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Citrus Fertilizer: What, When, And How To Use It

Are you growing potted citrus trees or are you growing citrus fruits in your at-home garden? Are you considering starting your own citrus orchard? Well, then one of the most important tools you’ll need to have at your disposal is citrus fertilizer!

Citrus trees are persistent on their own, but they need love and care like any other fruit trees. That’s why it’s important to ensure each citrus tree has not only excellent base soil but a good fertilizer too. And there are plenty to choose from. 

So, today, we’re tackling citrus fertilizer. We’ll talk about the basic nutrition for citrus trees. We’ll also discuss the types of fertilizer on the market today. We’ll finish it up with some information on how to apply the citrus fertilizer you choose. That way you can grow delicious fruits that grow from a strong, healthy, abundant citrus tree.  

What Nutrients do Citrus Trees Need?

Healthy orange tree with citrus fertilizer applied
Citrus fertilizer keeps your trees at their healthiest. Source: HarlanH

Like all plants, citrus trees require the three basic building blocks of nutrients: nitrogen, phosphorous, and potassium. Did you know there are also three other macronutrients? These are calcium (Ca), magnesium (Mg), and sulfur (S). Without all 6 nutrients, plants have a hard time completing their life cycle. Most residential soil usually contains the latter three but often fluctuates in N, P, and K depending on what else has been grown in it and other factors.

Fruit trees also benefit greatly from the addition of micronutrients. These are found in trace amounts in healthy soil. They also come in many of the high-quality organic citrus tree fertilizer brands out there. A balance between the macro-nutrients (N, P, K, Ca, S, and Mg) and micronutrients ensures a healthy tree and luscious citrus fruits too. 

The micronutrients in question are manganese, zinc, iron, copper, boron, molybdenum, chlorine, and nickel. Deficiencies in any of these can cause different issues that may be hard to diagnose unless you know exactly what to look for. That’s why organic citrus fertilizer coupled with good base soil conditions are great ways to cover your nutrient bases. 

A citrus tree consumes a lot of nitrogen to produce new growth leaves that assist in nutrient absorption for flower and fruit production. Citrus trees also consume high amounts of calcium and potassium. These boost the flowering and fruiting of the tree and also feedback supporting other nutrient functions. More specifically, Ca is needed to develop strong root systems, and reinforce cell walls. Potassium feeds directly into fruit production and the development of viable seeds within that fruit. 

Citrus Fertilizer Formulas for Different Trees?

While you might see fertilizers specific to a type of citrus tree, the same fertilizer can likely be applied to another citrus tree with equal success. Most fertilizers on the market are more generalized and fertilize each citrus fruit tree equally. Adjustments in nutrient content don’t often occur in amounts that would matter much to lemon trees and lime trees. To lemon and lime, as long as they have the food they need to thrive, it’s all good!

So if you find a fertilizer that is generalized for citrus, know it most likely will work on your Meyer lemon tree just as well as it would on your navel orange tree. However, some formulations will work best with certain citrus, and provide basic nutrition for others. 

Types of Citrus Fertilizer

Pomelo on a tree
Large fruit such as this pomelo needs a lot of phosphorous to develop. Source: John and Anni

There are so many different types of fertilizer, with plenty made specifically for citrus trees. Let’s run down a list of the types of citrus plant fertilizer on the market today. While there are formulas that are designed for high performance, the best citrus fertilizer will be one suited to your needs and your schedule. 

Citrus Fertilizer Spikes

Spikes are best for potted citrus trees, rather than those in the ground. Different companies sell these. Fertilizer spikes utilize the nutrients potassium and phosphorus to feed citrus trees for producing fruit and flowers. Some go the extra step and include Mycorrhizal fungi and single-celled Archaea that work together to increase the productivity of the tree’s root mass. They’re used twice per year in the soil around trees. You can find spikes in most home improvement stores. 

Citrus Fertilizer Sprays

Sprays for your citrus fruit tree are meant to be applied to soil or the foliage of the tree. They include the basic macronutrients your citrus tree needs and then a few other nutrients, including zinc, iron, sulfur, manganese, and magnesium. Not only do these citrus fertilizers help you produce lush foliage, but they also provide increased plant performance in their ability to boost tree tolerance to cold, and heat, and even provide drought tolerance. These are applied during the dormant season. 

