The Ultimate Guide of Citrus Fertilizer

 Fruit trees consume an extraordinary amount of nutrients. I always treat them as hungry little monsters, especially if you are used to the light fertilizing for indoor leafy greens. The amount is minimum compared to citrus kept in containers.

If your climate is mild enough for growing citrus trees in the ground, lucky for you, you do not have to strictly follow a feeding schedule and carefully choosing the right feeding product. This is not to encourage you to leave your citrus tree alone, of course, just to say the care is easier. You can use strong synthetic fertilizer with less concern of root burn, inserting fertilizing spikes at the beginning of the season and forget about it, or if your soil is rich in nutrients, you can fertilize only when you see a need.

Many of us live in colder zones where citrus must be kept in containers. The most common mistake made by new citrus parents is to think that raising citrus in containers is not much different from raising it in the ground. Actually, the difference is huge.

I keep my citrus in a container and give it regular dose of fertilizer.

Below are some common myths about fertilizing citrus in pots：

Got premium potting mix with fertilizer. No need for extra.

Citrus in containers can never get enough from your premium potting mix, even if your soil package says this product has fertilizer mixed in. Reminder: Your citrus is a fruit tree. Most of the home growers get the dwarf version, but still, it is a fruit tree. When the potting soil manufacturer develops their products, they mix in some fertilizer that is adequate for the average potting plant’s need. The amount of fertilizer needed continuously over the growing period, at the fruit tree’s scale, is off the chart compared to that.

Too little fertilizer will starve your citrus, resulting in fruit drop, leaves yellowing and dropping and no flowers. Too much fertilizer is worse in destroying the citrus roots, which may lead to losing your plant. To prevent fertilizer burn, you are recommended to avoid using synthetic fertilizer at full dose and avoid using fertilizer spikes. Organic citrus spikes are okay if you can find no other options, but you will have to be careful in monitoring your plant’s growth. The “insert and forget” fashion does not work for pot-grown citrus as you instead of Mother Nature, are responsible to adjust the dose in various growth stages. If you have to use spikes, I would suggest crush it to granular and apply.

The only time you can loosen a little about root feeding is when you first bought citrus. The little green pellets mixed in the original pot is the fertilizer applied in commercial citrus farms. These green helpers will support your citrus for three months maximum. After the three months, nutrition deficiency will show up quickly without extra feeding.

Fertilizing citrus is all about NPK.

In addition to macronutrients (Nitrogen, Phosphorous and Potassium), citrus need micronutrients (Mg, Iron, Ca, Zinc…) to thrive. Sourcing the right micronutrient supply for citrus is a headache in Canada. We are well known for being overcharged with very limited choices. Many good fertilizers that provide micronutrients are not available in the Canadian market or are only offered online at a ridiculous price. The frugal practice is to use home-made organic fertilizers that provide at least some micronutrients, if not all. I use compost tea and worm casting, for example. If lacking certain micronutrients, there would be telling sign on your citrus leaves. The downside of this practice is obvious: You can only fix the problem when it shows up.

An ideal choice would be to use a comprehensive product that comes with everything. If you have your hands to Foliage Pro, fertilizing is easy. Mix some with every watering and foliage spray from time to time, you will see the difference like many other citrus home growers do.

I need a fertilizer high in P and K, because I want my citrus to flower and bear fruit.

I was surprised to find out the ideal NPK ratio for citrus is 3:1:2, which tells me citrus is a heavy nitrogen feeder. Its evergreen foliage needs consistent nitrogen supply all year round – I assume you are going to move the citrus indoor during cold seasons, and in that case it would be summer to the plant. With citrus, what I found is that you would have to make the foliage happy first, before ever thinking about flowers and fruits. Only after the lush green has put on a show, the tree will think about when it’s time to give blooms. It is a warning sign if your citrus blooms with minimum leaves. In survival mode, citrus produces offsprings under the death threat, so be careful seeing flowers without leaves.

There is a concern that the high percentage of nitrogen is going to suppress the flowering, which does not hold for citrus. Let’s say you apply a high potassium fertilizer in 1:6:3, the citrus will only take 0.33 percent of phosphorus as limited by the 1 percent of nitrogen, and the rest will go wasted. Applying an imbalanced rate of fertilizer that is high in P can suppress the flowering, and causing the risk of over-fertilizing.

To help fellow growers, I have summarized a chart of good citrus fertilizers available in the Canadian market.

Dyna-Gro Foliage-Pro	9:3:6	Organic with complete micronutrients	$$$	Liquid	Available mostly online
Osmocos Plus	15:9:12	Organic with complete micronutrients	$$$	Granular	Available online
Miracle Grow Water Soluble Evergreen & Acid Loving Plant Food	28:10:10	Synthetic	$	Crystal	Available in stores and online
Jobe's Organics Fruit & Citrus Fertilizer Spikes	3:5:5	Organic with micronutrients	$$	Spike	Available mostly online
Jobe's Organics Fruit & Citrus Tree Granular Fertilizer	3:5:5	Organic with micronutrients	$$	Granular	Available mostly online
Evolve Organic All-purpose Fertilizer	3:1:2	Organic with micronutrients	$-$$	Liquid	Available mostly online