The quantity and quality of velvetleaf (Abutilon theophrasti Medic.) and giant foxtail (Setaria faberi Herr.) epicuticular wax (ECW) deposited under different environmental conditions was determined. The relationship of ECW to bentazon, fluazifop-P and acifluorfen uptake with and without the additives 28% N urea ammonium nitrate or crop oil concentrate (COC) was determined. Velvetleaf and giant foxtail formed more ECW when grown under drought stress (DS) or low temperature (LT) than when grown with soil moisture at field capacity (SMFC) or high temperature (HT). The primary alcohols decreased and hydrocarbons increased in the ECW for plants grown under DS compared to plants grown under SMFC. In giant foxtail, an increase in radiation energy decreased ECW fatty acids and aldehydes; in velvetleaf the secondary alcohols increased but esters decreased. HT caused a decrease in esters and an increase in hydrocarbons of velvetleaf ECW. The scanning electron micrographs showed changes in giant foxtails but not in velvetleaf ECW due to the environment. Bentazon and acifluorfen uptake without additives was not affected by ECW quantity or quality. The 28% N or COC improved herbicide uptake compared to no additive. Bentazon uptake was greater with COC than with 28% N when plants were grown under HT. However, uptake was higher with 28% N than COC when the plants were grown under LT. The ECW deposition restricted herbicide uptake with COC, therefore the COC appears to improve herbicide uptake by interacting physically with the ECW, probably by dissolving the ECW. Higher ECW favored herbicide penetration with 28% N, thus the ECW was apparently not a physical barrier to herbicide uptake. The 28% N could improve herbicide uptake by co-penetration or by chemical interactions with the ECW. Fluazifop-P uptake by giant foxtail was greater in plants grown in LT or SMFC compared to plants grown under HT or DS regardless of the additive. The higher uptake by LT grown plants can be due to changes in leaf anatomical or physiological characteristics. Plants grown under DS demonstrate less uptake due to the increase in hydrophobic properties and quantity of the ECW. The COC also appears to act by physically overcoming the ECW, while the 28% N seems to act by chemical interactions.