The 3 Most Common Microgreens Growing Problems and How to Fix Them
I’m 7 years into my microgreens business now and I’ve stopped panicking when my grows go wrong. It’s definitely a pain, but I’m much calmer about the whole thing these days. It’s partly because I know losing a tray of microgreens, for whatever reason, isn’t the end of the world, but also when you grow the same crops week in, week out, you become a bit of an expert in how to prevent problems occurring in the first place and also what to do to try and minimise their effect once they occur.
Firstly, and most importantly……
Prevention is key!
Your time will always be well spent by doing everything you can to prevent growing problems occurring in the first place. This is why I’ve written this blog post for you today. I want you to have the tools in place to be able to do this, as well as the knowledge of what’s going on if your greens are looking a bit iffy and what to do about it! Let’s go….
Common growing problem #1 - Mould Growth
The dreaded mould on microgreens! Basically if fungus starts growing in your microgreens trays, it will spread rapidly and destroy your plants. It will also look horrible and smell really bad! Microgreens are grown densely, in warm and potentially humid conditions - a perfect combo for mould growth!
Luckily there are some measures you can take to prevent mould from multiplying in your grow trays.
Ensure these 3 things:
1. There are as few mould spores as possible on your seed and growing medium to start with.
Sourcing seed from a reputable microgreens seed supplier is key here. It’s not foolproof, but will certainly give you a head start. I highly recommend Grow Sow Greener in the UK - their seeds are fantastic quality and customer service is excellent - they really want your grows to go well!
Larger seeds tend to be more prone to mould growth such as pea and sunflower. If you’re at the stage where you’re ordering seed in bulk, it’s always useful to get a small sample in first of these varieties and grow a test tray or two (that you’re not relying on for weekly harvest yield), before buying a bulk load in.
Compost tends to have more mould spores in than coco coir and grow mats. If using compost as your grow medium (still my favourite grow medium!), make sure it’s a fresh batch (ask your supplier how long they’ve had it in) and keep it dry (so don’t store the bags outside - I made this mistake this winter :( ). My go to is Melcourts SylvaGrow peat free compost. You can check their website for local stockists.
2. Your grow room environment id kept healthy.
An optimum temperature of 22C, humidity under 60% and plenty of air flow will minimise the perfect breeding conditions for mould growth. I’ve also found at my farm that not cramming in too many trays into my space works wonders for this too. And you can kind of feel it yourself when you walk into your grow room if it’s ‘healthy’ or not. If it feels hot and stuffy, or cold and damp, you need to do something about it. Dehumidifyers work wonders, as well as extraction and or/opening windows and doors.
And finally, get some fans going in there! Air flow is key to stop air stagnating and mould spores settling long enough to start multiplying in your grow trays.
3. Clean equipment.
Bit of a no brainer, but make sure all your kit is super clean. Your grow trays should be washed thoroughly after every grow to make sure any mould in there isn’t left for your next grow. I wrote a whole blog post on tray washing last summer - you’re welcome!
Thoroughly clean and sanitise your harvesting tools, prep table, fridges, racks… If you’re diligent about hygiene, not only will this ensure you’re producing your microgreens in a food safe way, it will also help you have stree-free grows too!
If you do notice you have mould on your seed and/or the grow medium (this is usually apparent when they’re first taken out of germination), you can try and prevent further spread by pulling out the affected area - seeds, shoots and compost. This doesn’t always work, but you might be able to save some of your crop if there’s only a small amount of mould in there. Obviously this isn’t ideal and is a last resort to try and save a tray.
Always implement your prevention methods first!
Common growing problem #2 - Damping off
Damping off is also a result of a fungus attacking your plants. So firstly, ensure you’re doing everything listed in the previous section on mould growth. Damping off can cause your microgreens shoots to just suddenly collapse and it’s heartbreaking when it happens! One minute, everything’s growing amazingly, then the next morning, boom, they start to shrivel up and die :(
It’s a hard one to control and I’ve even had problems with it over the last few weeks whilst introducing my new coriander and rocket crops for the summer.
Once you’ve ticked off the 3 prevention methods above and damping off is occurring frequently for you, try these 3 measures:
1. Sowing your seed less densely - this will allow more airflow between each shoot and reduce those stagnation conditions.
2. Try a different compost, or a different medium altogether. You may just be using a particularly spore heavy batch.
3. Don’t over water. Some of your more delicate varieties such as broccoli, rocket, kale, coriander… can become overwhelmed by too much water, as damping off is encouraged by damp! Water these crops sparingly and only when your bottom tray is completely dry.
Some smaller trays of micro rocket I’ve been trialling recently. The one on the left was sown 2 days before the one on the right. As soon as damping off takes hold of these delicate shoots, it quickly spreads throughout your tray. You still may be able to harvest some crop if this happens, but just make sure all the stems are white and robust when harvesting and not brown and floppy. For your next tray, clean everything thoroughly, re-set, and go again using the prevention techniques listed above.
Common growing problem #3 - Uneven or Poor Germination
To be as financially efficient as possible in your microgreens business, ideally you want every single seed to germinate. That way, you’re optimising your yields every time and in turn your profit margins. So what to do if these are below par?
A poor germination rate is usually due to either your seed or your technique.
1. Technique - Firstly ensure that you’re following the correct process of germinating your particular variety:
✔ Larger seeds usually need a soak in water overnight to kickstart the process.
✔ By stacking and weighting most varieties, it will speed up the process and encourage even germination.
✔ Don’t let seed dry out in germination.
There’s a link below to my Starter Guide which explains how to grow two different microgreens crops, including the exact techniques of how to germinate your seed properly.
2. Seed
Not all seed of the same variety is the same quality! Different suppliers source their seed from different suppliers, that have come from different fields and sometimes from different countries. It took me a while to learn this when I first started my farm! I just assumed I was doing something wrong when my grow success changed suddenly for a particular variety.
If you want to dive deeper into seed sourcing in the UK - here’s a blog post all about it :)
If you’re getting your germination technique right (see above) and you’re getting less than 80% germination (it should be around 95%), then you may have poor quality seed. If this happens, here are your options:
✔ Order another small sample of that variety from a different supplier and see how they do.
✔ Ask in our Farm Microgreens UK Facebook Group for recommendations of current good quality batches.
✔ And if you do find you have a poor seed batch, take photos of poor germaination rates and/or any mould present, send them to your seed supplier and politely ask for a refund or credit note. And it’s worth mentioning that this doesn’t happen often, especially if you’re sourcing from a good UK supplier like Grow Sow Greener, but when it does, it’s important seed companies know about it.
Mastering your growing techniques through problem prevention will enable you to consistently grow excellent quality microgreens! And if you can grow excellent quality microgreens, week in week out, then the whole process will be much more enjoyable, streamline and selling them will be an absolute breeze!
Wishing you a lifetime of problem-free microgreens growing!
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.