Routine applications of fertilizer promote healthy growth in lawns, trees, shrubs, veggie gardens and flower beds. A stop at our garden center reveals many choices and brands of fertilizers. Why so many choices, what do they all do? Here are some fertilizer basics and guidelines to help make an informed choice.
What’s in Fertilizer?
Three main chemical elements are found in all mixed fertilizers:
N = Nitrogen promotes healthy leaf growth by stimulating the production of chlorophyll (the main chemical involved in photosynthesis).
P = Phosphorus helps with the development of roots, stems, blossoms, and fruits.
K = Potassium for overall health and vigor, helps plants digest and manufacture their foods.
These elements are listed in this sequence on the label of all fertilizers. Complete fertilizers will have some of each element, for example, 5-10-5. A balanced fertilizer will have about the same portion of each, for example, 15-15-15. Specialty fertilizers may have a greater portion of one of these elements, to support a specific kind of growth. Lawn fertilizers, for example, will be high in Nitrogen (N) for lush, leafy growth. Fertilizers for flowers or fruiting plants like veggies will have a higher middle number (P) like 10-15-10.
There are also a variety of minerals in fertilizers such as iron, calcium, copper, and magnesium that may be part of a given fertilizer’s composition. These will be listed on the label.
Liquid vs Granular Fertilizer:
Each has its own uses depending on the plants’ needs. Liquid fertilizers provide immediate nutrition to a plant. Liquids are perfect for plants that need a quick pick-up.
Granular Fertilizers provide nutrients that take longer to be absorbed into the plants’ tissues. These are great for spring applications to last well into the growing season.
Organic vs Conventional: The main difference between organics and conventional fertilizer is the source of the nutrients. Organics are derived from animal and plant waste. The N-P-K ratio of organics will be much lower than that of synthetic fertilizers and are slower acting. For this reason, it is less likely to ‘burn’ plants using organic fertilizer. Organics often benefit the soil as well as the plants. Conventional fertilizers are manufactured synthetically using chemical processes. Synthetic fertilizers are faster acting, less expensive and generally have higher N-P-K ratios.
When to fertilize:
There’s no point fertilizing plants unless they’re actively growing. Veggies, trees, shrubs and flowers will all reward you with lush, healthy growth for feeding them a balanced granular fertilizer in the spring. Lawns benefit from spring fertilizer as well as summer and late fall for continued green, leafy growth. Hanging baskets and flowering annuals like the regular addition of liquid fertilizer mid- July through September. Bulbs need fertilizer at planting time in the fall.
How to apply: Liquid fertilizers can be mixed in a large bucket or watering can and applied all over the plant, including the foliage and root zone.
Granular fertilizers can be placed in a spreader for larger areas like lawns and flower beds or can be measured out and sprinkled around the base of each individual plant. Brush any granular fertilizer from the leaves so they don’t burn.
More is not better in the case of fertilizer. Over-applying can lead to spindly growth or can burn the plants. Avoid applying fertilizer in the heat of the day and water thoroughly after applying granular fertilizer.
It is up to the user to read the product instructions and follow them precisely.