Saltpeter, also called potassium nitrate, KNO3, and nitrate of potash, is a versatile substance used for gardening, stump removal, medicine, cooking, preserving meats, and making explosives. The purchase of saltpeter in large quantities is regulated by the U.S. federal government, due its explosive capabilities.
Potassium nitrate is often added to garden soils to increase nitrogen levels. Nitrogen helps feed plants and results in more lush and larger foliage. Potassium is a necessary element that will help prevent brown, curling leaves.
Saltpeter is generally purchased in powder form and can be mixed with water and sprayed on fruit trees. This product is valued for its quick release of nitrogen, which can act as a quick fix for mature fruiting trees and vines that are heavy with a ripening harvest. Used around garden plants such as tomatoes, saltpeter will help the fruit stay on the plant longer, avoiding ruined crops from early fruit drop.
Saltpeter is effective in speeding up the germination process of hard-shell seeds. Mix 1 tsp. of saltpeter in 1 quart of water, and soak seeds up to four hours in the solution. This helps soften the seed shell.