The citrus tree is a perennial-growing tree that produces more fruit worldwide than apples, peaches and pears combined. Options for the home gardener are abundant when it comes to citrus. Almost all sizes are available, from the conventional backyard tree to semi-dwarf and dwarf. Fruit size is not affected by tree size. Trees can be planted in the yard, in pots and espalied along a wall or fence.
The success of fruit production depends on adequate nutrition. Lack of nutrients results in deficiencies that reduce fruit yield. Size, color, sweetness and peel texture are closely linked to proper care of the tree. Nitrogen is an important nutrient when it comes to citrus. Other nutrients, unless lacking in the soil, do not need frequent replenishment.
Citrus trees do not bear fruit in the first two to three years. Trees at this stage have different requirements than a more mature tree. Non-bearing trees should be given 1 tbsp. of nitrogen fertilizer in the form of ammonium nitrate or urea every three or four weeks. Application should occur over the root area, but 1 to 2 feet from the drip line, and be watered in completely. This is approximately 1/10 of a lb. of nitrogen fertilizer per year. A 3-year-old tree can be given 1/4 lb. per year, and a 4-year-old tree can move up to 1/2 lb. per year.
Fully Bearing Trees
Fully bearing trees that are average size should be given 1 lb. per year of nitrogen. The fertilizer package of ammonium nitrate may read 33-0-0. The number 33 indicates 33 percent nitrogen. This means that in order to supply 1 lb. per year, 3 lbs. of this particular fertilizer will need to be applied. Trees that are dwarf and semi-dwarf will require a smaller amount of fertilizer which will depend on the size of the tree canopy.
Proper levels of nitrogen are required during flowering and fruit setting. A broadcast fertilizer in the late winter or early spring is recommended. High levels of nitrogen during the summer do not benefit oranges and grapefruit, while lemons respond well to an additional nitrogen boost during this season.
Trees grown in containers require more of a nutrient supply. A complete, slow-release fertilizer is preferable. Often, nitrogen and micronutrients, especially boron, are washed from the container and deficiencies occur. A foliar spray can temporarily address this problem. Application is most effective when leaves are approaching full size. Generally, this is during the spring