Flaming can set back larger weeds, but zapping weeds as tiny seedlings or before they have three or four leaves is best. Killing small weeds, you will have more predictable success at field speeds and fuel use competitive with mechanical or herbicide passes. For guidelines, flaming experts say Don t burn weeds. If weeds are toasted, you re wasting fuel. Energy-efficient flaming will have little immediate visible effect but will cause weeds to droop and wilt within a few hours.
Timing is everything.
This gives the crop the least weed competition during its most vulnerable stage. Early postemergence flaming works, too, for crops that send up early leaves before their growing point emerges. Even if the young leaves are singed, these crops will bounce back as long as the growing point survives. Once the growing point emerges, allow substantial growth before flaming stalks. Run when it s hot and dry.