I’ve made a lot of mistakes figuring out how to grow microgreens, and this article will help you learn from them.
Read on to find out a few of the things you’ll want to avoid on your microgreens adventure!
Letting Fruit Flies and Insects Destroy Your Crop
To prevent fruit flies and other critters from infesting your microgreen grow you’ll need to take a couple of simple precautions.
- Re-use soil
- Let temperatures get too high (above 70 F, 21C is pushing it)
A big no-no for microgreens is reusing soils. You need as close to sterile as you can manage. Sterile is almost impossible with soil, but you can make sure you’re using fresh soil (or a growing pad) for each new tray.
High quality soil will be carefully composted and mixed at high temperature to pasteurize (kill most negative organisms).
Re-used soil can be full of insect eggs, mold, decaying root remnants, and other unpleasant things.
Growing in Plastic that’s not Food Safe
“Food-safe” means the plastic is designed to be in contact with food for prolonged periods. It won’t degrade, or leech chemicals into the food that are harmful to humans.
Not all plastics are created equal. You might not like plastics at all, or you might love them for their convenience, either way, it’s important to understand that they’re not all created equal.
Mistaking Root Hairs for Mold
To the untrained eye, root hairs look a lot like mold! Roots send out tinier roots that look like a white fuzz, just like mold. The way to tell if you’re looking at root hairs and not mold, the root hairs will evenly cover all of the seedling roots. Mold usually breaks out in a specific spot (or two, or three), and spreads from there.
Spiderweb looks like mold.
For some great pictures and more info on this, check out my article here:
How to Prevent Microgreen Mold and Tell it Apart from Roots (Links to Article)
If your root hairs turn grey or any color other than white, you might have root rot, which is probably caused by seed density, but could also be from over-watering.
Seeding too Densely
Seeding too densely – Sure the seeds will germinate, but the microgreens will complete more for light than grow healthy – Also can lead to disease issues because of holding too much moisture and no airflow.
Wrong seeding density. Seeding density varies a lot, between 1 ounce and almost 10 ounces per 10” x 20” tray. Check out my seeding density calculator for recommendations by type.
Clumped up seeds, especially on a growing pad or mat can cause seeds and roots to decay. If seeds are trapped underneath other seeds they get too wet, and start to promote mold growth. This mold can spread upwards and cause healthy nearby microgreens to weaken and fall over (damping-off).
Growing at the Wrong Temperature and Humidity
The best humidity for Microgreens is Low! Aim for under 50%, and closer to 25 or 35% if you can. If you keep humidity down, and dial in your watering, you’re most of the way towards a problem-free grow.
Smell can give a good hint at your humidity, if there’s no smell coming off your microgreens, your humidity is probably in a good place. If humidity is too high you can buy a dehumidifier to control it.
Higher humidity will precipitate in the canopy of your microgreens. The leaves will be wet, and create perfect conditions for mold.
Keeping your temperature at or slightly below room temperature gives you the best conditions for growth. A temperature of 68 ° F or 20 °C is ideal. Too hot and microorganisms will quickly spread in the soil if your humidity is low, or in the soil and leaves/stems if humidity is high. It might be tempting to
Using the Wrong Growing Medium or Soil
Some microgreens are very difficult to grow on the wrong medium. For example mucilaginous seeds are best mixed with other seeds, grown on hydroponic mats, or seeded sparsely. Growing medium matters.
A lot of microgreens home growers are on plant-base diets. If you or your customers are strict Vegans, it’s important to know that some growing mediums aren’t 100% vegan. Casein (a mammal-milk derived protein) is often added to the latex used to bind coconut coir (and some other fibers) together into growing mats.
A good hint that a mat has latex is the smell. Latex smells like rubber! Think of a hot tire in the sun. But latex doesn’t necessarily mean the growing mat has Casein in it, it just increases the probability. Armed with this information ask the grow mat manufacturer if you’re growing strictly for vegans.
Soil is natural and easy, but can cause also cause problems. Some health departments and commercial kitchens prohibit soil (or anything that looks like soil, like soil-less mixes and coconut coir) from being in areas where food is prepared. If you’re planning on selling microgreens that are still growing in the tray, this is something to keep in mind.
Overwatering & Causing Mold
Overwatering means giving your microgreens more water than they need.
Unlike a potted plant that has drainage holes and sites on a saucer, your microgreens are probably trapped! If you’re growing in a solid container, or have a solid nursery flat underneath your perforated one, the microgreens could be swimming in water if you over-water.
Mold and other microbial issues can be caused by overwatering and having standing water that goes stagnant. Often people will recommend adding fans, and this can be a solution if your humidity isn’t too high. The fans will move air around and dry out the canopy of the microgreens. But the best solution is to water a little less at a time, and a little more often.
If you soak your seeds, and have a good blackout cover (like another grow tray), then you only need to moisten the growing medium. Too much water can work against you. The blackout period will trap all the moisture in, and you won’t need to water until you expose them.
Once the seedlings see the light, they’ll quickly green up. At this point it’s a good idea to water from the bottom, but more on that in the next tip!
Top Watering – Blasting Seeds & Soil Everywhere
Top watering, or watering from the top isn’t necessary and often causes more problems than it’s worth.
But what’s the alternative?
Bottom-watering! Bottom watering means getting the water down to the root and growing medium, without getting the stems and vegetation wet. You can do this by growing in a tray with drainage holes, that’s nested inside another tray. You water between the trays. You’re bottom watering!
If you’re going to be out of town for a couple of days, you can add a bit of extra water so your bottom tray acts as a reservoir, but you’re risking mold. Better to just get a friend, family, or a neighbor to stop by and water your microgreens on your regular schedule.
