Citrus Fertilizer & Organic Amendments

What nutrients are important for a healthy citrus tree?

Fertilizers 101

Nitrogen, phosphorous and potassium are called macronutrients. All non-macronutrients are called micronutrients.

Familiarize yourself with each fertilizer’s ingredient list. You will see three numbers with hyphens in between them like 4-15-2. These represent the nitrogen-phosphorous-potassium ratio or NPK ratio of the material, in that order.  Almost every product will have this ratio listed out on the front or side of the packaging. Locate the nutrition table on the packaging to see the full ingredient list and percentages. The remainder not listed out should be assumed as filler material.

Citrus trees are heavy nitrogen feeders, especially during the summer growing season. Generally, you’ll want some nitrogen in your feeding application even if the feeding’s purpose is to add some other nutrient.

Do the math to save money

Just because you can get more pounds of fertilizer per dollar does not mean that it is the financially prudent option. Some basic algebra will reveal the best bang for the buck.

For instance, a fertilizer with a NPK ratio of 7-3-3 is half the amount of nitrogen, phosphorous, and potassium as a 14-6-6 fertilizer per pound. So if the 14-6-6 product is in a 5 pound bag and the 7-3-3 product is in a less than 10 pound bag, you should purchase the 14-6-6 fertilizer despite the smaller bag size.

Create a customized feeding schedule

Do you need more potassium after fruit starts forming or before? What about more phosphorous in the spring as opposed to the fall?

These are great questions. The answer to both questions is yes. Discovering answers to similar lines of questioning should influence your fertilizer purchasing decisions.  I have multiple citrus fertilizer products each with different NPK ratios for different times of the year as the nutritional demands of my trees change.

In the spring, nitrogen and phosphorus are very important. Nitrogen is necessary for stemming growth.  Phosphorous aids in disease prevention and also supports strong roots. Potassium becomes absolutely essential during fruit production. Once fruit sets, fruit starved from potassium will likely not grow as large or reach the same quality.


Feeding Citrus in the Spring and Summer

Citrus fertilizer should be applied monthly April-September during the growing season. The Spring and Summer are when most trees bloom, form fruit, and grow branches. During this period it’s crucial to be steadfast in supplying nutrients as your citrus shows you what they need. Keep in mind that heavy rainfall means the nutrients you add will leech out sooner. When this occurs, fast-forward your next feeding time.

Feeding Citrus in the Fall and Winter

With diminishing sunlight and decreasing temperature, your citrus tries will become semi-dormant. The number of resources expended will diminish and so should the frequency of your fertilizer application. Reduce your feeding to every other month starting in October. Remember to always water after adding fertilizer.

Foliar Spray

Nutrients being taken up through the roots have limitations caused by disease, temperature, and PH level. To overcome some problems, fertilizer can be sprayed directly onto the foliage and be processed much sooner than it would take the roots. Even the trunk and branches can absorb the nutrients. You can also spray into the soil if wanted.

Aim for spraying on the epidermis and the stomata of the leaves. Make sure to spray underneath to for optimal surface area.

Foliar spray can come premixed or in powder form. I use 3 foliar sprays. One purchased as premixed and two in powder form. The premixed foliar spray is called Citrus Nutritional Spray by Southern Ag. It contains 5 “trace” nutrients that granular fertilizer doesn’t have enough of or your tree’s condition does not allow to be taken up by the roots. These five nutrients are iron, magnesium, zinc, manganese, and sulfur.

My other two products for foliar applications are from a brand called Peters. These are macronutrients sprays. One has a balanced NPK ration of 20-20-20. The other is oriented for growth and blooming during the spring with a 10-20-10, where 20 represents the phosphorous part of the ratio.

These three products cover all the cases in which I would need and/or want to use a foliar spray. Sometimes it’ll be used to revive a plant and in other cases it will just be your normal schedule to spray the 10-20-10 during the spring and the 20-20-20 all through the summer into fall.

I highly recommend stocking at least one foliar spray in additional to your granular fertilizer.

What Products do I Use?

Granular Fertilizers

Foliar Fertilizers

Osmocote Smart Release Plant Food Plus

Espoma Citrus-tone fertlizer

Jobes Organics Fruit and Citrus Fertlizer

Espoma Blood Meal Plant Food

Espoma Organic Traditions Bone Meal

Espoma Soild Acidifier

Espoma Triple Phosphate

Down To Earth Alfalfa Meal

Monterey Dr Iron