Vendors whose sites specifically state the horticultural method used in growing the plants from which their oils are distilled. Recent tests have indicated that pesticide residues do come through the process of steam distillation, so, depending upon your proposed use of the oils, certified organic status might be important to you. Wildcrafted essential oils - oils distilled from wild grown plants and trees - are also included in this category, as they meet the criteria of 'organic', but have not been certified as such.