How to fertilize a lemon tree in a container
Lemon trees are the perfect fruit trees for containers. They are relatively easy to grow and smaller compared to other citrus trees. We’ve been designing our backyard garden and I’ve been aching to get one.
I finally snagged an Improved Meyer Lemon tree! I potted him up in one of my favorite planters next to my kitchen door.
Hi! I’m Mr. Meyer
I’ve grown lemon trees both in containers and in-ground. Goodness knows I’ve made my share of mistakes, but on the other hand I’ve grown loads of lemons.
Over the years I’ve never had to buy any lemons for our lemon bars, lemon meringue pies and lemon tarts. (Yes I bake lots…) and also for our marinades and dressings. This tree was a super prolific eureka lemon tree that gave me massive lemons 👇🏼
One thing I’ve learned though - it’s that container lemon trees need a tad bit more attention. In general, you need to be aware of your watering and fertilizing and how they affect the tree. Problems can escalate more quickly in a container so try to be super observant.
Remember that because the container is a closed soil system, the tree will be completely dependent on us for water and nutrients. The tree cannot absorb nutrients or water from the native soil if it needs something.
Watering is pretty straightforward - citrus likes lightly moist but not wet soil. Let the water drain out the pot so it flows through the drain holes to get water throughout the pot. I cover with Kellogg’s Gromulch on top to protect the soil surface during the hot days.
Fertilization is key when growing a container lemon tree.
Fertilization amounts and scheduling will be a little different than an in-ground tree. Most packaging I find for fertilizers don’t really explain how and when to feed your container lemon trees.
I think if you learn just a little about the tree’s needs and what the fertilizers can provide, you’re much more likely to have a healthy tree with lots of fruit.
So in this post I’m going to walk through how I:
pick the correct fertilizer for a container lemon tree,
calculate the amount to apply,
schedule how often I feed my lemon trees.
A quick refresher on fertilizer:
Alright, I don’t want to get too chemistry up in here 🤓 but it’s good to know some basics about fertilizers before which one is best for your lemon tree.
Fertilizer provides nutrients for the plants that it is unable to obtain by itself. I actually read that without fertilizers, the planet’s food production would go down by more than half! So we, as gardeners, supply those nutrients to ensure a happy and healthy plant.
The nutritional components of fertilizers can be classified into two major groups: macronutrients and micronutrients.
Macronutrients are your big hitters - plants will need these in large amounts. Examples of macros include: nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca), and sulfur (S).
Micronutrients are still essential but needed in smaller amounts. Examples of micronutrients include zinc (Zn), manganese (Mn), chloride (Cl), iron (Fe), copper (Cu), nickel (Ni), boron (B), molybdenum (Mo).
Each plant has favorites nutrient combos, so let’s get into lemon trees in particular.
How to choose a fertilizer for lemon trees
There are different types of fertilizers and fertilizer-ers (people who do the fertilizing. Yes, I made that up).
Generally, you can take two routes.
The first route is to mix and match custom nutrient levels based on your specific growing environment.
You use soil composition, watering schedule, rainfall levels, leaf tissue analysis etc. to determine the best nutrients for your trees. In fact, this is what commercial growers do.
It’s kind of like going to the drugstore and picking out individual vitamins, such as iron, calcium, and fish oil. If you know you are anemic, have low bone density, and would like a bigger fish brain, and all your other nutrients are provided by diet, your vitamin selection is on point. 👍🏼
This is a highly custom approach and you have a great chance of growing a fantastic looking tree with lotsa lemons, if you know your growing conditions and calculate your numbers right.
The other route is using balanced citrus fertilizer, which is like a multivitamin for your trees!
Balanced fertilizers contain high amounts of macronutrients, a blend of micronutrients, and sometimes other supplements.
Companies determine the nutrient levels and so these can vary from brand to brand. They typically take fairly generalist approach, e.g. “Fruit, Citrus, and Nut Trees”. There are probably thousands of varieties, so sometimes you need to double check the labels to make sure the nutrient amounts are what you’re looking for to feed a citrus tree. (We’ll go over that below.)
I prefer a balanced citrus food. This has worked most of the time and I’ve only needed to supplement nitrogen when I was growing avocados. Honestly, it’s just easier and I’m a little lazy. It may be more expensive, but I figure I’m paying for the plant scientists’ lemon tree knowledge.
What nutrients are required for optimal lemon tree growth?
For lemon trees (and citrus for that matter) the macronutrient that we’re going to be paying the most attention to is nitrogen. The tree is highly dependent on it for all matters of growth, from flower formation to fruit production and leaf growth. It needs other nutrients too, but in smaller amounts than nitrogen.
