Compost Or Coir For Growing Microgreens in the UK
For the past 7 years of running my microgreens business, Nell’s Urban Greens, I’ve always grown my microgreens in peat-free compost. It’s consistently given me great results.
Compost isn’t always a perfect medium to use for everybody though. It’s biggest downsides can be:
The quality deteriorates with age. If your supplier has, or you have, stored it for 9 months plus before using it, chances are the nutrient content in there will have declined.
If it’s been left outside and uncovered either at your suppliers’ site, or your own, it can get soaking wet making it a horrible, soggy, mould-encouraging environment to sow your microgreens seeds into.
It’s bulky to store and heavy to carry around.
The price has increased quite a bit over the last couple of years (November 2024).
If none of these 4 downsides are a problem for you and your business, then I recommend you use peat-free compost for growing your microgreens in, in the UK.
(Peat-free because peat bogs are extremely important environments for the unique biodiversity they support, as well as them being significant carbon sinks. Peat bog destruction releases carbon into the atmosphere, exacerbating the climate crisis. PLUS there are now some fantastic quality peat-free composts widely available in the UK!)
My favourite has always been UK-made, Melcourt’s Silvagrow Multipurpose. It’s got great drainage and has a really fine texture which is perfect for sowing smaller microgreens seeds in. The large DIY chain stores don’t tend to stock it though, so you’d be looking to source it from a local garden nursery. If you want to give it a go, you can do a stockist search on Melcourts’ website, or just email them directly to ask if you have any nearby.
Failing Silvagrow, I know a few growers that are getting good results from B&Q’s own Verve Peat-Free compost at the mo - this tends to have chunkier bits in it though that you might need to pick out before sowing.
Bags of Silvagrow even have a ‘made on’ date on them. Ideally try and source bags that are less than 6 months old. Ask your supplier for the date, if in doubt, before purchasing.
If one of those 4 downsides to using compost is an issue for you though, then you may want to look at an alternative. The most compost-like alternative is coco coir. Coco coir is a by-product of the coconut husk processing industry. A fine material, not too different to the texture of compost and you use it in exactly the same way.
The benefits of using coco coir instead of peat-free compost:
It arrives in a neat lightweight package as a compacted ‘brick’. You then just add water to rehydrate it.
It has a fluffier texture, which makes it a dream for handling and filling trays.
They’re smaller and therefore easier to store.
If bought in bulk from Coco & Coir, your cost for each tray wil be lower (compared to Silvagrow).
Current cost per tray comparison, as of November 2024:
Melcourts Silvagrow - £7.46 / bag (ex VAT, delivered in a 40 bag bulk load) - 37.3p / tray (link is my supplier)
Coco & Coir - £6.81 / 5 kg block (ex VAT, when bought in 6 block bulk buy) - 18.2p / tray
Just in terms of storage, this is 40 litres of peat-free compost on the left and 300 litres of coir on the right (before hydrating)
For this reason alone, I desperately wanted to change my medium over to coir this year! So I did some trials. I’ve done these same trials in the past, but not used the ‘Coco Boost’ version of the coir - the one that has added nutrient balls to it to add some fertility.
The conclusion in a (coco)nutshell - they both worked great! I trialled pea, sunflower, radish and rocket. Really good germination and growth in both mediums for all of these varieties. The slight advantage of the compost though, was it produced a marginally more vigorous and lush growth and increased overall yield for the same growing time in the coir for all varietries trialled. A way to get around this is to grow in the coir for longer to match the yields of the compost (if you have the grow room space for that).
This is what I mean by ‘slight’ difference. Coir grown rocket is on the left and compost grown rocket is on the right. The compost just produces a bushier crop. And this amounted to an extra 50g of rocket on harvest day. You can sell 30g of micro rocket for £2.50 to chefs, £3 direct to the public. So if you’re farming lots of trays, the revenue advantage of growing on the compost can add up.
The main message of this blog post today - both peat-free compost and coco coir are both great mediums to grow microgreens in. I’ve worked with lots of other growers now throughout the UK and Europe, teaching how to run this business, and know from their results aswell that coco coir is a great option if storing, handling and sourcing a quality compost is an issue.
For me, I’m sticking to my Silvagrow for now.
Hi! I’m Amy Wright and I run my own microgreens farm in Leeds , UK.
I also teach people how to set up their own home based microgreens business, specifically in the UK.
If you’re keen to get started growing your first microgreens crops and selling them to your first paying customers, let me teach you how.