*Experimental* Harvest 100's of Self Watering Microgreen Trays Under $60

Introduction: *Experimental* Harvest 100's of Self Watering Microgreen Trays Under $60

*UPDATE 1/1/20 - They're looking good. They're all in full light cycles excluding the control. But the control is starting to bloom. The icky trays are starting to get bigger too. I've also started some other trays with quarter paper towels. So fingers crossed. I'll update as I go. There's more recent photos I put up, they're the ones with the notes behind the trays. Happy New Year's!
*UPDATE 12/29/19 - The 5 additional trays are a bloom, excluding my control *ironically*. I left for vacation and didn't water it and it didn't germinate. But all the other ones have opened and are starting their journey. And the quarter paper towel got a little messed up and the seeds for shifted around. The original 3 are also sprung, but their fungal problems have gotten worse. Seeing similar fungus in my mycology projects, I think it's cobweb fungus. I'll post all the pictures of their progress with their annotations. The dates in the pictures are start dates and their method.

*UPDATE 12/27/19 - So after a couple days, germination only takes a couple days, I've come to realize the growing medium is to saturated. So I've started an additional 5 trays with different methods including; Quarter strip regular paper towel, thicker growing medium, paper towel with no medium, individual unfolded paper towel, and a control tray that I individually water daily as needed. I've come to notice with the first tray that the oversaturation is causing fungal issues, which could be stemming from my mycology project but most likely is just oversaturated. I'll update in a few days and try and include pictures. Also, the broccoli seeds came in, and to cover the tray, it takes 5g of seeds. Didn't measure in 1/4tsp but will try to remember to later. Thanks!

This is an open Instructable of how to make 100's of microgreen trays for under $60!

For those that don't know what microgreens are, microgreens defined by Wikipedia:
Microgreens are vegetable greens harvested just after the cotyledon leaves have developed. They are grown or purchased by people focused on nutrition, or else are used as both a visual and flavor component, primarily in fine dining restaurants.

With that being said. I call this open because it's an untested, and unconfirmed experiment that I believe has good potential and may spark similar, and improved designs for the future.

This design gives you 7-15 trays that can be reused with the 1lbs of seeds you purchase, and is an easy way to get started into microgreens. So make it your own, share your trials, and help improve it!

I'll do my best to update as the grow continues. Thanks for looking!


Supplies are as follows:

Freshware Meal Prep Containers [15 Pack] 1 Compartment - https://www.amazon.com/dp/B073TRVFZS/ref=cm_sw_r_sms_apa_i_b2OaEbP9PHB0K

(Optional, this will give you quicker and better results)
General Hydroponics FloraGro 1 Quart https://www.amazon.com/dp/B000BT3UAM/ref=cm_sw_r_sms_apa_i_H3OaEbP8W3ZGK

Everwilde Farms - 1 Lb Green Sprouting Calabrese Broccoli Seeds - Gold Vault https://www.amazon.com/dp/B00HMFR10I/ref=cm_sw_r_sms_apa_i_A4OaEbP2402ZC

Coco Bliss Premium Coconut Coir Pith Block 10 lbs https://www.amazon.com/dp/B06W9F7XDY/ref=cm_sw_r_sms_apa_i_Q5OaEbSA9SC62

Paper Towel


Screwdriver or small metal bar


1 cup measuring cup

(Optional) Blender

Step 1: Creating Your Tray

The first step to this design is the construction of the tray. I got the idea from Mike Vanduzee and his video:

The experimental portion of this involves finding the right growth medium and material to wick water. I chose to go with coco coir and paper towels since I had the coir lying around and almost everyone has paper towels.

I had 3 different kinds of paper towels lying around including a quilted pattern shop paper towel, a non-quilted shop paper towel, and regular paper towels. So I chose to do this with all 3 and see how the absorbsion qualities affect the growth.

To begin the construction, you'll want to do this portion in a well ventilated area. After the first tray, I moved to the stove hood because smoke was a little nauseating.

Begin by taking one tray and one lid out from the package and nest them on top of each other. The slit you will be creating can be made the same size as your paper towel folded in half shortways (think hotdog, not hamburger).

Start heating up your screwdriver/metal object, make sure it isn't more than a quarter inch in diameter. I heated it until it began to glow a faint red in color using a butane torch. You can alternatively use a lighter or candle in place of this.


When it is nice and hot, place it on top of the lid at the edge right where the curve meets the straight part. The screwdriver will quickly melt into the lid, make sure not to go to deep or to close to the edge of the container and begin to pull it 90° towards the edge on the opposing side. Depending on how hot the screwdriver is, you may need to reheat it part way through. I found I could do one half a lid before reheating.

Reheat and do the same on the opposite side of the lid. Make sure the line is melted wide enough to fit your paper towel in, but not to large that your growth medium will fall into.

Now flid you lid upside down so it sits inside your container. Take your paper towel and slide them into each slot you just created. Make sure it's evenly inserter on both sides then fold the underside in towards the middle.

You now have the main portion of the tray created. Next is filling the tray with your nutrient water and adding your growth medium.

