A variety of special lawn fertilizers may be found.
Winterizer fertilizers are typically high in nitrogen and potassium, and although advertised for fall application can be applied in spring as well. The nitrogen produces a flush of growth that helps build more energy through photosynthesis for winter storage. Potassium is used all year by grasses and is involved in heat and cold tolerance, disease resistance, and other stress tolerances.
Weed-n-feed are fertilizer products that contain either a broadleaf herbicide for weeds such as dandelions (recommended for fall application); others contain a preemergence herbicide to control crabgrass (recommended for spring application). Weed-n-feeds are products of convenience that compromise the ideal timing of either the fertilizer or the herbicide. This is most true with the spring weed and feed that controls crabgrass. Typically, to prevent crabgrass from germinating we need to put the product down in early April for central Illinois. However, this is too early for a spring fertilizer application. More information on the Dilemma of Weed and Feeds.
Lawn Starter Fertilizers
Lawn starter fertilizers are typically high in phosphorus and are intended for newly seeded lawns and freshly laid sod. Often Illinois soils have adequate amounts of phosphorous, but a soil test will reveal your nutrient levels. Test your soil.
Organic fertilizers are typically carbon-based forms of nitrogen. By their very nature, organic fertilizers are considered non-burning and are released to the turf plant over time to varying degrees based on soil temperature and moisture levels. Because these products often need to be broken down by soil microorganisms, if the soil is say too cold, the microorganisms will not break the material down as quickly. Unlike many synthetic fertilizers, often organic products contain proteins and other micronutrients that help feed soil microorganisms and promote soil health.
There are a variety of organic sources of nitrogen, phosphorus, and potassium available to the homeowner. Most organic fertilizers are derived from plant or animal sources. Plant sources would include alfalfa, cottonseed meal, and seaweed. Examples of animal sources would include bone meal, blood meal, and manures from chickens, cows, and horses. Yet another source comes directly from Mother Nature in the form of rock phosphate for a source of phosphorus and green sand for a source of potassium. Find and use products that are locally available whenever possible to keep the input costs down. It is important to note, that turfgrass does not care whether the nitrogen is from an organic source or synthetic source.