How To Fertilize Outdoor Potted Plants & Containers (2024)

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Fertilizing potted plants is very important in order to keep them growing their best. In this post, I’ll tell you why it’s so important, talk about the different types of plant food, and which are the best. Then I’ll show you exactly how to fertilize containers, including when, how often, and how much to feed them.

One of the biggest mistakes that new gardeners make is breezing over the importance of feeding their container plants. If you’re new to growing in containers, then you might not realize how important fertilizing potted plants really is.

Feeding container plants can be a confusing and intimidating topic for newbies, I know it was for me! So it’s just easier to ignore it, right?

Don’t worry, you don’t need to be a chemist to figure out how to fertilize a potted plant. You just need to understand a few basic things. My goal in this detailed guide is to break it all down, and make it super easy for you.

Table of Contents

Why Fertilizing Potted Plants Is So Important

Quality container potting soil has a lot of great ingredients for growing healthy potted plants. But those nutrients won’t last forever. They get used up by the plants, and also wash out of the pots a little bit each time you water.

Feeding container plants is even more important than for those growing in a garden plot. Since their roots aren’t in the ground, they can’t go deeper or spread out to find all the nutrients they need.

Containerized plants are completely dependent on us to provide everything that they need in order to grow and thrive. So that’s why it’s so important to fertilize them on a regular basis throughout the growing season.

Using Chemical -vs- Organic Fertilizers For Feeding Potted Plants

Before I jump into the specifics of feeding container plants, I want to talk briefly about synthetic chemicals -vs- organic fertilizers. Chemical fertilizers give us instant gratification, but can cause long-term harm to plants.

They feed the plant rather than feeding the soil, which means your plants will need to be fertilized more often. They’re also made of salts, which can quickly build up in the soil, and cause major damage.

It’s also very easy to burn plants when using synthetic fertilizers, which is a very common problem for containerized plants. So, when it comes to fertilizing potted plants, it’s always best to use natural, organic fertilizer.

Organic fertilizers feed the soil, and naturally give the plants exactly what they need to grow their best. They don’t need to be applied as often, have minimal risk of fertilizer burn, and result in a much healthier container garden.

Some great organic potted plant fertilizer options

Best Organic Fertilizer For Container Plants

Manufacturers make it easy choose the best fertilizer for potted plants at a glance by putting numbers on the packaging. But what do those numbers mean?

Those numbers represent the amount of each of the three most important ingredients that plants need to grow their best. Nitrogen, phosphorous, and potassium (N-P-K for short).

The reason for the numbers is that certain types of plants require different amounts of these nutrients. Here’s how to choose the right fertilizer for feeding potted plants…

Best Fertilizer For Container Vegetables

Vegetables need a lot of nutrients to stay healthy, and produce the best crops for us. So it’s especially important to fertilize vegetables in containers.

For the purpose of choosing the best fertilizer for them, let’s put all of our vegetables into two main categories: flowering and non-flowering…

Flowering vegetables are those that need to bloom in order to produce fruit. Examples are beans, squash, tomatoes, peas, and peppers. These types of veggies need fertilizer that’s high in phosphorus (P), so choose one with a larger middle number.

Non-flowering veggies are those that we harvest for the leaves or roots. Examples are lettuce, kale, carrots, spinach, radishes, and chard. Choose a fertilizer that’s high nitrogen (N) for these types of veggies. The first number should be the largest of the three.

Related Post:Guide To The Best Fertilizers For Vegetable Gardens

N-P-K numbers on a potted plant food bag

Best Fertilizer For Flowering Container Plants

It’s also very important to feed your flowering plants throughout the growing season so that they will continue to bloom. Otherwise they can fizzle out half way through the summer, and stop producing flowers.

The best plant food for potted flowers is a higher phosphorous (P) fertilizer. That means the center number on the label is largest.

Liquid Fertilizer -vs- Granular Fertilizer For Containers

Now that we know which type of fertilizer to use for feeding potted plants, the next question is whether you should use liquid or granular (aka: slow release)?

Each has their own unique benefits for fertilizing container plants, so the short answer is to use both! Below I’ll discuss the differences between the two, and show you why it’s best to combine them.

Liquid Fertilizer For Potted Plants

The biggest benefit of using liquid fertilizer for potted plants is that it’s absorbed very quickly by the plants. But the downfall is that it doesn’t last very long.

You can buy liquid fertilizers pre-mixed, as a concentrate that you mix with water, or as tea bags so you can brew your own. Here are a few examples of fantastic liquid fertilizers for potted plants…

Slow Release Fertilizer For Potted Plants

On the flip side, granular fertilizers release their nutrients over time, so they aren’t immediately available to the plant. But that means they feed the plants longer, and you don’t need to apply them as often as liquid fertilizers.

There are tons of wonderful products out on the market these days. You can buy them for general use, or specifically for different types of plants. Here are some excellent options…

Applying natural slow release fertilizer for potted plants

When To Fertilize Potted Plants

You can fertilize potted plants at any time during the day, but never fertilize a plant that is dehydrated or drooping. Fertilizing potted plants that are under stress can harm or even kill them.

So, always check the soil before feeding container plants. If the soil is dry, or the plant is drooping, give it a good drink of water, and then wait a few hours before adding fertilizer to the pot.

Using organic liquid fertilizer for plants in pots

How Often To Fertilize Potted Plants

You should feed your potted plants regularly throughout the entire growing season. For best results, always follow the instructions on the label, because products can differ.

But, generally speaking, slow release granules only need to be applied 2-3 times per season. So, add them to the soil when you first plant your containers, and then again once or twice during the summer.

You can apply liquid fertilizer every 2-4 weeks. Some gardeners will use a weak dose each time they water so they don’t have to remember to stick to a schedule. In this case, be sure to add about 1/4 – 1/5 of the recommended amount to your watering can.

How Much Fertilizer To Use In Potted Plants

The amount of fertilizer to apply to potted plants depends on the size of the pot, and the product you’re using. So, rather than give you any specifics here, I recommend following the directions on the package.

Most labels will tell you how much to use for the size of pot your plants are in. So it’s important to follow those guidelines, and never add too much fertilizer to potted plants.

Even though the risk of burning them is much lower when you use organic fertilizers, it is still possible for some. Plus, overdoing it doesn’t have any additional benefit the plant, and will just end up costing you more money.

Fertilizing containers with organic slow release granules

How To Fertilize Potted Plants

How you fertilize depends on whether you’re using liquid or slow release. Below I will give you basic guidelines for how to apply fertilizer to potted plants. But you should always read the instructions on the label of the specific product you’re using.

Adding Slow Release Granules To Containers

Sprinkle the recommend amount of granules (based on the size of your pot) evenly over the top of the soil.

Then use a hand fork to gently loosen up the soil, and mix it in. Water the soil well to activate the granules.

Applying Liquid Fertilizer To Potted Plants

First mix the recommended amount of liquid fertilizer and water in a watering can.

Then simply pour the mix into the soil as if you’re watering the plant. You can also put some into a spray bottle, and spray it on the leaves for foliar feeding.

Mixing fertilizer for container plants into the soil

Fertilizing potted plants is important in order to grow healthy, productive, and beautiful container gardens. Once you get the hang of it, and see how much better everything grows, feeding your container plants will become second nature.