Late summer to early fall may not be the showiest time for dandelions, but it’s the best time to eliminate them from your lawn. I usually avoid using toxic lawn chemicals, so I was curious to try the new Ortho Elementals Lawn Weed Killer sample that I received at the recent Garden Writers Association Symposium in Indianapolis. This broadleaf weed killer is made with naturally occurring iron. The active ingredient is iron HEDTA–or hydroxyethylenediaminetriacetic acid, for those of you studying organic chemistry!
The product works by creating iron toxicity at the cellular level. Because the mechanism of iron uptake is different in broadleaf plants such as dandelion from that in monocots such as lawn grass, the weeds die while the grass is unaffected. This naturally occurring chemical is reported to be safe for humans and other animals. Sprayed areas are safe to reenter as soon as the product dries. And further background research shows that iron HEDTA is not persistent, so it is quite friendly to the environment. Additionally, rather than spraying the entire yard, you’re supposed to spray only the dandelions (or other broadleaf weeds you want to eliminate), so much less chemical is used than with conventional weed killers.
The initial results are impressive. I spot sprayed dandelions in my yard this last weekend. In just 72 hours, they looked like the dandelion in the “after” photo below. The true test will be how much regrowth happens. The label indicates that for best results, two applications three to four weeks apart may be necessary. So I expect that the dandelions will regrow from the roots and need another shot of weed killer to wipe them out entirely.