When the nutrients around the root zone are depleted, plants suffer. Without regular nutrients, growth slows, flowering is inhibited, and the plant becomes vulnerable to pests and disease.
There are three main food groups that plants need for vigorous growth, expressed as N-P-K. Each nutrient is responsible for different types of growth and aspects of plant health. All are essential in varying amounts.
N – Nitrogen promotes leaf and stem growth. It’s important for evergreens, foliage plants and ornamental grasses.
P – Phosphorous relates to flower and fruit production, which is crucial to fruit trees, roses and ornamental berry-producing shrubs.
K – Potassium helps a plant’s immune system fight disease, and also helps fruit to ripen more quickly.
Each fertilizer is labeled with three numbers that indicate the strength by percentage of each nutrient. For example, 23-6-8 means that the product contains 23% nitrogen, 6% phosphorous, and 8% potassium.
Organic and synthetic. Organic fertilizers are produced naturally and include compost or manure. Synthetic fertilizers are produced chemically, and include most granular fertilizers. Synthetic fertilizers contain exactly what’s on their label expressed as N-P-K. They are fast acting but here today and gone tomorrow, so you must apply them often. Organic fertilizers also bear N-P-K percentages on the label, but these are usually lower numbers. Organics are slower to take effect because they must interact with soil microorganisms, but are long lasting. Natural fertilizers contain many of the lesser nutrients too, which improve soil and overall plant health.
Certain plants need special combinations of nutrients. Roses are a good example. Citrus is another. Read plant labels for exact nutritional needs for your plants.