Is it possible to mix roundup concentrate (360) with water based emulsion, 1:1, before I dilute? I ask because I'm looking to kill an entire garden's worth of scrub, weeds, brambles and low quality grass (on a building site) as part of the new landscaping, and I'm finding it hard to remember/see where I've been with the knapsack sprayer. There are also a couple of trees I'd like to keep so I plan to be careful around them and wash them down with clean water after, but it would be helpful to see if there is any overspray on the leaves. Wondering if normal water based emulsion is ok for use/won't denature the roundup

  • 2
    What are your plans, your goals? Roundup is only necessary after the fact...you are beginning with a new landscape. Roundup is NOT necessary at all. Think about this. Your soil is full of seed. There is no getting around that. Roundup sprayed on vigorously growing plants (not woody perennials just herbaceous perennials, annuals) will kill that plant right down to the roots. Meanwhile there are thousands of weed seed in the soil right beside this one plant. Roundup is not a pre emergent pesticide/herbicide...forget about killing plants to make your landscape.
    – stormy
    Jul 16, 2017 at 23:12
  • And hey, it has been awhile since I've read the instructions on Roundup or any glyphosate product. ONE TO ONE mixture for concentrate? Are you sure? More like an ounce per gallon...once you've sprayed, you have to wait at least 3 weeks for total kill and before you plant another plant or try to grow another seed.
    – stormy
    Jul 16, 2017 at 23:16
  • 1
    Actually it is 3 ounces per gallon. Not at all a one to one mix!! Do not spray when there is even the slightest breeze. Keep you wand down near the ground! Keep the spray head making large droplets not fine mist. You know, I never use this stuff except for driveways of gravel. What are your plans, goals? Your project sounds interesting. I would STOP spraying right now. Weeds are NOT the big deal everyone makes them out to be! Weeds and all organic matter ADD organic matter to the soil. Let's talk about the availability of certain mulches. Primarily human poo plus sawdust...
    – stormy
    Jul 16, 2017 at 23:22
  • Well, it was the paint I was after mixing on say a 1:1.. I mix the roundup at 2.5% with water, and I was thinking to chuck some amount of white paint in there too, so that I could see where I'd sprayed.. As per the Q, it's a building site, an area of land that will one day be the garden but right now is just a mishmash of grass (not particularly nice grass either - all different sizes, shapes and colours), weed, brambles and everything else you'd see on a patch of land neglected by anything for 15+ years..
    – Caius Jard
    Jul 17, 2017 at 11:22
  • Re the plans/goals: I'd received advice to kill it all off, scrape the topsoil into a pile with the digger, set the levels of everything with whatever old crap I can find, and then layer the topsoil back out again. The only thing I really want to keep are the fruit trees planted 4 years ago, and the established mature trees (30+ years old, I think I'll struggle to kill em with Glypho).. I sprayed with a low pressure, trying to avoid misting and keeping the wand a few inches above the ground, then went back with the hosepipe and washed all the fruit trees down all over.. Hope i got it right!
    – Caius Jard
    Jul 17, 2017 at 11:25

2 Answers 2


Don't use paint! Any paint has binders and adhesives, so it will tend to clog your sprayer, and (as you note) you can't be sure what the interaction of the various ingredients will be with the active ingredients in your weed killer. Besides which, very little of paint is actually dye or pigment.

There are a number of dyes designed specifically for mixing with weed controls to help you see where the spray has gone. For example, Mark-It Blue.

  • You are so right on the money. Paint would clog up his sprayer within minutes!
    – stormy
    Jul 16, 2017 at 23:07

There are a few issues with using paint:

  1. Would take some balancing to get enough paint to be visible, but not so much that it would interfere with the operation of the sprayer. I'd suggest starting by making a dilution of paint at 1:4 with water. Obviously you need to use latex paint. Just use the paint alone, and continue to dilute until you have a just visible cover. (Of course this could be used for 'instant greening' with the choice of a suitable paint. Cheaper than green outdoor carpet...)

  2. You need to really clean out the sprayer after. Dried paint can be difficult. Cover the nozzle if you stop for even a few minutes, as it has maximum exposure to air, and minimum hole size. An aluminum foil cap works well.

So much for the mechanical aspects.

Glyphosate deactivates on contact with clay. Paint pigment is fine particles. Depending on the particular pigment used, they may function as a de-acativator.

Paint has a bunch of ingredients in it that may react with the ingredients in the weed killer.

Baler twine is another method for tracking where you've been. Put a line along the property every 10 feet. Maintaining a consistent distance for 1 or 2 passes on either side of a line is fairly easy to do. Baling twine is cheap, and is available at any farm store.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.