Can You Compost Leeks?

By Veronica Fletcher | 
Last updated on April 3, 2021

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Leeks are a staple ingredient of many delicious dishes. A close relative of garlic and onions, leeks are part of the allium family of vegetables. If you find yourself with more leftover or unused leeks than you bargained for, you might be wondering what you can do with them and whether they can be composted.

So, can you compost leeks? Yes, leeks can be composted in moderation. It’s important to note that leeks have quite a pungent aroma when decomposing, so may not be best suited for urban composting. Also, you should never compost leeks with leek rust.

Can you put leeks in your compost bin?

Leeks can of course be composted, but there are a few situations where you may want to think twice before adding them to your compost bin.

One such situation would be if you’re composting in an apartment. Like other vegetables in the allium family, leeks can emit quite a foul-smelling odor when they’re decomposing. If you are adding leeks to your compost, bury them as deeply as possible (12 inches is a commonly suggested depth) in your pile to minimize smells escaping.

Another thing to be mindful of when your composting leeks is their pH. Leeks have a pH between 5.49 – 6.17, meaning they’re fairly acidic. On its own, this isn’t an issue, as you can easily mix other materials into your compost bin to offset the acidity of the leeks. But it could become a problem if you compost a lot in one go.

Composting whole leeks

If you try and compost whole leeks, you’ll find the body of the leek will take significantly longer to break down compared to the leaves.

Chopping your leeks before composting speeds up the decomposition process

The best piece of advice we can give is to chop down the leeks into small chunks before adding them to your pile. This advice also holds true for absolutely anything that you plan on composting.

Can you compost cooked leeks?

If you’ve already cooked your leeks and want to compost the leftovers, whether they can be composted will depend on what they’ve been cooked in.

If you’ve used a lot of oils or fats to cook the leeks, we’d recommend only adding a small amount to your compost bin.

Leeks are often cooked in oils or fats

Oil is not an ideal addition to your compost pile, mainly because it’s slow to decompose and prevents oxygen from entering the pile.

We have a dedicated article on composting oil if you’re interested in learning more.

Can you compost leeks with rust?

No, you should never compost leeks with rust. Most home compost piles don’t get hot enough to kill the spores that cause leek rust. If you add diseased leeks into your compost pile you risk infecting your next lot of crops when you use the compost.

Heating up a compost pile is possible, but it’s not easy, and even experienced composters can struggle. With diseases like leek rust, we always prefer to be safe over sorry and leave the affected plants out of the pile.

What is leek rust?

Leek rust is a fungal disease that can infect all alliums, including leeks, garlic, onions, and chives. You can usually spot if a leek has been infected with rust by looking at its leaves.

Leek rust causes orange ‘blisters’ on the leaves of infected vegetables

There’s no need to dispose of the whole leek as it’s still perfectly edible and safe to eat. Only the affected leaves should be removed and disposed of before cooking.

One tip I’ve seen mentioned by a few fellow composters is to burn the leaves of the infected leeks before later adding the ashes to your compost. Ash is alkaline so can help balance out the acidity of any fresh leeks in the bin.

Can worms eat leeks?

In general, worms don’t like to eat leeks and will avoid them until they’ve completely rotted down. During decomposition, leeks release sulfur compounds leading to a ‘rotten egg’ smell that can hang linger for months. Not pleasant for us or for the worms.

Worms are sensitive creatures, and strong or odorous foods can overwhelm them. The issue with most worm bins is that the worms are confined and can’t easily move away from something if they don’t like it. By adding foods like leeks that the worms would prefer to avoid, you’re creating an unpleasant environment for them. This can mean they don’t work as quickly and so your worm farm will be less efficient.

Can you compost leeks in an apartment?

If you’re an urban composter, you may be wondering what your options are for composting leeks in your kitchen or apartment. The main issue with this is the potential for odors.

Bokashi is a relatively new method of ‘composting’ food scraps and has gained a lot of popularity in recent years due to its odorless system. Unlike traditional compost bins, Bokashi bins can easily deal with all sorts of items that may be difficult to traditionally compost, including leeks and even meat and dairy.

If you’re considering investing in a Bokashi bin (highly recommended), I recommend the SCD Probiotics All Seasons Indoor Composter (link to Amazon). It comes with everything you need to get started so is great for beginners.

For more information check out our review of the best bokashi bins.

Summary

The key to composting is to ensure your pile always has a good balance of green and brown materials. If you follow these principles, you won’t go too far wrong, whatever you decide to compost.

About Veronica Fletcher

Veronica has a passion for all things eco-friendly. After growing up on a farm in Ireland, she went on to study Chemistry and Environmental Sciences. Veronica has also volunteered in many sustainability roles, including conservation efforts in Bangladesh and teaching Environmental Sciences to schoolchildren in Kenya.