I had this problem once where I could not for the life of me figure out why my microgreen trays were growing lopsided. I ended up rotating them every couple of day and the problem went away.
What I eventually realized was that my shelving was out of level!
I was sub-irrigating (watering between trays) and the water was pooling more on one end than the other. The one end was well watered and grew great, the other end was water-starved.
Take a bubble-level to your shelving and you’ll avoid this problem from day 1. It’s easy to shim most shelves by putting something under the legs or supports to level it out.
Not Sanitizing Tools and Equipment
You bang the tray upside down when you’re done harvesting. All the soil falls out, maybe a few straggling roots are left behind, but what harm will they do?
Well, if you’re in a hurry next time you’re planting, and just throw your soil into the tray and starting growing, you’d be surprised how big of a difference it makes!
Any roots, seed hulls, or soil leftover from the last crop will put mold and microorganisms that much further ahead. I lost a lot of trays to this when I first started growing and I was figuring everything out.
I hope you’re smarter than me and get into the routine of cleaning everything sooner rather than later.
Using too much soil
Maybe you ended up buying 2” deep microgreen trays to start out. I used greenhouse nursery flats, and it seemed natural to me to fill them right up to the brim at first!
I was using almost three times as much soil as I use now.
So learn from my mistake, a loose 1” of soil is all you need. The roots will have plenty of nutrients to absorb, and will make a nice tight mat of roots.
If your compost pile is higher than your house (like mine), this tip will definitely help out.
Buying too much equipment when starting out
For some people it’s tempting to dive right in, take the plunge, and buy all kinds of things right from day 1. For other people they think they need a whole bunch of things, so they hold off even getting started for fear of missing something critical.
Whichever camp you’re in, you might be surprised how little you really need to get started.
All you really need are some seeds, and a good bag of indoor (pest free) soil.
Almost any container will work for microgreens (be careful with watering if it doesn’t have drainage). You probably already have scissors that will work harvesting. And everything else is pretty much optional, especially to start.
Not soaking seeds
A little bit up the page I said all you need are seeds and soil (or another growing medium). But that’s not quite true! You also need a little bit of water, and some knowledge.
It’s obvious once you’ve tried it out how much of a benefit it makes (particularly for larger seeds like sunflower and pea), hindsight is always 20/20.
Soak seeds for 12-24 hours. Soak for too long and they can drown, too short and they won’t fully hydrate. Hydration starts the clock for growing, so you want everything nice and evenly hydrated from the start.
I tested 6 hour vs 12 hour soak times for sunflower seeds:
How long should you soak sunflower seeds for microgreens? (Links to Article)
For more information on how to store seeds (and some cool tips you might not have thought of), check out my article:
How to Store Microgreen Seeds for Long Shelf-life & Vigorous Germination (Links to Article)
Buying the Wrong Seeds, Including Vegetable Seeds
This is especially critical if you’re selling microgreens. You need to buy seeds that have been stored and labelled specifically for human consumption. Certified organic seeds doesn’t just mean fungicide and pesticide-free, it usually means a few more important things too:
- The seeds are tested for Salmonella and E.Coli by an independent lab (Mumm’s sprouting seeds does this, for example)
- Rodent and bird-proof storage is used from the day the seed is harvested, to the day it’s shipped to you.
- Manures and additives used on the fields where the seeds are harvested have been composted to reduce and eliminate harmful microorganisms
Treated seeds that are non USDA often have fungicides and other chemicals which help them keep longer, and grow more consistently without problems. That’s fine if you’re growing a whole plant, because the chemicals wash away and break down over time.
But with microgreens, and especially sprouts, where you have so many seeds in one little area, you need the right seeds.
You want to make sure your seed provider is certified, and that the specific seeds you’re buying are fit for human consumption. If you’re eating a tomato from a plant that was planted 4 months ago you can get away with almost any seed, but if you’re eating sprouts, or growing microgreens, you’re too close to the seed to risk it.
Buying Vegetable seeds
A lot of them are 100 seeds per packet. Which is just too few seeds for microgreens, you need to buy by the ounce, or pound! In bulk! Not only does the price come down, but people who sell more seed, usually have fresher seed.
It’s easy for little 100 seed packages to get lost in the back of a store, or sitting in a box. Seeds that’s aren’t fresh, don’t germinate evenly and quickly enough to make good microgreens.
Order seeds from somewhere that moves a lot of seed!
Starting with difficult microgreens
Some microgreens are just harder to grow. Maybe you can’t find much information on them, or maybe there’s some trick you just can’t figure out.
Microgreens can be difficult to grow for a few different reasons:
- There isn’t much information available
- Inconsistent germination (many popular microgreen seeds are selected for even germination)
- The seeds are hard to source
- Small seeds (and thin stems!)
- Seed hulls that don’t shed
- Mucilaginous seeds (I can hear you asking what’s that? More info here) https://planthardware.com/what-are-mucilaginous-microgreens-brilliant-tips-for-successful-grows/
When you’re first starting out, stick to easier varieties, and spend a few minutes reading up on them. And make sure you follow all the right steps. Adding a bit of method to your madness and taking a systematic approach can really help your microgreens grow fast and strong.
How to Grow Microgreens in 11 Easy Steps (Updated 2020) (Links to Article)
If you’re up for the challenge, or want to get a feel for what to avoid at the start, check out this article:
Hardest Microgreens to Grow & Secrets of Success (Links to Article)
I’m Alex Lafreniere. I learned a lot about plants when I built and operated a landscaping company. I learned even more when I started growing and selling Microgreens. But, learning is a journey, not a goal. Ever since travelling across the world, I’ve wanted to find ways to bring more delicious and exotic plants into my life. This is the site where I share everything I’ve learned with you. And maybe we’ll learn a thing or two together.
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