Citrus trees are heavy feeders, which means they usually require more frequent applications of fertilizer. As a general rule, citrus trees need more fertilizer in the growing season, typically spring and summer, and less in dormancy. Fertilizing every two months in spring and summer and every three or four months in fall and winter will assure the trees get the nutrients and micronutrients they need to thrive. Depending on the soil and the condition and age of the tree, different micronutrients may be required.
Citrus Fertilizer Contents
Like most all trees, citrus trees require nitrogen, phosphorous and potassium. In addition to these nutrients, citrus tees also need micronutrients such as copper, zinc, boron and magnesium. Other nutrients may be required depending on the soil. Iron deficiency is common among citrus trees. An iron supplement can be easily added to the soil. Citrus also requires acidic soil, so look for a highly acidic fertilizer.
There are two main methods for fertilizing citrus trees. One employs liquid fertilizer, which is sprayed on the leaves and around the base of the tree. The other involves granular fertilizer, which is applied at the drip line of the tree's canopy, and then watered into the soil. Fertilizer spikes may also be used, but can be dangerous to young trees. They are best reserved for use on mature trees.
When to Fertilize
When the growing season begins (around March in the southern states and around May in states further north) more aggressive fertilizing is needed. As often as once a month is not unusual, but usually every two months will suffice. Trees with pale green leaves are in need of frequent applications. Trees that are verdant, with lush green leaves, do not require as many nutrients. In late fall and winter, when trees are dormant, decrease fertilizing to once every three months.
A young tree that is 1 or 2 years old needs a quarter pound of nitrogen a year. A tree that is 2 or 3 years old needs half a pound a year. A small adult tree, 3 to 5 years old, requires a pound of nitrogen, whereas a fully grown tree requires 1.5 pounds of nitrogen. These figures represent nitrogen only. When applying fertilizer, read the package to determine what percentage of the total is nitrogen. This way, you can determine how often to fertilize, and how much to apply.
Trust Your Eyes
When the leaves of the citrus trees turn yellow or are misshapen and poorly formed, it's a good indication of a lack of nutrients. Fruit that is poor quality, dwarfed, misshapen or discolored also indicates a lack of nutrients. Choose these times to apply a good-quality, high-nitrogen fertilizer.