How to Grow Microgreens using Sprouting Trays:
If you’ve watched our YouTube channel before, you may have seen us using some trays that are smaller than the typical 1020 trays used for growing microgreens. So, what are these? Technically, they are called “sprouting trays” and aren’t actually meant for growing Microgreens, instead their meant to be used for “sprouting”. Since sprouting is a completely different method of growing, they do have some growing challenges to overcome in order to use these “sprouting trays” as microgreen grow trays!
Now that you know there are some “growing challenges”, you may be asking yourself – “okay? Then why not just use regular microgreen flats then?” … The biggest benefit is the cost.
These Sprouting trays are fantastic when it comes to cost savings if you want to grow more greens and not spend a ton of cash on trays right away… that and since they are smaller it saves you some space. But don’t be fooled by the trays size… what we’ve learned is that we can still get high harvest weights using these sprouting trays to grow Microgreens, despite their smaller size. The benefits of these smaller trays outweigh the challenges in our opinion.
To get started, choose your grow medium. We suggest using a seed starting soil, coco coir, or a reusable mesh with these trays. After you have selected your grow medium, place the white mesh tray so that it’s sitting in / on top of the solid green tray (just like we do with 1020 trays). If using a soil or soil like medium - fill the white mesh tray up with the grow medium until it's about ¾ full. We typically use 3 cups of soil or coco coir per sprouting tray. But if you’re using a reusable grow medium (like ours), simply place it onto the white tray and move into the seeding steps.
Once the medium is in the tray, break apart any clumps that you may find, and if you’re using soil that has twigs in it, remove any of the larger twigs (Microgreens don’t like growing on sticks). After removing clumps and the larger twigs, take your hands and distribute the grow medium evenly across the tray. Once even, lightly tamp the soil by gently pressing down on it (do not compact it).
Then, using a scale with a cup on it, measure out the amount of seed needed. We suggest about 1-3 tablespoons per tray depending on what seed you use.
If you’re unsure of how much seed to use, you can take a look at our Free Downloadable Microgreen grow guide on our website underneath the “resources” tab. For the sprouting trays, you’ll take whatever the amount is on that guide (which is the seed amount for a 10x20 tray) and divide it in half to find the amount needed for these sprouting trays. This way, you don’t over seed since these sprouting trays are smaller than the 10x20 trays.
Once you have your seed measured, using your hands or a seed shaker, evenly distribute all of the seed across the grow medium, making sure not to group all the seeds together densely.
After seeding, use a spray bottle (we suggest these types) to generously water the seeds and grow medium until wet, but not over-watered! Too much water can cause a lot of issues such as mold, damping off, and slow growth.
Once you have watered your seedlings, remove the green tray from underneath the mesh tray, knock out any grow medium that fell into this tray into your compost, and then place the green tray on top of the seeds so that the tray sits on the seeds.
At this point, you can add some weight to the top, such as a 5lb to 7lb brick on top of the green tray, OR you’ll leave the tray without the added weight, and the tray itself will act as the “added weight.” The weight needed varies per crop variety, and again we have this information listed on our grow guide for easy understanding along with our suggested amount of time you should use the W= Weight or ET = Empty Tray. The weight can be very beneficial when it comes to even seed germination & seed hull removal – (check out this video we did on this topic!!)
After adding the brick on top, place your tray onto a dark shelf where it can begin to germinate. Check and water your crop generously twice a day, every day, morning, and evening. Give it more or less water, as needed. The goal is to keep the soil moist which helps the seeds to expand and burst out of the shells. About 2 to 4 days later (for most crops), your microgreen seeds will be germinated and should be starting to push the tray / weight up themselves. At this point, you should no longer see many seed hulls; instead, it will look more yellow from the plant leaves showing through, rather than the dark seed coatings. Once you confirm that your crop is ready, remove the weight.
After removing the weight and tray, mist your microgreens as usual, then take the green tray, flip it over to create a dome, and place it on top of your mesh tray for Black-Out. You’ll then place your tray onto a dark (no light) shelf for 1 to 2 days (depending on the crop) and you no longer need the weight.
The reason we put our crops into “blackout” is so that they can stand up taller and begin growing longer stems (makes for easier harvesting later).
Tip: Beware not to leave them in blackout for too long or you’ll have a lanky crop, which topple over and they won’t be appealing to the eye. The goal is to only slightly stretch the stems for easier microgreen harvesting.
Once the crop is ready to come out of blackout, take the green tray and place it back underneath the mesh tray so that it acts as a reservoir and then introduce your microgreens to the light for the very first time where they can start to green up. This is also when we began bottom-watering for the first time and/or introducing hydroponic nutrients.
If you used a grow medium such as soil, do not add any nutrients hydroponically, you’ll want to bottom water with regular water, or you could stunt the growth and/or cause tip burn! But, if you used coco coir or a reusable mesh, you could boost your growth of your microgreens by bottom watering with hydroponic nutrients (optional)! To do this we use a 3-gallon food-safe bucket, and mix our nutrients of choice, then PH-balance our water after mixing in the nutrients. For instance, if we’re using OceanSolution™ 2-0-3, we will mix it at the ratio of 0.5oz. per gallon of water, then PH-balance the water to the 5.5-6.0 range for microgreens.
Alright, well remember how we said that these sprouting trays become tricky vs. using the 10x20 trays… this is when you can run into a learning curve. Since the mesh tray and the green trays sometimes have a void in between them (the void size varies depending on the brand), you have to fill it up with a decent amount of water; generally, about 2 to 2 ½ cups on the first day of watering your microgreens, compared to 10x20 trays where we usually start them with about ¼ cup of water then bump it up to 2 cups as they need it.
When filling the green tray up with your bottom-water, make sure you fill it until your mesh tray slightly touches the water! You can determine this by filling it some, then allowing the white mesh tray to sit normally for a moment, then slightly invert the mesh tray to check for any water droplets. If you don’t see any, it needs more water. But if you do see water droplets or the water moving from the tray being lifted, you should be filled up enough.
Remember to really pay attention and make sure that you DO NOT overfill the tray with water. It shouldn’t have puddles of water forming where the seeds are; just enough to wick the water up to the crop.
You’ll check your crops and bottom-water levels twice a day. You want to make sure that the medium is not very saturated. If the grow medium becomes very saturated, skip one watering for the day to allow it to dry out in-between watering’s. But if you notice that the medium is dry and / or crops are looking sad and are beginning to wilt or fall over, add a little more water as they may not be receiving enough.
Watering is really the key to success when it comes to using these sprouting trays to grow microgreens – It’s good to keep in mind that with these trays, you’ll need to check every 2 to 3 days to see if you have water sitting in the green tray from previous watering’s. If you over-water, you can pour out the old water and refill it with new water. This way, you don’t get stagnant water, which can become smelly and invite disease.
Once you overcome the watering difficulties (if you have any), in 7 to 14 days (for most crops) it will be time to harvest your microgreens and you’ll be able to apply any learning's you had while using these trays to successfully use them to grow microgreens every single time with ease!! Now that we have used them often, we never run into issues anymore and they have become a favorite tray to use.
Tip – If you’re curious about learning more on how to grow microgreens and/or want to know more about the other types of trays, be sure to check out our book “Becoming a Microgreen Master” – it has a great section that goes more into depth on buying the right trays plus tons of great tips to get you growing like a pro right away!
We hope that you’ve enjoyed this blog on How to Grow Microgreens with a Sprouting Tray and we wish you the best success in all your grows!!
Reference: Growing Microgreens in a Sprouting Tray
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Written by: Mandi Warbington
Edited by: CJ Vaughn
Published: October 29, 2021
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