Potassium, also known as potash, is an essential element for plant growth and is required in the same quantities as nitrogen. It is commonly applied to gardens, lawns and orchards as part of a balanced fertilizer. Potassium, helps plants use water, and resist drought. It also promotes healthy green lawns. It affects the size and quality of flowers and fruit, and is essential for the synthesis of protein and carbohydrates. Potassium deficiency results in small, inferior flowers and fruit. The plants themselves will also be stunted. It shows up in older leaves particularly, as a yellowing around the edge of the leaves, followed by a brown scorching. Alternatively, the leaves may become bluish and eventually bronzed all over. An excess of potassium can result in plants not being able to take up magnesium and could cause an imbalance with other elements.
Plants take more potassium out of the soil than any other element except for nitrogen and calcium. This is because only one percent of the potassium that naturally occurs in soil is in a form that can be used by plants. When shopping for plant foods and fertilizers, make sure that the potassium you're buying will actually go into your plants.
Another good thing to know is that plants get their potassium by moving their roots through the soil. You should mix fertilizers and plant foods deep into pots and planters, where the roots are. You can also use fertilizer sticks to reach the root areas of plants and flowers that are already well-established in planters.