Can You Use Leca And Soil Together?

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Yes, you can use soil and leca together. Leca can be used as an alternative to perlite as it can add aeration to the soil and holds water.

What is leca?

Leca is an acronym, I just hate typing LECA and I’m lazy. I have a full article about what leca is and why we use it here, but in short, it stands for lightweight expanded clay aggregate. They basically cook clay until it pops like popcorn.

The most common way to use leca with houseplants is to use it as a substrate for keeping plants semi-hydroponically. I wrote an ultimate guide to keeping plants in leca (it’s very long so you may need to go and get a cup of tea before starting on that one) but that’s geared towards semi-hydroponics.

This article is about using it as a soil amendment.

Advantages of using leca

Leca is sterile

Especially if you, er, sterilise it. This is one of the main reason people go into semi-hydro – you can boil leca before you use it, and be guaranteed that you’re not introducing beasties like fungus gnats into your house. The same cannot be said for things like orchid bark.

Leca doesn’t break down

So you can keep on reusing it forever. This is an advantage, but I don’t want you to think that using soil amendments that do break down (again, like orchid bark) is a disadvantage. Bark breaks down and leaches nutrients into the soil, which is helpful to some people. It really depends on your setup, and you can definitely use both together.

Leca doesn’t attract bugs

One of the main reasons people go into semi-hydroponics is that reduction of bugs. Note that I said reduction, not elimination. Leca is easy to clean and sterilise.

Leca adds aeration

Lack of oxygen is the driving force behind root rot, so adding leca to your soil can help combat the bacteria that cause it. Not only does leca form air pockets in the soil (especially if you get the more uneven stuff), but it contains loads of tiny holes that allow oxygen to flow through the soil.

It also absorbs water, which can reduce the water in soil, which allows for better air flow.

Leca is a cheap filler

The sceptics among you might be thinking, many of those properties can be said of perlite and I do agree BUT perlite can be harder to get hold off in larger quantities. The price of both leca and perlite varies a weird amount but I’ve consistently seen that large (20l) bags of leca are cheaper than the same amount of perlite*.

Except that a garden centre to me once did 20l bags of perlite for £19.99 but I have NEVER seen that price repeated, or anywhere else do anything remotely similar. Felt like a glitch in the matrix, tbh.

How to use leca and soil together

Use leca as a bottom layer

I use the leca-as-a-bottom-layer in my terrariums, because unlike gravel, it’ll absorb water if you accidentally go overboard with the watering can. I prefer either a fogger or a spray bottle to water my terrariums, but if you choose a watering can, a layer of leca on the bottom might be better than gravel.

You can also use leca as a bottom layer on your plant pots – I like to pick out the chunkier bits and use them to cover the drainage holes. Water can still drain away, but you’re less likely to lose all your soil.

NB using leca in the bottom of your plants pots does NOT negate the need to have drainage holes.*

*In my opinion. If you’re unsure how you feel about drainage holes, read this article. If you’re a staunch I-don’t-need-no-drainge-holes person, I salute you. I’m too lazy to want to worry about overwatering my plants.

Use leca as a top dressing

A compelling reason to put rocks on top of your soil for outside plants is that it will stop your plants from blowing over. Do NOT use leca for this. The L in LECA stands for lightweight. You’ll just make a mess.

There are a couple of good reasons to have a layer of leca on top of your plants though:

  • It can stop the soil from drying out so quickly, especially if you mist it frequently, or put a humidifier near it.
  • It can deter cats from digging in the soil (check your cat won’t eat it)
  • It looks quite good, and is a great option for those of us that hate it when all the perlite rises to the top

Mix leca throughout the soil

This is a solid option that admittedly I only use in one situation (when I run out of ‘proper’ soil) but it’s a solid workaround that I have zero options with.

When it comes to ratios, it really doesn’t matter, you can do anything between 100% soil and 100% leca, just be aware that anything over 50% leca will require more nutrition, so if you’re a sporadic fertiliser don’t stray over the 50/50 mark.

Also, if you have a higher leca to soil ratio you can end up with a puddle of muddy water at the bottom of your pot which will be a breeding ground for fungus gnats and other beasties. You might have to wait a

Half an hour or so after watering and then tip out any excess water.

My ratio usually depends on how much soil I have, but I tend to go for a solid 70% soil, 30% leca mix.

Final thoughts

Thought my reasons for mixing leca and soil together are questionable (I mix my own soil, usually run out half way through repotting and cba to mix any more) it works really well, and can be a cheaper alternative (and less messy) to perlite.

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