Citrus Fertilizer Powders

The Organic Materials Review Institute has put its stamp of approval on certain brands of powdered organic fertilizer. The fertilizers with OMRI endorsement have no synthetic chemicals and are generally formulated to be heavy on the potassium and phosphorus side of macronutrient content. Often these powders are specially created for large-scale citrus growers or those who produce a lot of citrus in the growing season. They’re used every couple of months.

Citrus Fertilizer Liquids

Liquid fertilizer is typically used during the fruiting phase of a fruit tree. They’re heavier on the nitrogen side of NPK than the others we’ve mentioned so far. With an NPK of 4.5-2.0-4.2, these fertilizers assist in the production of lush growth and contain large amounts of Ca which we know helps reinforce cell walls. Therefore the citrus fruit is much healthier and more supple as a result of using liquid citrus tree fertilizer. And sometimes you’ll find highly effective formulations that are synthetic, rather than organic. 

Slow-Release Citrus Fertilizer

Kumquat tree laden with fruit
If you apply citrus fertilizer annually, you’ll see large harvests of kumquats. Source: locomomo

One benefit of using a slow-release organic citrus fertilizer is that more nutrients get packed into those little granules that dissolve over time. That means there’s enhanced nutrient availability in granular fertilizers and there are often beneficial microbes included. Many of these fertilizers work on several types of fruit trees, so if you have a tropical tree garden with orange, kumquat, and avocado, know there is probably a slow-release formulation out there that will suit all of them. Another benefit of using slow-release fertilizer granules is you don’t have to apply them more than a few times a year. You will need even applications of water during the growing season to adequately release the nutrients, though.

Miscellaneous Citrus Fertilizer

You can fertilize your trees with one of the above types, or you can apply more specific fertilizers that will break down and feed your trees over time. Annual applications of well-rotted compost provide better drainage and water retention, as well as a good profile of nutrients for each tree in your garden. 

Fishbone meal with additions of sulfur, potash, and manganese provides trees with good sources of phosphorous, and nitrogen. These, sulfur, and manganese are nutrients needed for these heavy feeders. Add a little bit of kelp meal to the mix, and you’ve provided iron and other trace elements that help your trees thrive. Interestingly, producers of organic powders source from these materials, but you can apply them yourself if you choose. Chicken manure is another high nitrogen additive that can benefit your citrus trees.

Other natural ingredients you can add include feather meal and alfalfa meal. These both provide trees with large amounts of nitrogen needed for foliage production. Feather meal typically provides fertilization at a rate of 12-0-0 and is a great source of food for beneficial fungi in the soil. Alfalfa does the same at a rate of 2.5-1-1. If you use pellets of alfalfa, they will slowly deteriorate adding aeration to the soil, and they’ll provide food for fungus and beneficial microbial content. 

Additional sprays can come in the form of humic and fulvic acid, which improve soil and assist other fertilizers and plant food by promoting the uptake of organic and synthetic ingredients alike. They in turn improve the quality of fruit as well. 

When to Fertilize Citrus Trees

Orange tree loaded with fruit
For heavy-yielding varieties, you may need to fertilize slightly more often. Source: romaryka

We’ve discussed this to some extent in the last section. But let’s talk about when to apply miscellaneous fertilizer. Compost and mulches, like alfalfa, can be applied at any time of year, but are best used upon planting and in dormancy, in winter and late fall. Soil additives like kelp, fishbone, and feather meal can be added annually before spring growth, and upon planting. The same goes for chicken compost.

Fulvic and humic acid sprays or soil soaks are best applied 1 to 2 times per year along with annual fertilizer. 

How to Fertilize Citrus Trees

Now let’s talk about specific applications to plug into your citrus fertilizer schedule. Once you get a good system going, you’ll have delicious fruits aplenty! Again, remember the best citrus fertilizer is always one that is specifically formulated with organic nutrients AND fits your schedule. Use these two facets to determine which is the right fertilizer for you. 

