When you walk down the fertilizer aisle at the nursery or home improvement center, the second thing you’ll notice about the aisle (after the distinctive smell) is the array of formulations. You’ll see bags and bottles, powders and granules, sprays and concentrates. Furthermore, you’ll discover an increasing number of organic and “earth-friendly” fertilizers. Which one is best for your flowers? Make sense of these choices, and pick the best flower fertilizer for your plant’s healthy growth.
For most flower gardeners, a complete fertilizer is necessary to supply plants with the three major elements they require to thrive:
- Nitrogen (N): Promotes healthy foliage
- Phosphorus (P): Stimulates root systems
- Potassium (K): Aids in flower (and fruit) formation
The fertilizer label will list the nutrients in the order of NPK, with numbers representing the percentage of nutrient compared to filler ingredients. A 10-10-10 fertilizer contains 10% of each nutrient.
Fertilizer manufacturers create artificial fertilizers by combining inorganic chemicals to form compounds like ammonium nitrate or magnesium sulfate. An advantage of chemical fertilizers is that the plants take up the nutrients quickly, unless the formula is designed to be a time-release fertilizer. Disadvantages include the risk of over application, which causes burning, and the absence of any soil-improving qualities.
Chemical fertilizers come in a range of formulations, including pellets, liquid concentrates, and powders. These formulas make it convenient for the gardener to apply fertilizers to containers, houseplants, or the landscape.
Foliar fertilizers are liquid nutrients that plants absorb through their leaves. Not all flowers feed efficiently this way, because the waxes and hairs on leaves act as a barrier to nutrient uptake. Potassium is the most easily absorbed nutrient in foliar feeding applications, so use foliar fertilizers in the flower garden to address potassium deficiencies.
Organic fertilizers come from living things, like animal manure, fish emulsion, or leaf mold, and non-living things, like rock phosphate or greensand. Fertilizers from organic matter not only supply essential nutrients to flowers, they also improve soil tilth. Gardeners who don’t eat what they grow still appreciate organic fertilizers because they:
- Don’t burn plants
- Strengthen plants’ immune systems
- Are non-toxic to beneficial insects and wildlife
- Remain active in the soil for long periods
Disadvantages of organic fertilizers include their expense, palatability to some pets, and limited formulations. Organic fertilizers are not an overnight fix, so won’t correct severe nutrient deficiencies quickly.
If a soil test reveals a deficiency of one major nutrient, you can purchase a simple fertilizer, which contains only nitrogen, phosphorus, or potassium. Simple fertilizers can be chemical or organic in makeup.
Technically, all organic fertilizers are slow-release, as it takes time for organic matter to decompose in the presence of soil microorganisms. The slowest acting organic fertilizers include insoluble mineral fertilizers, like rock potash and other rock powders.
Gardeners who want to fertilize once and forget it can shop for slow-release fertilizers that use coatings or capsule-like shells to control the release of the fertilizer over a period of weeks or months.