How to grow microgreens commercially during the winter in the UK
One of many brilliant reasons to run your own microgreens business is that you can grow and sell fresh food all year round! I always take orders right up until Christmas week at my farm (micros are great on festive canapes!), then start back in early January. Fresh, nutritious food for your customers during the cold season AND a consistent year round income for you.
But despite being possible to grow these crops all year round, we have very changeable seasons in the UK, which will ultimately affect your growing - even your indoor growing. As we now move into autumn and the colder season, I want to discuss this in today’s blog post.
Key point to remember:
Lower temperatures, followed by declining light levels are the two main environmental factors that will affect your microgreens growing during the autumn and winter months and these are what you need to think about and focus on in your own grow space.
Where to grow your microgreens during the winter (from October onwards in the UK).
The short answer is – somewhere warm! Most of us grow microgreens indoors all year round, which can benefit from the central heating being on anyway in the winter if you’re growing in your house. Some grow outside in greenhouses, polytunnels or out-buildings during the milder seasons of spring and summer, which is great and very do-able. However, unless you have a heated, and well-insulated outdoor space, I wouldn’t recommend growing microgreens commercially outside during the winter in the UK (from around October to April).
In low temperatures (sub 15C) and decreasing natural light levels (< 10 hours/day), your microgreens will still grow, but they will slow right down and you’ll see many more inconsistencies with the growth quality and grow cycle times. A nightmare if you’re growing them to regularly sell to customers.
My indoor grow room 2017 - 2020 at Nell’s Urban Greens. The radiators warmed it during the day when needed, as did a dehumidifier. I also used supplementary LED lighting to extend the light levels to 12 hours a day.
How warm does it need to be?
The more consistent you can get your temperatures in your growing space, the more consistently your microgreens will grow. This is particularly important when you’re growing commercially, as you will have deadlines (harvest and delivery days) and will need to know exactly how long the grow cycle is for each crop in your own grow room.
An ideal temperature is 22 C. The majority of crops love this temperature and you can turn them around fast when it’s this warm. In reality, most houses aren’t this warm during the winter and that’s OK. You’ll just need to work out the grow times for whatever your temperatures are. I’d recommend trying to increase your grow room temperature though if it doesn’t regularly climb over 18 C during the day.
I ran my farm commercially for the first 3 years in the conservatory at the back of our house (see above!). So there was lots of glass – great for natural light, not so great for keeping temperatures consistent. I didn’t heat it during the night (to save on energy) so in winter, temps fluctuated from 3C over-night, to 30C during the day when the sun came out! Not ideal, but it worked. Kind of. I had to keep tweaking my grow cycles to fit in with the changing weather, but it definitely enabled me to establish my business and continually grow it during this time.
What I want to get across in this post is that there are ideal conditions for growing microgreens commercially during the winter, but it’s still doable without perfect conditions too, especially if you’re just starting out and want to keep your start up and running costs to a minimum.
Conditions for germinating your seed during the winter
Getting the conditions right for germinating your microgreens seeds is pretty important – and more so in the winter months. Your aim is for every seed in your tray to start germinating at the same time. That way, they should all grow at the same rate and then be much quicker and easier to harvest if they’re all at the same length on harvest day. If your grow room gets cold (sub 17 C), I suggest finding a warmer place for germinating. This might be a smaller room in your house, different to your grow room. Germinating seeds definitely need the warmth. I used to germinate mine in a kitchen cupboard because I didn’t have any other space to stack a load of grow trays in the early days!
Be careful not to over-heat them though either – this can lead to excessive mould growth, dying off of seeds and your grow medium drying out. So don’t put them on radiators! And be careful if choosing to use heat mats for this process.
Insulation – the energy saving essential!
Insulate, insulate, insulate! One of the most effective ways of spending any cash and effort in your business at the beginning (or at any point if you haven’t done it alrdeay!), is focussing on making your grow room as well-insulated as possible. As energy prices begin to soar in the UK, the last thing you want is to be paying for is expensive heat energy that is just getting lost to the outside instead of being used to grow your plants. Fill any gaps, consider an extra insulation layer on your walls, anything you can do to stop heat escaping during the colder months will be time and money well spent.
*And I’m not ignoring the current energy price soars by the way! We definitely need to think about and adapt to this in our microgreens businesses, so it will have a full post to itself next week*
Humidity
As with any time of the year, the humidity of your grow room needs to be controlled somewhat. Growing lots of plants in the same space, and closely together, will definitely raise the humidity in the room. If the humidity gets too high, water droplets will form on the canopy of your greens, weighing them down and eventually turning them to mush if they can’t get rid of it. Warm, humid conditions will also speed up any mould growth in your trays and regular, excessively high humidities can damage walls and furnishings in the room - not great anywhere, but especially in your house!
Control this by using a dehumidifier. One unit should be enough in a small space (I use two in my 6m x 3m grow room for 80 trays/week) and running a dehumidifier also has the added benefit of emitting heat as a waste product – ideal to help warm chilly grow rooms in the winter! Realising this myself was a game changer in my new, current grow room. I made sure that it was very well insulated and I’ve never had to put the heating on. The dehumidifiers have always heated it sufficiantly all year round (2 winters in) and running both of them uses half the electrcity of the underfloor heating system!
There’s no need to get overly obesssed with humidity levels, but around 50 - 60% is a good aim. The more crops you have in the space, the more you’ll need to control the humidity. You can buy a cheap hygrometer and thermometer-in-one online to keep your eye on these too parameters. These work well.
And just remember, as a rule of thumb - if you feel comfortable in your grow room, then so will your plants! If you walk in there and it feels like Leeds’ Tropical World, you’ll need to bring that humidity down!
Air Flow
Again, as with any time of year – keep air flowing through your growing space using fans. Not necessarily on the end of every grow shelf, but one or two oscillating floor fans should be enough to keep that air moving through your room.
If air is moving, any mould spores are less likely to settle and grow in your trays, particularly during the germination stage. Good airflow also aids efficient plant transpiration.
Using fridges during the winter
A final word on fridges – ensure they’re working properly and don’t end up freezing your harvested microgreens when temperatures start to fall outside! I used to use a fridge in our non-insulated outside garage to store my microgreens in before delivery and they froze to mush one night!
If you’re setting a temperature, 5C is sufficient for microgreens refrigeration. You can use a fridge thermometer to keep this in check.
And my last top tip for this week - don’t place your punnets of harvested microgreens too close the back of the fridge. Again, they might freeze to mush!
Now go hunker down, keep you and your plants warm and enjoy growing, selling and eating your fresh microgreens all winter long!
My UK Microgreens Business Starter Guide will provide you with a basic equipment list of what you’ll need in your grow room to get started and run your microgreens business all year round!
You’ll also get:
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 and profit margins.
A how-to guide to selling your microgreens to chefs, restaurants and your local community.