Growers are well aware of the major elements (macronutrients) required for plant growth (NPK, Calcium, Magnesium and Sulphur) but tend to overlook the importance and balance of micronutrients. Plants need micronutrients from the growth of the first true leaf. Most commercial soilless growing composts consist of a variety of inorganic and organic components and the levels and availability of micronutrients are variable and inconsistent. Micronutrients can be applied as water soluble fertilizers. However, too high a level can also be toxic and some species are particularly susceptible to excessive boron, such as: Begonia, Gerbera, Impatiens, Tagetes, Lantana, Viola and Zinnia. Some species including Pelargonium and Tagetes will accumulate iron and manganese to toxic levels if the pH of the substrate drops below 6. In general plants grown in alkaline substrates often suffer from from micronutrient deficiencies. Zinc deficiency is more common in Pelargonium, Vinca and Zinnia. Copper deficincy is well-known in non-stop fibrous Begonia, Tagetes and Petunia. Iron deficiency can easaily be encountered in Pelargonium, Salvia and Verbena. Muhammad Younus, Greenhouse Canada www.greenhousecanada.com E-mail: greenhouse@annexweb.com