Roots Organics HPK - 32oz This liquid bloom booster features a combination of seabird guano distilled it into a distinctive, easy-to-use formula for the home and professional gardener. It is an unparalleled source of available natural phosphorus, phosphate rock, and langbeinite, a natural source of potassium that is carefully mined from ancient sea beds in the deserts of the American Southwest. Taken generations of gardening experience and HPK is minimally processed to preserve all the benefits and amazing synergistic qualities found in the exceptional ingredients.