Understanding fertilizing your container Citrus should begin with some words of caution. Fertilizing should never be administered as a medicine to cure a poorly performing plant. This means that a properly fertilize plant should never need fertilizing to cure poor performance.
For example, plants grown in the nursery receive consistent care, which includes proper feeding. When one receives a new plant, typical symptoms that might arise from the adjustment to a new location - such as yellowing leaf, leaf wilt and leaf drop - rarely have anything to do with the plant’s nutrition. Most often these symptoms are the result of changes in the plants environment such as lower light, exposure to an excessively dry environment or over watering. All care should be given to providing the best location for your citrus plant and developing watering habits with attention to keeping your Citrus plant on the dry side.
Only after you have found a spot with consistent light and understand how to water without over watering does the need for a consistent fertilizing program come into play.
If you receive your plant in the fall, odds are that it has been fed at the nursery to support hardiness going into the winter. There should be no need for another application until later in the winter.
A properly fertilized young container Citrus is one that has applications of organic fertilizer applied quarterly beginning in late winter. As the tree grows into larger containers the feeding becomes more frequent. Citrus likes an acidic soil, so it is preferable to use an acid based fertilizers.
Acid fertilizers are fertilizers traditionally recommended for Azaleas, Camelias and Rhododendrons.
An acid soil mix consisting of Bark, Peat Moss, and Coir are always recommended for Citrus container planting.
Acid Fertilizer helps to maintain the pH of your soil at a level suitable for citrus. This is of concern if you know your waters pH is 7 or above. Your water purveyor will provide your water’s pH, and a simple soil test kit can tell you your soil’s pH. It is recommended that organic fertilizers be applied by following the recommendations on the bag for your fertilizer.
To adjust the pH of soil, an application of Soil Sulfur or regular additions of Cottonseed Meal can help to maintain a healthy pH between 5.8 and 6.0.
High Nitrogen fertilizers quite often affect the health of the soil and the growth of the tree by disturbing the soil biology. They are not recommended for container growing of citrus.
All container Citrus plants should be mulched. Mulching has the same effect in a container that it does in the ground. It works to keep roots cool in hot weather, cuts down on evaporation, increases the time between watering, keeps weeds down and in time will provide a nutrient source as it breaks down into organic matter.
Applying organic fertilizers to mulched container Citrus can pose a challenge as the fertilizer will rest and cake on top of your mulch. Make sure to distribute your fertilizer evenly around the surface in the pot and water in thoroughly until the fertilizer works down into your mulch.
Maintaining the mulch layer inside your container will also help to maintain the microbiology inside. Try not to disturb the mulch - but do add fresh mulch to the surface yearly or as needed. Try to maintain a 2-inch layer inside of the container.
Raising Citrus in a container is like raising fish in a fish tank. The chemistry in the container-grown Citrus plant depends on you providing the food that supports the biology in the soil that feeds the plants root system and in turn keeps your tree healthy.