How often do you spray roundup?

Answer 1

Roundup should only be used once, since it is quite effective on just the first application.

AnswerGlyphosate herbicide (Roundup is one brand name) may be used (at least in the US) anytime new weed growth is observed in the field. It is important to use the correct rates to help prevent development of herbicide resistance in tough-to-kill weed species. Since some weed species are not susceptible to glyphosate, you need to know what species you are trying to kill.

Always read, understand, and follow all label instructions before using ANY pesticide!! It is unlawful to use any pesticide in a manner inconsistent with its labeling.