A naturally occurring mineral in small quantities in garden soil, potassium is denoted by the third number on the label of fertilizer containers (such as the "15" in 10-5-15) and is further identified by the letter "K." It is contained in virtually every fertilizer mixture, with few exceptions, because it is so vital to the healthy growth of plants and the formation of flowers and fruits. The addition of potassium nitrate to a fertilizer mix has the identical effect on plant growth as other forms of potassium. To the plants, potassium is potassium, whatever humans call it or classify it as. Because of its high cost, potassium nitrate is not widely used in fertilizer mixes, according to the University of Minnesota Extension. Less expensive forms of available potassium are used instead. Adequate levels of potassium will help your garden flowers and vegetables grow bigger, healthier flowers and large succulent fruits and vegetables with a minimum of problems from pests and diseases.
Promotes Fruit Growth
Begin feeding your plants fertilizer high in potassium when they begin to set flower buds. It will help more buds set fruit and encourages the plant to produce even more flowers and fruits.
Control Root Growth
Potassium encourages plants to develop robust, healthy root systems. Ensure that the fertilizer mixture you feed to seedlings contains at least a little potassium, to encourage them to grow roots. Once they begin to produce flowers and you switch to a fertilizer containing a higher amount of potassium, their roots will more fully develop.
Helps Plants Resist Drought
Potassium's ability to foster strong root development also aids plants in their ability to withstand drought. A strong root system can more easily dive deep into the subsoil to find moisture than a poorly formed one. Feeding your plants a fertilizer with an adequate amount of potassium will ensure that they resist summer drought and still flower and produce fruit.
Increases Plants' Resistance to Disease
Because potassium increases the overall health and vigor of plants, it also helps them to better resist diseases and withstand the ravages of garden pests. Healthy plants will shrug off the loss of a few leaves to pests or disease more easily than those that are already struggling. Potassium will help them do this and still produce a crop.