allow it to move into the mulch and come in direct contact with the tree's roots. Brandon alluded to this in his post above.

Be careful if you have live oaks.

I use a lot of woodchips in my garden on ten acres and never had a problem with glysophate over spray on bark.

Mike

Tom, I agree that when glyphosate is applied correctly per the label it is generally “safe” to use around trees. I’ve used glyphosate in mulch rings around trees for many years myself. But I think a note of caution is in order, because direct contact to absorbing roots or thin bark (as a result of overspray or drift) can definitely cause damage to young trees. Inexperienced applicators should be advised to be careful around their young trees (and other desirable plants).

It should also be noted that some products for homeowner use contain glyphosate in combination with other herbicides, and these would have even greater potential to cause harm to trees. As they say, always read the label carefully! A case where the wrong glyphosate product was used around trees (by a homeowner) was cited by one of the speakers in a recent conference I attended.

Of course-the label is there to be read.........and of all things, followed! This single factor may be the biggest issue in homeowner use of pesticides, the stubborn refusal to simply follow label directions. All of the issues you describe Dave are contained within that label. So read! Everybody!

There is a gap between experienced practitioners and newbie homeowners or what have you...and that can lead to the frustration of folks like myself who have accepted for decades that that which the OP asks about is OK. But with all pesticides....if label directions are followed-I know, what a concept-then results should be in the range of acceptable. If directions are not followed, then the sky's the limit for bad things happening.

So, for the record, glyphosate, the active ingredient in Roundup herbicide and all of its many generic equivalents, is absorbed through green, photosynthetic tissues-wherever they occur on the plant. So, if the plant in question is a tree sapling, still with its juvenile photosynthesizing bark, getting the material on that bark will have a very deleterious effect on the plant, all the way up to and including whole plant death. That's what herbicides do. So too with exposed roots: They may be old roots covered with dead outer bark, in which case no green tissues would be exposed. But one cannot always tell if there are or are not little cracks and fissures in this bark, leading to direct access to the cambium (green stuff) within. Therefore, yes, all applicators of this material need to be aware of this. I've also heard that certain genera of trees have greater sensitivity to trace amounts of glyphosate. American elm is one such species, although very few of us will ever be working around American elm, sadly.