How Do You Know When Compost Is Ready?

Composting is the magical process of taking select garbage and waste products, chucking them into a pile (or composting box), and the fertilizer gnomes turning it into grade-A compost – or so many are led to believe.

In reality, composting is a series of events involving these waste products’ decomposition (and even digestion) until all you have left is a pile of insect and bacterial poop.

When Compost is ReadyPin

But while Mother Nature has been composting since there was anything to compost, humans are still fairly new to the idea, and it’s easy to become confused or frustrated.

And that brings us to the subject at hand: How long does a compost pile take to do its job, and how do you know when this wonderful plant food is ready to use?

This can be a very complicated question to answer due to many variables.

Let’s look at some of those variables, ways to test if your compost is ready, and how to harvest it.

How Does Composting Works?

Before we get into identifying when compost is finished, it’s important to understand how the process itself works.

There are four phases to the composting process, and each has an important effect on the final product.

Mesophilic Phase

Sometimes referred to as cold composting, this is the initial state your compost pile will be in.

During this stage, the brown (carbon) and green (fresh) materials are broken down by an orchestra of bacterial, chemical, insect, and worm activity.

Here, the smell of rot tends to disappear, making it difficult or even impossible to identify individual materials.

Thermophilic Phase

Also known as hot composting, this second stage further refines the compost into a fine blend of indistinguishable ingredients at a far more rapid pace.

Achieving this state of decomposition requires a lot of extra work, so it rarely happens in home composting.

However, the extra effort destroys a wide range of pathogens and any seeds in the compost, making it safe and sterile.

Cooling Phase

This phase is especially necessary if you didn’t skip the thermophilic phase but still has an important role to play even if the compost never reaches temperature.

This stage will result in your compost pile only having half the volume as it was started.

It also dries the mix out a little and ensures it’s ready for use.

Curing Phase

This final stage is another one people often forget about, as it’s very similar to the cooling phase.

However, proper curing helps ensure the best possible quality for adding it to your garden and greatly decreases the chance of any partially composted chunks.

How Long Does Composting Take?

This is going to be the question that stumps most people.

How long it takes for composting depends upon the method (and materials) you use as well as how much effort you invest into the process, so let’s look at how these two variables can affect composting time.

Timing Depends on Method and Content

There are actually many different composting methods, and what you add to your compost can also have a huge effect.

For example, shredded cardboard will compost in as little as 2 to 3 months, while using the lasagne method takes around a year.

In fact, many composting methods will take approximately 1 year to complete as long as you aren’t throwing whole banana peels or other large pieces directly onto the pile.

It should be noted that adding too much water to your compost can result in the need to add more brown material, which will slightly extend the overall composting time.

Timing Also Depends on Dedication

As with all good things, the more effort you put in, the better the results.

In the case of composting, you can skip two of the phases if you don’t mind a vastly substandard product that may transmit disease or produce weeds.

Likewise, if you make a huge compost pile, it will (naturally) take far longer to compost than a small pile.

Running food waste through a blender or otherwise breaking it down into small pieces can mean the difference between efficient composting and a glorified landfill that can take ages even to get started.

And then there’s turning the compost.

This important step (especially during the thermophilic phase) helps to ensure even composting and efficient breakdown of the material through micro and macro agents such as insects, earthworms, and bacteria.

You can turn the compost in as little as every 2 to 3 days if the middle has reached the golden temperature zone of 100° to 120° degrees Fahrenheit, but you can also wait a week or two between turnings.

Just remember that every delay in turning equates to a delay in the final product.

Signs Your Compost May Be Ready

There are several signs your compost is ready to harvest, including:

  • The pile has shrunk to roughly half its original size.
  • The compost smells like dirt, not like garbage.
  • You can’t find identifiable traces of anything you added when you sift through the compost.
  • The compost is dark and crumbly to the touch like good forest dirt.
  • The compost has cooled off (if you’ve followed the entire process).

The Radish Test and Problems With Unfinished Compost

This is a cheap and effective way to test your compost, as radishes not only germinate quickly but are highly sensitive to the many problems that unfinished compost can cause.

Simply take a bit of the compost and plant some radish seeds.

If they germinate into healthy seedlings, your compost is ready.

However, if the composting process is incomplete, several side effects will harm or kill the radishes, including:

  • The appearance of diseases or pests
  • Suffocation due to the compost using up nitrogen and oxygen to continue breaking down
  • Burns from the higher temperatures caused by continued decomposition
  • Failure to germinate due to the presence of phytotoxins

To ensure failed radishes result from the compost, be sure also to have a control group to compare growth rates to.

Harvesting Compost

Harvesting is a little more complicated than simply scooping out all the compost, but not by much.

You’ll want to remove any unfinished composting material (a lot of people like to use ½” inch screens to sift out any unfinished chunks).

The fully composted material can be harvested for your garden.

Once you’ve removed the finished material, dump any unfinished compost back into your bin or pile and begin adding fresh layers of material on top to restart the composting process.

JOIN Our FREE Plant Care Newsletter 

By entering your email address you agree to receive a daily email newsletter from Plant Care Today. We'll respect your privacy and unsubscribe at any time.