You’ll see people saying that citrus are “greedy feeders'' and “hungry trees”. This means that we need to feed them a steady supply of nitrogen throughout the growing season.
This means that we should fertilize our lemon trees right before flowering in the spring until the start of fall.
Citrus goes dormant in the winter and fertilizing too late will promote new growth that can be damaged by cold temperatures.
Citrus is really obvious when it doesn’t get enough nitrogen. They’ll start to develop yellowing leaves, usually going from old leaves to new leaves. Prolonged nitrogen deficiency decreases their fruit production, small tree size, and drops leaves.
I mean think about it...nitrogen is a chemical signal of good, fertile soil to a citrus. Low levels of nitrogen signals that its food may not be readily available. In response, the tree tries to conserve resources by remaining small, not producing fruit or extra leaves. It’s entering survival mode.
Since nitrogen is the most important, we’re going to base our fertilization amounts and schedule based on nitrogen using a balanced fertilizer, meaning we’ll give plenty of the other nutrients just fine.
How to read a fertilizer bag
We’ll use those three numbers on the balanced fertilizer bags to do our calculations. They stand for the percentages of nitrogen, phosphorus, and potassium (N-P-K) contained in the formulations by weight.
For instance, check out the citrus-tone bag pic above. That has the numbers 5-2-6. This means that there is 5% nitrogen, 2% phosphorus, and 6% potassium by weight.
Meaning, if we were to apply 1 lb of fertilizer, there will contain:
0.8 oz (16 oz * 0.05) of nitrogen (N)
0.32 oz (16 oz * 0.02) of phosphorus (P)
0.96 oz (16 oz * 0.06) of potassium (K)
Now specifically for citrus, I see varying ratios all over the place, but for the most part gardeners recommend a ratio of 5-1-3 or thereabouts. Meaning you’ll want to look for a fertilizer that has N-P-K in that ratio. (So 5-1-3, 10-2-6, 15-3-9, etc.)
I’m using Citrus-tone for the most part, which doesn’t really follow this convention of 5-1-3 ratio. I have some extra bone meal for this purpose though, which I’ll supplement this growing season if I need more nitrogen. Bone meal is an excellent source of organic nitrgoen.
Check out my nitrogen 😎
How to calculate the amount of fertilizer based on nitrogen levels:
Nitrogen amounts for each tree is going to depend on (among other environmental factors) the type of citrus and size of tree. In general, lemons need more a little more nitrogen than grapefruit, oranges, and mandarins.
According to the University of California’s Agricultural and Natural Resources citrus recommendations, our lemon trees should the amounts of nitrogen listed in the table below.
These are the amounts of nitrogen that your tree needs *per year*
| Age of Tree | Approx. Nitrogen amount per year |
|---|---|
| 1 | 2-4 oz. |
| 2 | 1/4 lbs |
| 3 | 1/2 lbs |
| 4 | 3/4 lbs |
| 5 | 1 lb |
My tree is a year old. Using the Citrus-Tone exclusively, I would follow these calculations. Remember the ratio is 5-2-6, so
5% by weight nitrogen
1 year old tree needs 4 oz total for the year
1 lb contains (16*.05) = .8 oz
4 oz per year / 0.8 = 5 lbs total per year
I could weigh this, but Citrus Tone gives me a shortcut for volume in that that 3 cups of fertilizers is approximately one pound.
That means I would have to give this one tree 3 cups * 5 lbs = 15 total cups per year.
When should you fertilize your lemon tree?
Remember, we want to provide a steady supply of nitrogen throughout the growing season. This should start right before blooming and stop at the end of summer/beginning of fall. We don’t want to encourage growth that may be hurt by cold temperatures.
Normally, the total amount of nitrogen or balanced fertilizer should be split up between 3-4 applications. For a normal growing season, this equates to about every 6 weeks or so.
But because our lemon trees are in a container, some of the nutrients will leach out. This is normal as we water, and the tree may not have been able to pick up the fertilizer in the soil as quickly. In this case, I typically spread my fertilization into 5 smaller applications.
Remember, I need a total of 15 cups of citrus tone per tree per year. With 5 feedings per year, I would need 3 cups per feeding. I have selected the following dates for my trees throughout this growing season:
March 10
Apr 24
Jun 8
July 23
Sept 6
In the midst of summer, I tend to forget while harvesting tomatoes and such, so I always put these dates in my google calendar as a reminder.
I hope this helps you figure out your lemon tree fertilizing and have happy lemons.
