My favourite growing medium for microgreens
The stuff you use to grow your microgreens in is the second most important aspect of microgreens growing to get right for successful and stress-free grows. The first being your seed quality. Hence today’s blog post.
There are options when it comes to your grow medium and I want to discuss a few of them today, before I tell you which is my fave and why I love it so much!
I’ll just get this out of the way first though - if you’re growing microgreens commercially, I don’t recommend just growing your microgreens in plain water. They’ll grow a bit, but you won’t be anywhere near optimising your yields, which will reduce your crop’s overall profit margins.
You need something for your microgreens’ roots to anchor into and, in my experience, you get a more abundant and healthier crop if it has access to nutrients too. I hear regularly that “seeds have enough nutrients in them to grow to microgreens stage”. It’s true, they do. But they’ll grow faster, stronger and bigger with extra nutrients.
Here are the main grow mediums that I’ve seen microgreens farms throughout the UK using successfully:
1. Coconut coir
2. Hemp & Felt grow mats
3. Compost
I could write a medium-length book on the pros and challenges of each of these mediums, but I’ll keep it brief. I’ve experimented lots over the years of growing on all three of these mediums and here’s what I’ve found:
Coconut coir
Yay!
Nice and fine texture. Really important when sowing the smaller varieties of microgreens seeds.
Very unlikely to have mould spores in it.
You expand it with water before sowing, so it arrives nice and compact in ‘bricks’ and is easy to store. Big advantage if you have limited space and don’t want to or can’t lift heavy things.
It’s a wate product from the coconut industry.
Can be easily composted after use.
But….
Coir doesn't contain nutrients, so you'll have to either use coco coir with added nutrients in it (more expensive) or spend extra time and money on a liquid nutrient and mix it in with your water (if you want to optimise your yield and crop quality).
Generally more expensive than compost for the same volume of medium (but cheaper than grow mats).
Extra time is needed to rehydrate it.
The UK doesn’t produce its own coco coir (too cold and miserable for coconuts!), so it has to be shipped in, increasing it’s carbon footprint.
2. Grow Mats - Felt & Hemp
The main grow mats currently available in the UK are made from felt (a by-product of the textile industry) and, on a smaller scale, hemp (a fantastic versatile and highly sustainable plant farmed in the UK).
You basically cut the mats to the same size as your grow tray, sow your seeds on top if it and just grow as you would on compost or coir.
Grow mats are great at providing an anchor for your plant roots. But, like coir, if you want to optimise your yields, then I’d recommend adding nutrients in with the water. A quick run down:
Yay!
No soily mess! Just a mat that you pop into your grow tray.
Lightweight and easy to store.
Hemp is an extremely sustainable plant (if hemp grow mats didn’t have their downsides, then they’d be my medium of choice for this reason).
More lightweight and less bulky waste after harvesting.
But…
Need to add a nutrient for optimal yields.
They can both ‘technically’ be composted down afterwards, but it takes a long time and if you’re producing alot, you’ll need plenty of space to process it (or a hot compost bin!).
Hemp mats have fly-away fibres that I found were flying about my grow room and landing on the crops when I was preparing trays. Not good. This is best done in a different room.
Hemp mats are still pretty expensive. Felt mats can be cheaper if you buy a massive roll and cut it down yourself, which takes more time.
It’s trickier to get your watering right, as its very easy to waterlog the mats.
A little experiemnt I did a few years ago growing micro rocket on compost (left) and hemp mat without nutrients (right).
3. Compost
Big announcement - peat free compost is my absolute favourite medium for growing microgreens on! I get my best crop quality and yields on compost and it’s what I choose to use in my farm. Using compost as your medium though doesn’t come without it’s challenges. Here’s the lowdown from my experience:
Yay!
Consistently great quality crops and profitable yields (my main priority).
Still cheaper per tray than the above mediums (just!).
It already contains nutrients, so you don’t have to faff adding extra (big bonus!).
Peat-free and made in the UK makes it a sustainable medium.
Microgreens roots break down pretty quickly in compost and if you have more than you can put on your garden, then it’s quite an attractive offer for your local community to come and collect from you (that’s what I do every week - it’s a win win!).
But…
It’s bulky and heavy. And it’s cheaper to buy in bulk! You need a strong back and room to store it, ideally under cover.
Not all composts are the same! Alot of the peat free ones can be quite coarse and woody - great for the garden, but not so great for sowing tiny microgreens seeds into. Also, if a distributor has been storing compost for a while, then it’s quality can be poor and mould spores more prevalent. Always make sure with your supplier that the stock is fresh from the manufacturer. Any longer than 10 months and I’d leave it.
My go-to compost brand in the UK is Melcourts SilvaGrow. It’s consistently great quality and most importantly has a fine enough texture for sowing microgreens seeds into. Like most things, it’s cheaper to buy it in bulk, so if you have the space and funds to do this, I highly recommend it. You can check Melcourts’s website for local stockists. My current compost cost is: £6.74/bag (ex VAT), 34p/tray (ex VAT) (as of Jan 24).
I also know of another couple of microgreens growers who like and use B&Q’s own peat-free compost. So worth a go if you can’t source SilvaGrow.
So some different options to maximise your microgreens production. I personally think coir and compost are the best, but choose the one that suits your situation. I’d love to hear what your preferred grow medium is for microgreens - pop a comment in below and let me know :)
If you’re keen to learn how to get your own microgreens business up and running right now, then here’s my
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5 great reasons for starting a microgreens business in the UK right now
A basic equipment list
A step-by-step guide to growing and harvesting radish shoots and pea shoots, including UK pricing suggestions, seed supplier recommendations and profit margins.
A how-to guide to selling your microgreens to your local community.