Calcium is part of a compound in the cell wall. Magnesium is present in chlorophyll, the green in the plants. Sulfur affects cell division and formation. Manganese, iron, copper, zinc and cobalt influence plant growth by serving as activators or catalysts. Boron is associated with calcium use and molybdenum is essential in nitrogen use.
Many gardeners fail to understand how much fertilizer is in each bag.
If the bag has trace elements or micronutrients, they will be listed and the percentages will be much smaller. The other 30 pounds in the 50-pound bag is made up of filler or carrier for the nutrients. Crape myrtles need a high nitrogen lawn-type fertilizer now to stimulate vegetative growth, followed by one higher in phosphorus for bloom. Roses need fertilizer about every six weeks from spring until late summer. Fertilize azaleas and camellias after bloom and again in six weeks.