If you're looking for a finer grade charcoal have a look at KiwiChar BioChar >

HortiChar is horticultural charcoal. This is the coarse grade. Being a natural product the size of the charcoal chips varies quite a bit in the bag, but the larger chunks average 1.5cms to 2cms. You'll find a mix of fine to chunky size chips due to the nature of charcoal, so expect some fines and smaller grit size pieces in the mix.

One 500ml bag is the recommended amount to create 5 litres of DIY potting mix, based on a 10% ratio (see below for how much to use). Or if you prefer a higher percent, get the same grade in the 1L size here > to create a 20% ratio for 5 litres of potting mix, or 10 litres mix using a 10% ratio.

How much charcoal should be added to potting mix?

Horticultural charcoal is a popular additive when creating your own custom potting mix blend. How much you add depends on the grade. The finer grade charcoal (like BioChar), should make up about 5% of your entire mix. I normally aim for 2% myself, which is about 250mls of fine grade as part of 5 litres of potting mix. A chunkier or coarser grade can make up as much as 20% of your final mix (I usually go for around 10% for mine). To make 5 litres of potting mix you might like to include 500mls to 1L of coarse charcoal as one part of making 5 litres of potting mix.  

What are the benefits of charcoal for plants?

DRAINAGE & OXYGEN

The coarser grade helps keep water moving down and out of the pot, and the irregular shape and highly porous nature of charcoal increases air space in the mix, reducing the risk of diseases that prefer low-oxygen environments, such as root rot.

PROTECTION

Charcoal is naturally anti-microbial, with a high capacity to absorb impurities and toxins from the soil including harmful bacterial and fungi such as root rot. This is called keeping your soil 'sweet'. In closed environments without drainage, like terrariums and pots without drainage holes, charcoal is used to help keep harmful pathogens to a minimum. 

HEALTH & GROWTH

Charcoal retains the nutrients plants need to fuel growth, increasing nutrient availability when roots need it, improving soil fertility to help grow healthier plants. Being highly porous it's also a great home for beneficial soil microorganisms which also helps boost soil and plant health. 

Safety first

Exactly the same as you should with all substrates, including potting soil and soil amendments: When handling charcoal, wear gloves and wear a mask then wash your hands after potting up. Charcoal can be dusty, so wearing a mask is recommended. It's ideal to dampen charcoal and keep it moist when working with it.  

Please note

500mls is a volume measurement at the time of packing, not based on weight, and contents may settle over time.