Growth slows down and the plant gives a poor yield of fruit and seeds. Generally, an excess of phosphate is not detrimental to most plants, as the root system closely regulates the uptake. Gardeners frequently use potassium or potash to improve the brightness of flowers as well helping cut flowers last longer. Potassium also helps toughen up plants, making them more resistant to pests and diseases. Potassium can also help, but not eliminate, problems caused by excess nitrogen.
Potassium also plays an important part in the formation of sugars and starches.
A deficiency of Potash shows first as yellowing of the edges of leaves. The entire leaf may become brown and scorched looking if the deficiency continues. Sometimes scorch shows up as leaf spotting and often starts at the base of the plant. In severe cases, an entire plant can collapse and die. An excess of potassium is also bad for plants since this can cause too much water to be absorbed, increasing water demand and, in the high desert and mountainous regions of the County, reducing frost resistance.