It stimulates bud-set and blooming. Potassium, the last of the big three, is important for increasing vigor and producing strong stiff stalks. It helps impart winter hardiness in plants. The secondary and micronutrients are also important. 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.