The lack of water and nutrients, and weeds and pests cause the primary stress for the plants. Planting site where soil contains heavy metals or organic wastes that could contaminate the herbs can not be used for production. Among the others, harmful residues of lead and cadmium are unfortunately sometimes detected in herbal products. Appropriate use of herbicides, insecticides, fungicides will limit pesticide residues in the herbs. Due to certain concerns about the cultivation methods a growing number of consumers are preferring organically produced herbs.
Weeds are a serious problem for the grower.
Weeds compete with the herbs for soil nutrients, water, and light. They also can serve as hosts for diseases and insects that attract herbs. The presence of weeds in the plant material decreases the external quality and market value of herbs. In areas where natural rainfall is insufficient, irrigation is necessary. However, herbs should not be overwatered since most are susceptible to root rots that thrive in wet soil.