Healthy lemon trees add the beauty of their thick foliage and dark green leaves to your yard, besides producing fruit. Lemonade made with your own home grown-lemons is a delicious summer treat. Gardeners are often surprised just how prolific a lemon tree can be in terms of fruit production. Besides protection from frost, the other major concern in growing lemon trees is proper fertilization.
The Need for Fertilizer
Fertilizing lemon trees helps support rapid growth of foliage in the spring, which in turn leads to bountiful fruit production. Fertilizing also combats nutrient deficiencies that can occur at various other times of the year. Lemon trees should have large, dark green leaves all over the tree. Pale leaves are an indication the plant requires fertilizer.
Type of Fertilizer
Fertilizers are labeled by their N-P-K ratio, the relative proportions by weight of nitrogen (N), phosphorous (P) and potassium (K). Nitrogen is the most critical nutrient added through fertilizing. Lemon trees are heavy consumers of nitrogen. You can supply this ammonium sulfate or ammonium phosphate. You can also buy specially formulated citrus tree fertilizers, which contain additional elements, such as iron.
When to Fertilize
Apply fertilizer to a lemon tree in the spring, before new growth appears. You can also do a second application when the tree has finished flowering and the plant is in its fruit production phase. A third feeding can be done at the end of summer to replenish nutrients that have been carried away from the tree roots either during heavy rains or from the irrigation necessary during the hottest months, particularly in the warmest climates.
How to Fertilize
A common application is 2 lbs. of ammonium sulfate per 100 square feet of area beneath the perimeter of the tree canopy, or dripline as it is sometimes called. Consult the directions on the fertilizer package. The suggested application varies by the relative amounts of N-P-K. Make a banked area of soil around the edge of the dripline. Fill the area with water to soften the soil. Spread the fertilizer as evenly as you can over the entire area. Then, resume watering. This second stage of irrigation helps drive the fertilizer down through the moistened soil so it comes in contact with the lemon tree's roots.
Lemon trees may also suffer iron deficiency, shown by yellow leaves streaked with green veins. This may result from over-watering, so the first step is to reduce the frequency of irrigation. The treatment for this condition is an application of fertilizer directly on the leaves when they are in early stages of growth. This method is called foliar feeding. Iron sulfate or chelate delivers the necessary iron. You may have to apply it several times to take effect.
What Not to Do
Never apply fertilizer just to the base of the tree. You want the nutrients to reach as far out the root system as possible. Watering the entire area within the dripline before fertilizing is important. Putting the fertilizer on dry soil can cause the tree roots to suffer burning. You don't need to worry about fertilizing the lemon tree the first spring after planting, but some gardeners work nutrients into the soil before planting the tree.