Nature&#39;s Avenger Organic Weed Killer Concentrate, 1 gallon Avenger organic weed killer concentrate is a non-selective, post-emergence herbicide that quickly and effectively kills weeds, grasses and broadleaves The active ingredient D-limonene (citrus oil) naturally strips away the waxy plant cuticle, causing it to dehydrate and die Approved for use in organic gardening by the U.S. Department of agriculture's (USDA) national organic program (NOP) rule Small annual weeds: for the control of annual weeds less than 6 inches tall, use a 1:6 ratio