Citral is a monoterpene commonly found as volatile component in many different aromatic plants. Although many studies have identified the presence of citral in phytotoxic essential oils, this work determines for the first time the potential herbicidal effect of citral on weeds. The use of citral against weeds and crops resulted in the potential for the management of barnyardgrass, redroot pigweed, and ribwort. Clear morphological differences were observed between adult thale cress plants exposed to citral in two different application methods: spraying and watering. Citral-sprayed and citral-watered thale cress plants showed completely different effects after treatment, suggesting that foliar or root absorption can determine the effectiveness of this compound. This work demonstrates that citral is effective not only on seedling metabolism but also on adult plants by inhibiting growth and development altering the plant oxidative status.