What Is Osmocote Fertilizer?

Osmocote is a popular houseplant and garden fertilizer that works in tandem with the plant's natural growth cycle. Since Osmocote is relatively expensive when compared with regular organic fertilizer, gardeners usually reserve its use for only their most prized bedding flowers, vegetables, houseplants, or other container-grown plants. Though it contains no harsh chemicals, it is a synthetic product.

Osmocote has a very distinctive appearance. It looks like small, round peppercorns of a creamy beige color. Rather than being called granules, Osmocote particles are known as prills. The beige shell on the prill coats a core of nutrients.

Prills can either be scattered over the garden soil or else incorporated into the soil at planting time. As soil warms and rain or irrigation reaches the prills, the coating allows internal nutrients to trickle out into the adjacent soil — via osmosis — for plant roots to absorb.

What does it mean when claims are made that Osmocote works with a plant's natural growth cycle? The fact is, the prills disintegrate faster into the soil when the plant is growing faster.

Osmocote fertilizer prills are coated with a polymer that changes porosity based on temperature. As moist garden soil temperatures warm, the pores increase in size to release more nutrients. This relationship to temperature correlates to increased growth of plants, which means that the nutrient release is timed perfectly for plant use. As the soil cools, the prill pores tighten and fewer nutrients are released. Depending on the thickness of the polymer layer, the nutrients in a prill can last for three to 12 months.

There are a number of different Osmocote fertilizer products, each one recommended for specific uses. Each formulation has precise use instructions on the packaging and these should generally be followed. Many can be used either for houseplants or for flower or vegetable gardens.

The general recommendation for garden fertilizer is to sprinkle Osmocote fertilizer prills on the top of the soil at planting, then to mix the prills carefully into the top layer. It is also possible to simply leave the prills on a worked soil surface.

But generally, Osmocote fertilizers are somewhat pricey to be scattered rashly across large expanses of the garden. Well-balanced, quality, slow-release fertilizers work just fine for most plants and come at a lower cost. Many gardeners reserve Osmocote fertilizer for the fast-growing plants that are grown from spring to fall, or for houseplants. There is a houseplant-specific product termed "Potshots" that makes feeding your potted plants easy with a premeasured blend of essential nutrients in one nugget of fertilizer.

Note that Osmocote prills release nutrients slowly and gradually as long as the soil temperatures remain below 80 degrees Fahrenheit. However, in hot summer regions, the elevated soil temperatures can speed up Osmocote prill degradation, shortening the longevity of the fertilizer.