The effect of Odocoileus virginianus (White-tailed Deer) on Lupinus perennis (Sundial Lupine) was quantified for a site in Worcester County, MD. The reproductive output of Lupine protected by deer exclosures was compared with Lupine that received no protection from deer. Lupine in the exclosures had a higher likelihood of producing seed pods and produced a greater number of seed pods per inflorescence. The implications of these results on Callophrys irus (Frosted Elfins) are discussed.