NPK
Growing and care
NPK rating is a government mandated rating system describing the amount of nitrogen, phosphorus, and potassium. NPK ratings consist of three numbers separated by dashes (e.g., 10-10-10 or 16-4-8) describes the chemical content of fertilizers. The first number represents the percentage of nitrogen in the product; the second number, P2O5 consists of 56.4% oxygen and 43.6% elemental phosphorus; the third, K2O consists of 17% oxygen and 83% elemental potassium. The generalized form is N-P-K. A 50-pound bag of fertilizer labeled 16-4-8 contains 8 pounds of nitrogen (16% of the 50 pounds), 2 pounds of P2O5 (4% of 50 pounds), and 4 pounds of K2O (8% of 50 pounds). Australian convention adds a fourth number for Sulphur. Although unimportant in a practical sense, fertilizers do not contain P2O5 or K2O per se. These concise formulas are shorthand for the nature of the phosphorus (phosphate) or potassium (K+) sources.
Plumeria Database context: NPK affects how plumeria roots, leaves, stems, and blooms perform in containers or in the ground. Care terms are especially important because watering, drainage, nutrition, and soil conditions can change the way a plant looks.
What to look for: Consider the growing mix, drainage, watering cycle, fertilizer program, container size, root health, and local climate before deciding whether a symptom is a cultivar trait or a growing-condition response.
Identification note: This term is one clue. A plumeria should be compared using all available traits, photos, source history, and growing context rather than a single characteristic.