How to kill weeds at the base of immature and mature trees (with roundup) without harming the trees?

I've been told to simply put a board in front of the tree to catch the overspray. Or, wrap the base in poly.

Or, use a weed wick? How about a weed burner? ("Kill it with fire!")

What chemical are you spraying ?
And
What are the weeds you are trying to kill?

No botanist, but I wouldn't get roundup near the tree at all. I've seen it soak down with watering and get into the roots. I've either just dug up the weeds and/or placed black visqueen down and covered that up with some kind of mulch or rocks or something. Burning works too, but care must be taken to not get the bark, and it is not permanent. One thing I've considered trying but haven't yet is a mild salt solution. Enough to kill the weeds, but not strong enough to effect the tree.

When I'm trying to spray around delicate plants, I use a flat bladed shovel. Insert shovel between plant I want to keep and plant I want to kill, then spray. Be sure to keep the same side of the shovel turned towards you. A light mist is all it takes, go too heavy where it's dripping off and it might cause problems.

Roundup (the original Glyphosate formulation) is not absorbed by bark, only greenery so if you don't spray the leaves of the tree it will not affect it. Young, thin-barked trees may be susceptable.

This should be taken with a grain of salt as Monsanto has extended the name "Roundup" to multiple chemical formulations, not just the original Glyphosate, for marketing purposes. So READ THE LABEL and know what you are buying. This is important for any herbicide, insecticide, or fungicide you expose yourself to. I know it is boring and confusing. If you are uncertain about what you find on the label, do your research either on the 'net or (better) consult with your local extension agent.

A light coating is not going to hurt anything, but the weeds and grass. Most people put way more down than is needed. Follow mixing instructions too. If sapplings I would wait a couple of years. ymmv.

Use the proper mix ratio for the weeds you want to kill.
Don't spray on a windy day.
Adjust your spray nozzle properly; not a fine mist or a stream.
Enough to dampen the leaves of the plants you are killing.

It'll be rainfast between 1/2 an hour and 3 hours depending on how fast it dries which depends on temperature, humidity, wind, and sun exposure.

This is for glyphosphate.

This message has been edited. Last edited by: trapper189,

quote:

Originally posted by architect:
... Monsanto has extended the name "Roundup" to multiple chemical formulations, not just the original Glyphosate, for marketing purposes. So READ THE LABEL and know what you are buying. This is important for any herbicide, insecticide, or fungicide you expose yourself to. I know it is boring and confusing. If you are uncertain about what you find on the label, do your research either on the 'net or (better) consult with your local extension agent.

+1

For example, the white bottle of concentrate used to contain 20% glyphosphate, but now it contains:

Triclopyr, triethylamine salt ... 2.50%

Fluazifop-P-butyl ... 2.00%

Diquat dibromide ... 1.50%

Triclopyr works OK on broadleaves, but it works better on woody stemmed brush. Triclopyr and Fluazifop-P-butyl both have residual soil action (i.e. 30 days and 15 days respectively depending on conditions). I wouldn't want to get any Triclopyr on the bark of a tree.

If you switch to the gray bottle of Roundup with the 4 month preventer in it then it's even worse for trees. They add Imazapic ammonium salt to the other three, and it can be absorbed by tree roots and damage/kill trees. I follow a wildlife biologist on YouTube and some of the habitat work they do (i.e. getting rid of non-desirable trashy trees and leaving desirable trees like oaks) they always mention it can inadvertently kill oaks. Also, Imazapic ammonium salt is an herbicide used to kill trees by girdling (i.e. damage bark to cambium all 360 degrees around tree and spray herbicide on exposed area) and the same thing could occur if somebody was heavy handed with a weedeater (i.e. damage thinner barked trees) and then following up with this spray.

The OP is much better off going to Ace Hardware or Tractor Supply and buying 41% glyphosphate. It's a contact herbicide and doesn't have any residual soil impacts. Other posters have mentioned options for managing overspray (e.g. shovel as barrier).

---

Ego is the anesthesia that deadens the pain of stupidity

DISCLAIMER: These are the author's own personal views and do not represent the views of the author's employer.

As mentioned before, Roundup (Glyphosphate) works through the leaves and translocated down to the roots where it does its work. Plant needs to be active to get down to the roots (sunny warm day). The glyphospate is bound up by the soil and unless we are talking years of use should not make deep into the ground. Sunny warm day, no wind and just in case low pressure in your sprayer to reduce any drift. Glyphosphate kills just about all plants so if you want to keep the grass alive don't use it.

Weed B Gone is 2-4-D and will work on annuals (weeds). It has limited effect on perennials (trees and brush). It is absorbed through the leaves. It will knock back the current years growth on perennials but the plant will recover and live, very possibly sprout new growth later that year. Grapes are an exception to this. 2-4-D will absolutely kill grapes.

Brush-B-Gone is Garlon and this works on perennials (woody plants) and a lot of broadleaf weeds. Garlon is the name of the product, triclopyr is the chemical. It is also absorbed through the leaves and at full strength can be painted or sprayed on fresh cut stumps, but I don't know if it is absorbed through the bark. One thing I noticed with the Brush-B-Gone on poison oak the whole plant needs to be covered, if you miss part of it that part will live.

There are so many new chemicals out on the market I know nothing about, I just use these three. It has been so long since I bought any of these three (I bought BIG jars) it's possible that Roundup, Weed-B-Gone and Brush-B-Gone have new formulations.

I was a Consulting Rosarian for the American Rose Society for a number of years, routinely used Roundup and never lost a bush. Here's your pro tip:

You don't spray with glyphosate (or any other weed-killer) anywhere near specimen plants, you paint with it. Put the stuff in a little cup, and paint the weeds directly with the right sized brush (and yes, sometimes that right-sized brush is a Q-Tip) making sure not to drip on anything you care about.