Compost 101 for container gardens

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Composting is a great way to improve your container garden, save some money, reduce your carbon footprint and do something good for the environment.

But wait! If you’re picturing a huge yard with big compost bins … or walking out to the back acreage with a pitchfork to turn the pile … never fear.

You don’t need a farm or even a big yard to make your own compost. Just like container gardening, it’s totally possible in small spaces!

And if you’ve found this post, that probably means you’re interested in learning about compost and how to make it.

So read on for all the basics to help you understand the magical world of compost! (It really is pretty awesome!)

If you’re looking for recommendations for bins and other composting containers, check out my post about small compost bins for container gardening!

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white kitchen compost bin full of food waste on a blue table

Composting definition

The act of composting is to recycle plant material in a way that speeds up the natural decay process. The composting process creates an ideal environment for organisms and fungi to process the plant material.

Composting involves combining brown and green organic matter, as well as food waste (like vegetable scraps and kitchen waste), in a pile or bin. In scientific terms, when managed in a “hot composting” manner, this creates the ideal environment for aerobic (using oxygen) decomposition.

What is hot composting?

Hot composting involves layering organic materials, keeping them watered and turning regularly to heat up the pile and encourage microbes and other organisms to decompose the plant matter.

Steady moisture levels and high temperature are both needed to create a hot composting environment. With the right balance, you can get finished compost in about a month.

What is cold composting?

“Cold composting” is similar but more common in larger yards because it has to sit for a long time.

Cold composting involves piling organic material and then letting mother nature take over, without turning, adding water, etc.

This is an anaerobic process, and the temperature doesn’t get high enough to kill some pathogens and weed seeds.

It takes a lot longer to produce usable compost — often a full year or two — but it’s an easy hands-off way to get some finished compost if you have the space for it.

Benefits of composting

Once it’s finished decaying, aged compost is used to enrich new soil. It’s a powerful fertilizer that adds microbes, nutrients and beneficial organisms.

It improves soil structure and provides organic fertilizer (assuming you used plant material that wasn’t previously treated with herbicides or other chemicals).

Environmental benefits of composting include reducing food and yard waste, improving soil, conserving water and reducing methane emissions from landfills.

Gardeners love this “black gold” because it gives a slow release of nutrients throughout the entire growing season. Many gardeners mix some compost in when potting the plants, then side dress or apply compost tea throughout the season for nutrient boosts.

What you can compost

Make sure you have a good balance of green material (grass, leaves) and brown material (dry leaves, straw, paper).

Remember, any plant matter or yard waste you compost should be chemical free.

If you treat your lawn with chemical pesticides or herbicides, don’t use those grass clippings in your compost. The chemicals can interfere with the organic process in a compost pile — and can end up harming your container plants.

Green things to compost

Grass clippings
Used coffee grounds
Perennial and annual trimmings
Animal manure (NOT pet waste)

Brown things to compost

Dried grass clippings
Twigs and bark
Straw and hay
Corn stalks
Sawdust
Newspaper and unbleached coffee filters
Pinecones
Toilet paper tubes without glue

Food scraps

Leftover veggies
Vegetable scraps
Peels and cores
Egg shells
Melon rinds
Corn cobs

What you can’t compost

Plant matter

Anything that’s been chemically treated (see above).
Be careful about seedy weeds, especially if you’re cold composting. Those weeds might pop up in your containers next season.

Food scraps

In general, animal products should not be composted. They take much longer to break down, and they attract pests in the meantime. This includes dairy products, meat, bones and cooking grease. (Unless you’re using the Bokashi composting method, in which case animal products are okay.)
While eggs fit into the animal product category, many people do compost egg shells. They’re high in calcium and break down more quickly than bones. You can wash them first to deter pests.

How to care for your compost

Successful hot composting requires some care and attention.

While cold composting is more of a “set it and forget it” approach, hot composting needs consistent moisture and movement to heat up the pile and create the best environment for our microbe friends.

Follow the manufacturer instructions for whichever type of composting bin you choose, but two general things to keep in mind:

Turn the compost

Turn the pile, rotate the bin, or stir the compost every few days with a garden fork or trowel, to make sure everything is mixed together well.

This aerates things and gets the new items you’ve added down deeper to where the microbial action is.

Turning the compost regularly will also help keep the smell down.

Keep it watered

Add water as needed to keep things moist but not wet.

Green items are fresher and wetter (like coffee grounds and fresh grass clippings), so you can always add more of those if your compost runs a bit dry.

If you go too far in that direction and it all gets soggy, simply add more brown items to dry things back up a bit.

hands holding compost from a worm bin with red wigglers — Red wigglers are the key to a successful worm bin

How to use compost in your container garden

Good news! Small space composting is totally doable, especially with smaller containers like worm composters, plastic storage bins and 5-gallon buckets.

A bokashi bucket or compost tumbler makes it possible even for apartment dwellers (and container gardeners without a big backyard or much space) to create your own rich soil amendment.

Countertop compost bins are small and affordable, and they’re the easiest way to collect kitchen waste for adding to your compost.

Reminder: If you’re looking for recommendations for bins and other composting containers, check out my post about small compost bins for container gardening!

Mix compost into potting soil

Compost is a great way to amend your potting soil, whether you make your own or purchase a bag from the store. This will give your plants the best start by knowing exactly what you’ve added.

I usually mix in a few handfuls when planting.

Potting soil is designed to have good soil structure for container plants, to optimize moisture control and root growth. So don’t add too much compost or you risk compacting the soil.

Side dress containers with compost

Especially when you’re starting your pile and don’t have a lot of useable compost, you can try side dressing your container plants.

Side dressing simply means to spread some compost around the edge of the pot. This allows the nutrients to seep into the soil as you water.

Do this monthly throughout the season for a steady supply of fertilizer.

Make compost tea

Compost tea includes liquid strained from compost and a mixture of other ingredients and fertilizers.

It improves soil health and water retention, loosens dense soil, and adds beneficial organisms.

And you don’t need a huge quantity of compost to get it started! Even just 2-3 cups of compost is enough to make some potent tea.

This article about DIY compost tea from Eartheasy recommends combining the follow ingredients in a 5-gallon bucket. Follow their instructions for mixing and straining.

Non-chlorinated tap water
2 cups fully finished organic compost
1 tablespoon unsulfured blackstrap molasses
1 tablespoon liquid kelp fertilizer
1 teaspoon liquid fish fertilizer

When you’re ready to use the tea, dilute it to at least 1:4 ratio tea to water. Use that diluted mixture in a watering can to water at the soil level or by foliar feeding.

Now that you’ve been through Compost 101, you know all about the definition of compost, what materials can be composted or not, and how to compost in small spaces. Have you tried it? Let us know your favorite tips in the comments!

Compost 101 for container gardens