Trees are the most low-maintenance plant within a landscape. Because they require so little attention, they are often overlooked when it comes to feeding. Just as the shrubs, grasses and other elements of the yard or garden receive a regular feeding to promote growth and health, so too should trees. Fertilizer selection determines the frequency and quantity of tree nutrients to provide.
Naturally occurring, organic fertilizers are the preference of many gardeners. Examples of organic fertilizers are seaweed, fish emulsions and bone meal. While hard to determine the exact amount of nutrient these fertilizers provide per application, they provide a natural source of fertilization to the tree's roots. The absorption rate of organic fertilizers is longer than its inorganic cousin; they must first decompose in order to provide a source of food.
Artificially manufactured from a large variety of sources, inorganic tree fertilizers are the most common. Primarily containing valuable tree nutrients such as nitrogen (N), phosphorous (P) and potassium (K), the concentration of these elements are predetermined. A concentration of 10-5-5 indicated on the fertilizer's packaging reveals the exact proportion of each component it contains. In the example given, this fertilizer contains 10 percent by weight of nitrogen, 5
percent by weight of phosphorous and 5 percent by weight of potassium. Incidentally, a 10-5-5 fertilizer ratio is good for tree feeding.
Both organic and inorganic fertilizers are available in liquid form. An advantage of using a liquid fertilizer over other forms is its ability to penetrate the soil and reach the root bed. The disadvantage is how quickly it leaches into the surrounding soil and does not provide a sustaining food source.
Tree spike fertilizers are a popular option for supplying a year-round source of nutrients and minerals. Driven into the ground around the outer edges of the tree's root zone, spikes dissolve over time during feeding. The size of the tree determines the number of fertilizer spikes to use.
By far the most common form of fertilizer is the granular variety. Bags or packages of 5 to 100 pounds are available to satisfy any size of job. Granular fertilizers are spread over the ground directly above the entire root zone. They can be either watered into the soil, or they can naturally dissolve down to the roots with time. Similar to spikes, granular tree fertilizers continue feeding over time as they dissolve. This provides another lasting food source for trees.