Spikes

If your chosen fertilizer is in spike form, put these in the ground during the dormant season, shortly before spring. Find the drip line of your tree (or the area 2 to 3 feet outside the circumference of the canopy), and water the area thoroughly. Place the protective cap on the spike, and hammer it in so it’s flush with the ground. You can use multiple spikes for one tree, and up to 4 at one time. Younger trees should have spikes closer to the 2-foot range outside the trunk diameter, and older trees should have fertilizer spikes in the 3-foot range. In containers, place one as far from the trunk as possible.

Sprays

Indoor-grown mandarin tree
Container-grown trees like this mandarin may need more regular fertilization. Source: crouz1

Apply fertilizer sprays in dormancy as well. One thing to note about these is they tend to stain surfaces, so prevent contact with your hands, clothes, containers, and nearby surfaces. Dilute the solution in a spray bottle or hose spray mechanism at a rate of 1 tablespoon per gallon of water. Then spray the entire tree, lightly misting it with fertilizer. Do this 1 to 2 times between December and February. You can also use this fertilizer to correct any nutrient deficiencies during the growing season too. In this case, use 2 tablespoons per gallon of water, applied at 2-week intervals. Mature trees will need a gallon of solution, while younger trees will need less.  

Powders

Most citrus growers fertilize with powdered organic fertilizer. Here, feed your orange, lime, or lemon tree in dormancy. Thoroughly water the area, then evenly spread the powder. For established plants and shrubs, apply the powder at the drip line at 1 cup per 1.5 feet of spread, or 2 cups per 3 feet of spread. For a fully-grown tree, use 3 cups per inch for trunks that are 3 inches in diameter or less. Use 9 cups for a larger tree. Two brands that use natural sources for their powders are Espoma and Bumper Crop. 

If you’re using a shake and apply fruit fertilizer, shake the jug, and apply the powder at the drip line. How much you’ll need depends on the trunk diameter and the tree’s age. It’s important to remember to avoid contact between the trunk and the fertilizer. This powdered fertilizer is useful in container-grown citrus as well as outdoor plants. 

Liquids

Since citrus trees are heavy feeders, you may benefit from plant food that can be applied throughout the season. Enter liquid fertilzers! To help your tree produce more fruit, and promote active growth, use these every 3 to 4 weeks. Simply water the drip line, and then apply the fertilizer from the bottle attached to a hose. Try not to wet other areas of the garden, and focus the fertilizer on your orange or grapefruit tree. Because these are formulated to feed differently, consult the label to determine how much to use. 

Slow-Release

A slow-release fertilizer for orange tree growers is an excellent way to reduce the number of times you have to fertilize. This lessens the workload and simplifies your citrus fertilization schedule. So if you’re wondering when to fertilize lemon trees with slow-release plant food or granular fertilizer, know it will only have to be a few times per year. The best citrus tree fertilizer of this kind is adaptable to an indoor or outdoor tree. In the case of slow-release organic fertilizer for indoor trees, you can fertilize all year round for active growth. An outdoor tree should receive fertilizer in dormancy. Just sprinkle the granules around the area to be fertilized at a rate of 3 tablespoons for every 2 by 2-foot area. Then work them lightly into the soil, and water them in.   

Frequently Asked Questions

Lemon tree with nutrient deficiency
Yellowed leaf edges can be a sign of nutrient deficiency. Source: Keith Williamson

Q: What is the best fertilizer for citrus trees?

A: It depends on how you’re growing the fruit tree and how often you have time to feed it. See above!

Q: When should you fertilize citrus trees?

A: In an outdoor garden, fruit tree fertilizers should be applied in dormancy, while an indoor tree can be fertilized year-round. It also depends on how you garden citrus fruit. Read through to see how different types have different timings.

Q: What is a natural fertilizer for citrus trees?

A: Many citrus fertilizers are also organic fertilizers. The best citrus fertilizers are those that source from natural ingredients like kelp, bone, and alfalfa. Bumper Crop and Espoma are two brands that use natural sources in their formulations. 

Q: Can you over-fertilize citrus trees?

A: You can. Too much fertilizer can weaken the tree overall. Plan out a schedule to apply fertilizer and stick to it. 

Q: Can you fertilize citrus when flowering?

A: Yes! Specifically granular and powder fertilizers can be applied during the growing season.