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Your microgreens should have no issues if you are careful about hygiene and planting seeds correctly. But if something does happen, it’s likely to destroy your entire harvest. Even worse, some may spread to other trays of seeds.
That’s why it’s important to understand potential common microgreen problems and how to deal with them. Armed with this knowledge, you can tackle any issues as soon as they pop up, saving your harvest and making growing microgreens stress-free.
Mold
One of the most common microgreen problems in warmer climates is mold.
When surfaces are wet due to high humidity, the tiny spores invisible to the eye float through the air, land on a surface, and begin to grow. The network of mycelium then spreads out, covering seeds and seedlings with white, grey, or black fuzz and causing them to decay and die.
Mold often looks similar to root hairs, a natural occurrence allowing seedlings to improve water absorption. Mold will look like spider webs, creeping along the soil’s surface. If left, it will grow upwards over the seedlings and kill them off.
How to Fix
- Fix the humidity issue by increasing the air circulation around the plants. Fans are a good choice to keep the air moving. If you can, use a dehumidifier to reduce the moisture in the air and prevent the surface soil from staying wet.
- Some seeds are more prone to mold than others. In areas with high humidity, instead, grow seed that has some resistance to mold.
- When you cover your seeds, you may have to open the cover for a few hours to prevent the moisture from building up and mold from taking hold.
- Some seeds are mucilaginous (that gelatinous substance around a seed, like chia seed). In this case, spread them out carefully onto the substrate. Clumps will attract mold.
- The bigger the seed, the bigger the surface area, and the more likely they will develop mold.
- Make sure that trays are perfectly clean before sowing.
- To kill off mold, try a solution of grapefruit seed extract diluted with water.
Damping Off
Like mold, damping off is caused by different soil-borne fungi. It takes hold when seeds germinate and before they have formed their true leaves.
Usually, six to eight weeks is crucial to prevent the disease while the seeds are germinating. Cool, wet, and stagnant air are the keys that allow the fungus to attack and become a serious microgreen problem.
How to Fix
- Seeds that are slow to germinate have a window of opportunity for damping off to occur. Choose a seed that germinates quicker, and soak the seed before using it to speed up the process.
- Keep seedling trays warm (not hot) by placing them on heated seedling mats or increasing the temperature using an air conditioner or fan.
- Decrease the humidity levels with a dehumidifier.
- Never use garden soil to start seed, as this may contain soil-borne fungal spores just waiting for the right environment before activating. Instead use seed starting soil.
- Make sure the seedling starting mix has good drainage by adding extra materials like perlite and vermiculite.
- Add extra light if there is a chance of damping off. The sun’s heat will help ward off the disease but be careful not to burn the little plants.
- Avoid overcrowding seed in a tray.
Slow Germination
Some seeds are generally slower to germinate than others. For example, when it comes to chilies, the hotter the chili, the longer the seed will take to germinate.
Some seeds kept in the kitchen drawer for too long may not germinate at all, and some seeds also like a boost and soaking before sowing to get them going.
How to Fix
- Always buy fresh seeds for growing microgreens for the best results. Most seeds will start germinating within two to four days.
- Some seed packets will have a germinating rate on the packet. Don’t use any seed with a germination rate of less than 75%.
- Do a germination test if you are not sure. Dampen a paper towel and place about 20 seeds on the paper. Once they have sprouted, you can see which seeds have not germinated. If you only have 15 of the 20 seeds germinated, it’s at the base of 75%, which means these seeds should not be used for microgreens.
- Make sure your seed trays have enough water and increase the watering if the soil is too dry.
Bad Seed
Some seeds are simply not viable. In this case, the problem is not with care or environment, but what you’re planting. This microgreen problem is difficult to diagnose, but worth a try if you haven’t found any other culprits.
Try another supplier if you have very low germination rates or no germination at all.
How to Fix
- It is best to buy seed from a reputable seed supplier like Botanical Interests with a reputation for selling fresh seed.
- Look for seeds that are packed in hermetically sealed bags. This will give you a fresher seed.
- Seed suppliers will only pack onto the shelves a seed meant to be planted in that season. The seed has an expire by date, which can be from just a season to two or three years, depending on the variety. Most seed packets will show you a date indicating the best time to sow for the best germination rate. For microgreens, you want the best rate possible.
- If a deal is too good to be true, it probably is.
Incorrect Soaking Time
Some seeds are soaked before sowing to allow the new growth to push through the hard outer shell more easily than if they are not soaked.
This is particularly good for bigger seeds like beets and peas, but some seeds should not be soaked. These are usually the smaller types like radish, celery, and carrots. Generally, soak seeds for six to eight hours and no more.
How to Fix
- Don’t soak mucilaginous seeds like chia, arugula, basil, brown mustard, or cress; you will just have a gelatinous mess.
- Wet seeds can be difficult to handle and clump together if not sown correctly.
- If bigger seeds do not get enough soaking time, they may not germinate at all, or sprouting will be stunted and minimal.
- Don’t leave seeds soaking for long periods, or they may decay and rot.
Uneven Seeding
Uneven seeding can result in haphazard seed germination and uneven distribution. This is usually caused by not preparing the growing medium in the trays correctly. It can also be caused by using the incorrect rate of seed that should be sown per the tray size.
How to Fix
- When the growing material is placed in the tray, it needs to be leveled off and tamped down to provide a smooth surface. This should be done lightly so as not to compact the soil.
- Carefully calculate the amount of seed and measure it before sowing to get the best results. Adding more will be a waste.
Clumping Seed
This is another microgreen problem associated with sowing. Clumping creates crowded pockets of seed instead of a nice even sowing, impacting growth and harvesting.
How you sow and how you water will influence seed movement in the tray, and ultimately, how they germinate.
How to Fix
- Don’t soak seed that is too small. This makes it very difficult to sow.
- Water your growing medium before sowing so you don’t water your seed into a clump.
- Water using a rose-head nozzle on a watering can to water trays or a misting bottle. Start outside the tray area and move across in an even motion.
- If you need to water after the first sowing, water from the bottom to get the water to the surface so that the seeds are not disturbed.
- If you are having trouble getting an even seed distribution, add the seed to a kitchen sugar shaker and sow them evenly.
Yellow Seedlings
When you cover the trays to get them to germinate, they will naturally yellow because they need light to photosynthesize. However, if this continues after you lift the covers, you may have a problem with light.
How to Fix
- Lift the covers off the trays a bit earlier than usual.
- Give the seeds a stronger light source. A grow light or a little more sunlight daily will likely solve the problem.
Weak Seedlings
Most of the problems above will result in weak seedlings with poor growth. If you have discounted all the above, there are a few other solutions you can try.
How to Fix
- Increase the moisture content of the growing medium and mist more often.
- Decrease the amount of water if the seedlings are drowning.
- Prepare the seed correctly for its variety before sowing by soaking and not oversoaking.
- Prepare the trays with the growing medium correctly.
- Don’t take the blackout dome off too early. Be crop-specific in this regard.
- Read the seed packets and research before sowing a new type of microgreen.
- Make sure everything is clean. Clean trays thoroughly with warm, soapy water and sterilize if needed.
