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Microgreen Germination and Seeds FAQ

September 17, 2021 4 min read 0 Comments

Microgreens grown with lights


From our How to Grow Microgreens Series

Transcript below has been edited for clarity.

Nick & Nathan from On the Acre in Houston, TX discuss germinating microgreen trays, stacking trays, blackout domes.



So whenever we're germinating microgreens, we end up stacking them after they're planted all on these racks. The bottom shelf is typically used for the stacked whereas the top two shelves are for our domes. You'll see that we have a variety of different tray sizes represented, as well as these bricks on top {acting as weights on top of stacked trays}. A really cheap solution is to go buy some jars and fill them with sand and it works really well to distribute weight around and it doesn't cost very much money. Bricks don't cost much money either but they are, very much you know, one particular shape. These {jars of sand} fit in 5x5s, these {bricks} fit larger {trays}. Yes, that's a great distinction.

So what's happening here is the seeds have been distributed evenly across the surface of the trays. The top of the soil has been moistened very well. These seeds just sit here and they soak. Eventually they start to sprout and in about four days they're ready to unstack {and put under domes}.  In about a week they're ready to be moved from the domes into the light. The lighting that they get in here is fluorescent lighting. We have our office in here also so it's dark at night, light during the days while we're in here. There's no special thing that happens lighting wise for them. Like we've talked about before they are in the dark because they're stacked under one another, minus the {trays that are under} domes.

As we move into the colder months right now; we've just recently brought out our heater because germination slows whenever it's cold. The colder it gets the slower the germination takes place. We need germination to occur at a constant pace. That way we know when our plants are going to be ready and in order to do that we try to maintain a temperature of around 65℉ to 73℉ in here. Because that's what we keep it up during the summer when it's warm so as long as we maintain the same conditions year-round then the plants will react the same way.

We talked a little bit about light and humidity is another factor you need to take into account. so one of these simple little magnetic thermometers. We have them in each room to tell us the temperature and humidity in the room. Hydrometer is the word that you look for when looking for a humidity reader.

If humidity gets too high we use a dehumidifier in our grow room. Depending on what {the humidity is} outside you could open a window if you wanted to but then you're letting in things from outside, allergens, pollen, things like that. So we have a dehumidifier for that case. {The hydrometer is} also nice since it tells you average highs and lows for a day. It lets us know, while we are not there, if there are temperature changes going on so that we can be more aware of that overall.

You can see that the range in here is from 59% to 46% humidity and 74℉ to 68 ℉. We're trying to keep humidity below 70%. If you get up into the 80s, {that} is where you really start to see problems with mold and fungus, etc. So we give ourselves that 10% buffer zone to keep it safe. So if it does get up at 75%, you know occasionally, it's okay. But, you really want to stay below 80% because that's when it starts to get icky.

When talking about microgreen germination we went ahead and brought down three of our trays for you, we removed the domes from them so you can see what stage they're at. This right here is amaranth and it's ready to be moved into the light. You can tell that because of how tall the amaranth plants have actually grown. There's going to be some close-ups of the amaranth so you can actually take a look at the roots and how they grow and how the plant comes up.

The next tray you're looking at is lemon basil and it is just the right time for it to go over. It has about a finger length stem, so maybe about an inch stem on it. {You} might not be able to see here but there's a little bit of a directional like movement to both here {lemon basil tray} and here {amaranth tray}. That's because, like I told you, our light source is here and our germination {rack} is against the wall. So they pull a little bit towards the light as they germinate and then they fix as soon as you get them into the grow room when the light is directly above them.

That is called etiolation, whenever a plant reaches for the light. That is what {you see} when you use a blackout dome. That is the reason that they stretch, that the stems stretch, because the plant is using all of the energy located in the seed to grow {towards the light}. The stem thinks it's going through soil because there's no light yet. As soon as the light hits the leaves the cotyledons start producing energy for the plant to continue growing. So that is why they lean towards the light because they're not getting quite enough yet.

The tray on the end is our mirepoix farms. We have three different varieties in these. The closest one to us is carrots, then you have bunching onions, and on this side you have celery. So they all were planted at the same time and are in a different stage of their germination. The celery, there are no visible stems coming up yet. And then our carrot and onion are both at about like a half an inch to three-quarters {of an inch} off the soil. We would leave these over here, for probably, at least another couple days before we transfer them to our grow room and put them under the lights. 

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