How to put roots in my compost bin | Step by Step

To add roots to your compost bin by shake off excess soil, chop roots into small pieces and mix them in with other compost ingredients. Water the roots in thoroughly and in 3-6 months they will break down to make rich compost. Compost the roots of legumes, comfrey and annual flower and avoid any weed roots with seeds, runners or store bought root vegetables which can take over your compost bin.

Step by step guide to putting roots in a compost bin

Follow these easy steps to safely add plant roots to your compost bin.

  1. Check for any seed pods attached to plant stems
  2. Shake off as much soil as you can from the root system
  3. Chop roots into small pieces
  4. Mix roots in thoroughly
  5. Water the plant roots into the compost
Add plant roots to compost bins or bags mixed with other materials.

Check for any seed pods attached to plant stems

Before adding roots to your compost bin, check that there are not seed pods still attached to the stems. This is important if you are adding weed roots as the seeds may re-sprout in your compost or soil. If the plant does have seed pods, it is best to put the weeds into your green bin or turn them into compost tea.

If you are hot composting weed roots with seeds can be added but make sure you get your compost up to hot composting temperatures. For more on hot composting methods, check out my previous article on ‘why compost heaps get hot’.

Annual flowers, comfrey and soft annual weeds can be added to compost. Avoid root systems that can grow back easily like mint, potatoes and grass runners.

Shake off as much soil as you can

Before adding roots to your compost bin, shake off as much garden soil as you can. The soil can be added back to your garden beds but can slow down the composting process if too much is added to your bin.

Chop roots into small pieces

Chop long or large clumps of roots into smaller pieces before adding to your compost bin or compost bag. This will help them to break down quicker as they can be spread out through your compost in amongst other composting materials.

Mix roots into compost thoroughly

Plant roots are a carbon rich ingredient for your compost so mix them through with green materials such as food scraps and coffee grounds. Mixing plant roots in with fall leaves, straw, sugar cane and old mulch will help them to break down in around 6 months time.

Water roots into compost

After adding plant roots to your compost, water them in well using a garden hose or watering can with added seaweed solution. This will help to grow more bacteria in your compost which will break down the plant roots.

Plant roots can be a very dry ingredient so it is important to add extra water when you mix them into your compost.

How long roots take to break down in compost

Most thin plant roots will take anywhere from 3-6 months to break down in a well balanced compost. Turn your compost pile regularly to mix the ingredients, add extra oxygen and support microorganisms which will break down the organic matter.

Root systems that should not be composted

Here are my top plant roots that you should not be composted.

Store bought potatoes

Store bought potatoes can quickly grow roots if they are left for too long in your cupboard. It is best not to add these to your compost because they can add diseases and often do not grow potatoes well. They can quickly take over your compost instead of breaking down.

Mint roots

Mint roots are quick growing and will easily re-sprout in your compost pile. You may find that your compost is quickly taken over by the fast growing mint if you add the roots to your bin.

Avoid adding mint roots to your compost bin.

Weed roots with seeds

Fast growing weeds like bindweed are easily transferred throughout your garden if you add them or their roots to your compost. Seeds can easily hide in amongst root balls so it is best to get rid of these roots altogether and not add them to your compost.

Grass roots with runners

Grasses that have running roots like Buffalo or Couch grass should not be added to your compost pile. They can quickly re-grow and become a problem in your compost bin. Even a single inch of root can re-grow if it has a growing node so it is best to avoid adding these to your compost bin.

Buffalo grass will grow quickly in your compost so avoid adding roots to your mix.

Roots that are more than 4mm thick

Large root pieces will take a long time to break down so it is best to shred them with a mulcher before adding them to your compost. Large root pieces can be chopped up carefully using a sharp shovel to increase their surface area to help them to break down quicker.

Large tree roots are best turned into mulch and laid on top of garden beds like bark chips.

Best plant roots to compost


The roots of legumes like peas, beans and lupin are fantastic to compost as their small roots can trap nitrogen from the air in nodes. This will break down and be released in to your compost giving it a nitrogen boost.

Legumes including peas are great root systems to add to your compost.


Comfrey grows deep roots which absorb nutrients from the soil and stores them in its roots and leaves. Adding comfrey roots to your compost will increase the breakdown rate of the organic matter and add extra nutrients to your soil.

Comfrey will absorb nutrients deep in the ground and store them in stems and roots.

Composting the roots of annual plants

Annual plants are usually removed each year as they die off and their root systems are great for compost. Annual flowers will have small root systems that will break down easily adding extra organic matter to your compost.

Annual flower roots are great additions to your compost pile.

Composting plant roots – summary

Plant roots are a fantastic carbon rich material to add to your compost. Remember to avoid any root systems that might be carrying weed seeds and chop larger roots into small pieces. Microorganisms will quickly break down thin plant roots and legumes will add valuable nitrogen to your compost mix.

Happy composting.

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