I prefer adding compost to container plants to give them a good supply of nutrients. It’s effortless to do once you know the procedure.

You can add compost to container plants when preparing the soil and once the plants are growing. Adding compost to the potting mix helps refresh old soil and keep plants growing healthy for many years. Add compost to the potting mix every month when growing vegetables.

I’ve written all the steps you need to follow to add compost to your container plants. I’ve also written about when and how much compost you should add to the soil.

1. Mix compost into the potting soil

The first time you can add compost is when preparing the potting soil for your container plants.

You may have either prepared your own potting soil by mixing perlite, vermiculite, and peat moss. Or you may have purchased the potting soil from a store.

Spread out a layer of newspaper or plastic sheet on the ground. Or you can use a wheelbarrow if you have one.

Pour the potting soil on this surface based on how much you need for your container plants. Then add 25% to 50% of compost to the potting soil and mix it well.

Please keep adding a little water when you’re preparing this potting soil and compost mixture. You want it to be moist but not soggy.

Then you can add this potting soil to the container and grow plants in them.

I have an idea that can help if you want to save the compost as it can tend to be a bit expensive. You can use a little compost instead of mixing 25% or more into the potting soil.

Instead, you can add the potting soil to the container. Dig a hole in the center of the potting soil where you would grow the plant. Now add a couple of inches of compost to this hole and then place the plant in it.

So you use a little compost instead of mixing in a lot of it with the potting soil.

2. Add compost on top of potting soil

The compost you added to potting soil will provide the nutrients and beneficial organisms to the plant. But the nutrients will only last about 6 weeks before they are used up or leach out due to the watering.

I recommend adding compost every month to the container once the plant has started to grow. This will help the plant get a constant supply of nutrients.

If you have put mulch on the soil, make sure to separate it before adding the compost.

Don’t dig into the potting soil when you want to add the compost. You risk damaging the roots and the beneficial organisms in it.

I suggest removing a little bit of the topsoil and then adding an inch of compost to it. Then you can cover the compost back with some of the soil.

You can avoid disturbing the soil and adding an inch of compost on top of the soil itself. When you water the plant, the nutrients from the compost will leach into the soil.

If you have little compost, you can add it near the base of the plant rather than cover the entire potting soil. Just keep some space, so the compost does not touch the plant.

I recommend that you cover the layer of compost with mulch. This is organic material such as grass clippings, wood chips, dried leaves, or hay.

The mulch will protect the compost and help keep the temperature regulated, so the moisture remains in the potting soil longer.

Once you have added the compost, make sure to water the potting soil well till it drains from the drainage holes at the bottom.

3. Decide how much compost to add to potting soil

I recommend not adding more than 50% compost to the potting soil when preparing it. And adding an inch or less to the top of the soil after the plant is growing.

If you have very little compost, you can add a few inches near the roots when planting. Add only a little mulch near the base of the plant once it is growing.

You would think that the more compost you add, the better it is for the container plant. But this is not true, and more compost can cause issues for the plant.

If the potting soil too much compost, it will have a very loose texture. This will drain out water fast, and your plant may suffer from underwatering.

The loose texture will not provide a stable structure to the plant. So as the plant grows taller, it may fall over.

4. Pick the best time to add compost to potting soil

Some people prefer spring as the time to do this as they grow a new batch of plants. But I think there’s no particular time to do this.

The best time to add compost is when you’re preparing the potting soil to grow the plant. And add in a little compost every few weeks as the plant needs some nutrients.

compost packet
Packet of compost I used for my plants

I would not recommend adding compost to the top of the soil only after germination, and the plant is a few inches tall.

I would also not recommend adding compost when there is a chance of rain because it can wash away the compost.

It’s best to add the compost to the potting soil before watering the plant in the morning. Then the watering will help the nutrients seep into the potting soil.

5. Find out how often to add compost to potting soil

If you’re growing resource-hungry plants such as vegetables, I recommend adding compost every month to the top of the potting soil.

If you’re growing flowering plants, you don’t need to add the compost as often. You can add it 2-3 times during the growing season.

If you make compost tea, you can frequently add it to the potting soil because it is diluted. You can add a few spoons to your watering can when watering the plant.

You must check the potting soil bag if it already contains some compost or fertilizer. If it does, you may not have to add the compost, at least when preparing the potting soil.

6. Choose the best ratio of compost to potting soil

I recommend adding between 25% to 50% compost to the potting soil when preparing it for your container plants.

This ratio is sufficient to give the plants a good supply of nutrients and beneficial organisms for a few weeks.

7. Choose the compost to use for container plants

I recommend you use compost that has been strained through a screen. This compost will be a fine powder that will mix well with the potting soil.

You can attach a mesh hardware cloth to a wooden frame to make such a screen. Then sift the compost through it.

You don’t want the compost to clump up and not distribute evenly in the potting soil. This will not spread the nutrients well enough for the container plants.

The best compost you could use is the one you prepared yourself. You know what organic materials you used, and it will be of the highest quality.

But most people won’t have space or time to make their own compost, so it’s OK to buy some from the store. But make sure it has some quality certification, so it provides your plants with the required nutrients.

Further Reading

You can learn all that is required to start your own container garden including starting seeds, watering, mulching, fertilizing, pruning, and harvesting. Check out the post below,

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