Brief History of Potash in the U.S.
I recently learned that the first U.S. patent issued was to Samuel Hopkins in 1790 for his process that improved making potash. The patent was signed by President George Washington, Attorney General Edmund Randolph, and Secretary of State Thomas Jefferson. Since the terms "potash" and "potassium" are used a lot when talking about plant nutrients, I wanted to answer the question, "What is potash?"!
In those times, potash was a hot commodity, used for making soap and bleaching textiles, such as wool. The process for making potash was to soak and boil hardwood tree ashes in a pot. "Pot ash" became "potash"! The word potassium is derived from potash.
There was plenty of hardwood ash since a lot of land was cleared and burned to make room for homesteads and selling ash became a way for settlers to make some money. Hardwood trees such as maple, elm and hickory produced the most potash.
What is Potash?
Today, the primary use for potash is providing potassium, a macro-nutrient, in fertilizer; the "K" in "NPK"! The element potassium doesn't occur by itself in nature, but does exist in different potash "forms". It's no longer manufactured by boiling ash in a pot; it's mined. The word has also expanded and now encompasses any compound that contains water soluble potassium.
Examples of these different forms of potash include potassium carbonate (the original potash from boiling wood ash), potassium hydroxide (lye), potassium nitrate (used in rocket propellant and fireworks) and potassium chloride (used extensively in the medical industry).
Potassium on Nutrient Labels
Fertilizer and nutrient manufacturers use different forms of potash as the source of potassium for their products. Some may even use more than one form of potash. For example, a nutrient manufacturer might use both potassium nitrate and potassium sulfate to provide the potassium for their vegetative nutrient line. A different manufacturer might use potassium nitrate and potassium phosphate for their vegetative nutrients.
You will often see labels on fertilizer and plant nutrient bottles, giving amounts of "K2O", Potassium Oxide, instead of just "K" when listing the amount of potassium. Potassium Oxide is used as standard unit of measurement for comparing amounts of potash. Since potash comes in different forms (potassium carbonate, potassium sulfate, etc.), it's hard to know how much potassium one form has over another. Comparing K2O between different types of potash allows you to compare different amounts of potassium.
Benefits of Potassium in Plants
Potassium plays a role in several crucial functions of plants and provides many benefits. Potassium is often considered to be the nutrient that influences plants' quality.
Potassium regulates the opening and closing of stomata in plants' leaves. These pores regulate gas (oxygen and carbon dioxide) exchange and is therefore critical in the photosynthesis process.
Potassium improves and regulates water uptake and loss and improves water retention.
As the "quality" nutrient, potassium improves food crops' taste, color, texture and improves its nutrient value.
Potassium helps the plant combat stresses from temperature and light extremes and metal toxicity.
Potash and Potassium
Often, the words potash and potassium are used interchangeably in indoor gardening and can be confusing when reading nutrient labels.
As you've seen, potash played an important role in the United States' early economic development. Regardless of which form, potassium is the main constituent and since its one of the macro-nutrients, potash plays an important role in plants!