Typical plants (including most weeds) have green leaves and stems. That color of light is reflected, while others are absorbed. Some of the absorbed colors contain energy that the plant is able to tap, to power the chemical reactions that keep the plant alive.

Most other green things also are green because they reflect that color and absorb other colors. Well, suppose we spray-painted a weed with green paint? The PAINT would absorb the colors that the plant needs, in order to survive! So, after a week or two of the plant being in the dark, despite broad daylight, it will die. It may die even faster if the paint blocks its respiration pores.

Now all we need is a non-toxic paint. I have linked a suggestion. Simply check the weather before applying so that it can dry before getting rained on. This particular substance will gradually wash away in the rain, but it takes rather longer for that to happen after it dries.
-- Vernon, Jul 11 2015

Something non-toxic that should stick Colored_20School_20Glue
If colored green, it won't be obvious that the weed is getting killed [Vernon, Jul 11 2015]

Hard to believe but they made my green weeding robot! http://makezine.com...ered-weeding-robot/
[pashute, Jul 14 2015]

No really, this is too much! http://www.enviroga...ding-robot-concept/
[pashute, Jul 14 2015]

The problem with this is that you would have to cover the entire weed. Also, most weeds will recover even if you cut off everything above the ground, so it's unlikely that this would work.

Most weeds can be destroyed if you cover the ground with black polythene and leave it for several _weeks_, but even then some will regrow from their roots.
-- MaxwellBuchanan, Jul 11 2015


[MaxwellBuchanan], I tend to expect that when the spray is applied, the ground around the plant will be covered, too. And as indicated, how long the cover lasts depends upon the weather.
-- Vernon, Jul 11 2015


This is a simple enough experiment to do. Let us know how it goes.
-- MaxwellBuchanan, Jul 11 2015


There is a germ of a sci fi concept here: to want to kill something but to want the thing to look good, robust and healthy. Not obviously dying as it dies. A sci fi or a murder mystery.
-- bungston, Jul 11 2015


Won't every species eventually be tagged for death by a unique metabolic pathway from it's chromosomal variation?
-- wjt, Jul 12 2015


Eventually?
-- bungston, Jul 12 2015


Either technological design or nature's relentless subtle chew.
-- wjt, Jul 13 2015


It's a bit of an assumption to say that green paint will absorb everything except for green light*. You may find that it absorbs some frequencies, but is transparent to others - which will pass straight through to provide life-giving energy to the leaves of the weed you've just spent ages painting.

[*] Quick thought-experiment: Is cheap green paint likely to be opaque in the IR, UV, or X-Ray spectra?
-- hippo, Jul 13 2015


Make a small robot with a camera and web access to plant recognition websites. (We have at least two in Israel). Have a whitelist and blacklist of plants, and if unidentified send to the weeder company for decision. The robot runs on methane from dry weeds composted in its stomach and solar panels.

Don't forget to paint it green.
-- pashute, Jul 13 2015



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