Automated Microgreen Bottom Watering System – DIY

We finally made the investment in automating our microgreen growing set up and it has demonstrated immediate time savings of several hours a week (and we’re a small scale grower).

Prior to building this system we had all of our germinated 1020 shallow trays with their own white, leak-proof bottom watering tray. This, not surprisingly, requires a human to lift up each micro tray, and fill up the bottom watering tray with a hose – sometimes up to 3 times a day when it was hot! Talk about a giant time-waster!

The reason we went with bottom watering in the first place is due to the improved growth that resulted from not wetting the young foliage. When we started out and were still top watering invariably we’d get foliage sticking together, then humidity increases, then airflow gets restricted and viola, mold growth! The bottom watering solved the mold problem by and large, along with some fans to help improve airflow. It also served to better buffer the moisture availability to the young seedlings so we had less losses from wilt (though we still had some, because you can’t watch it every hour of every day).

This system does away with the individual white, leak-proof bottom watering trays, and instead we put (4) 1020 shallow germination trays into a sump tray. This helps us limit the number of “fill up” points in the system.

All of these sump trays sit on a level platform so that any water in the bottom will be evenly distributed throughout the tray.

Next each tray gets (2) 45″ long pieces of 1/2″ Schedule 20 PVC pipe. These pipe segments act as a spacer to help support the 1020 trays and to keep them from collapsing (they get rather heavy when the soil is saturated, and their lips just barely reach across the sump tray – not enough to make it secure). These pipes also ensure ample volume underneath the 1020 trays for water and/or wicking medium.

We then filled each tray with about 1/4″ of sand, so that just in case our platform ever deviated from level (known to happen when our clay soils get wet) they could still carry and retain moisture throughout the bottom of the sump tray.

For the water inlet we used 180 Shrubblers – which allow you to regulate the flow rate at the emitter head by simply twisting it. We also drilled two outlet holes just slightly lower than the inlet to make sure the water level in the trays would self-regulate (i.e. not swamp our delicate micros). We drilled these outlets just below the top of the PVC pipes so that there would always be a little bit of air between the 1020 trays and the water.

Each tray also has a 1/4″ inline valve that allows us to shut off the water supply to any individual sump tray when it is not in use.

The entire rack is run off of a single 3/4″ solanoid valve that is controlled by the Galcon AC 6S Irrigation Timer (this timer allows for cyclical irrigation patterns as well as intervals as small as 5 seconds). We currently have it run for 4 minutes 3 times a day and that keeps all of the sumps topped up nicely with minimal overflow.

Here’s a quick video tour of the system so you can see how the components connect and how it operates.

Any questions about the DIY process please drop them below!

2 thoughts on “Automated Microgreen Bottom Watering System – DIY”

  1. Casey,
    Very interesting setup. I’ve only dabbled in micro but have seen that bottom watering appears to be far better than top. Congrats on figuring out cilantro. I’ve gathered that it’s tricky. I’m in north central Texas. This summer we dipped our toe in the beginning farming and farmers market game. It’s a meager start as markets are not strong here. Plus my current model stinks.

    Couple or so questions if you don’t mind:
    1. If you have air between the bottom of the growing trays and the drain holes how do you get water to the soil?
    2. Doesn’t your bottom layer of plants get a far different amount of light? I’m not sure about trying this in an insulated barn or a caterpillar tunnel with additional lighting.
    3. The first time I tried micro it was in high texas heat vs the ‘recommended’ lower temps. Their taste was not good, awful in fact. Shortly thereafter I attended a ‘the survival podcast’ workshop grown indoors in 75F and I got it! They tasted great! Sine you appear to be in high heat how does that affect your growing?
    4. Since marketing is a big part of the game how marketable is the cilantro? Bunches are very available at a low price here.


    1. Hi Steve,

      Thank you for checking out my video. I hope your future farming endeavors go well and things pick up for you!

      Here are my answers to your questions.

      1. The system is designed to have about 1/8″ air pocket between max water height and the tray bottoms – that being said, we are on uneven ground and trays sag etc – so many of the tray bottoms do actually touch the water surface.
      2. Yes, the rearmost trays on the bottom do get shade – for us this is OK because shade is a scarce commodity here during summer. Our pea shoots do very well with just the reflected light.
      3. High heat has been a huge issue to contend with. One of the primary drivers behind building this unit was to get our micros OUT of the greenhouse in summer. Cilantro is super finicky in the heat, very easy to lose entire batches prior to germination is the tray temp gets higher than 78 or so for any extended period of time – this meant keeping them under tables, multiple waterings per day etc. Outside with shadecloth for us is the sweet spot, but our ambient temps aren’t that high (we’re 3 linear miles from the coast). In Texas I’m sure its a wholly different ball game than here.
      4. Interestingly enough, the market demand is the only reason I hung on this long and figured cilantro out – our chefs love the micro cilantro. It is very different in texture and more subtle in taste than full grown cilantro you’d find in bunches. The chefs also really like the appearance as a finishing element on their dishes.

      That’s awesome you’re a TSP’er! I’ve been listening for 6 or 7 years now, have always wanted to make it to a workshop at Jack’s place since he started holding them.

      – Casey

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