Step 2: Adding Your Water and Nutrient Solution

Now that your tray is created, next we will be adding water, and the optional nutrients.

Remove the lid we just created and add 2 cups of water to your tray. This will come up to about half an inch below the bottom line of this particular container.

Next we will add our nutrients. This is an optional step and will save you about $15 off the total price. But excluding this step will potentially result in longer grow times and shorter overall growth.

Based on our bottles calculations of 1/4tsp of nutrients per gallon of water for seedlings. The calculations break down like this (if my maths wrong, CORRECT ME):

We need 1/8th of this ratio- 1/4tsp = 1gal
(1/8 of our gallon of water, 1/8 of our 1/4 tsp)

Some conversions include-
1 gal of water =16 cups.
1 cup is 237ml
1/4tsp =1.23ml
1tsp = 4.929ml
1 drop of water = 0.05ml

So, taking an eight of our ratios we get-
2 cup of water (474ml)
1/4 x 1/8 = 1/32tsp
(1/32) 0.03125 x (1 tsp in ml) 4.929 = 0.154ml

Which makes our ratio-
0.154ml per 2 cups of water
Simplified - About 3 drops (0.05ml/drop) of nutrient solution per 2 cups of water

That takes care of the water and nutrient side. Next we'll move on to the growth medium.

Step 3: Plant Growth Medium

In this step, we will be adding our growth medium to the top of the tray, this will be done prior to setting your lid over the water.

To begin, I find this step is best accomplished by using a blender. It's not 100% necessary, but I find it shreds the coir into finer material and takes alot of hastle out of breaking it up. Otherwise, skip the blender and instead use your hands.

Start by opening your bag of coir and break off chunks to fill your blender. You'll find a more complete and quicker blend when using small amounts at a time.

*These measurements will be talking about dry coir material.*
Coir is an amazing, non-nutritive material that can absorb up to 9x it's weight in water. I found that each tray takes around 100ml (1/2 cup) of dry coir to fill. So I did 300ml to fit all three. Make sure that any big chunks are broken apart. You can see in the picture above that there's chunks in it that will make it hard to level off later.

It's easier to do 100ml at a time and fill one tray vs do all 3 at once. If your breaking this up by hand, it might be easiest to break it down to 1/2" or 1" size and estimate 100ml. Then add a little water to break up the hard pieces. It expands and falls apart when wet. If you go this route, make sure you squeeze the majority of water out before adding it to the tray.

Fill the coir so it is almost level to the lip of the lid. Then set your lid over your water, ensuring the flaps on the underside are tucked in towards the middle. Almost immediately the paper towels will begin wicking up and start being absorbed by the coir. You'll notice the coir will expand and dampen rather quick.

Once you see the coir is evenly wet, take one of your spare lids and slide it under the end of your tray like in the picture above. Then take another lid or anything straight that can be slightly wet, and skim the across the top of your tray.

Make sure to fill in any holes and break up any clumps you may have. Once it's all filled, skim it onto the tray underneath and catch it to avoid making a mess.

Do this with all of your trays and create a nice even, level surface. This is important for your plants. The last two pictures show the leveling and excess coir from all three trays combined.

In the next step I will show the different paper towels I used and their water absorbsion for informational purposes. If your not interested, this step can be skipped and you can go to the last step for seeding instruction.


This is where I'm looking for community involvement. In this step, I used the 3 different paper towels to see the difference in absorbsion and saturation of the growth medium.

All 3 took only about a minute to completely saturate the paper towels. You can see the difference in the two shop towels in these pictures. Each photo is about 15-25 seconds apart.

The images of the coir becoming saturated took about 2 minutes, excluding the regular paper towel. This took about 3-5.

Some of my worries are over absorbsion with the shop towels, which started to become more apparent after several minutes. This could be bad for some plants and prohibit growth.

The other worry is the longevity of these, I don't exactly know how long they'll stay together being saturated 100% of the time.

Something I'll try next time is tearing them in half so it's not folded or separating the plys (some of them are two plys stuck together).

Step 5: Seeding and Supplemental Info

In this final step and I will go over how I seeded and left them to grow.

For these trays, I wanted to grow dandelions (since they're edible and I had seeds lying around).

I began by weighing out seeds that I thought would be enough to completely cover the tray. I put them in a spare lid and weighed out 2.5 grams. After sprinkling them evenly, I reweighed the leftovers and found a around 1.2 grams left which meant I used around 1.3g.

Knowing not everyone had a scale to check these, I wanted to use a common measurement. So I used a 1/4tsp measurement and checked what a leveled off 1/4 of seeds weighed. To my amazement it was around 0.6 grams! So it easily worked out to about 1/2tsp per tray.

For the last part, I lightly misted the new seeds and took some left over trays and put them upside down on top. (So it'll be tray, lid, tray) This will stay on top for 1-4 days, depending on species, to make the crop elongate and reach for the light. Then after the dark period, you'll take the top tray off and expose to light.

I stacked the trays to show you could save space. With this method, you can make 7 trays at a time (if you use tray, lid, tray) otherwise you can make 15 trays at a time and use something else for the blackout period.

Depending on species, it'll take anywhere between 7-16 days to grow a harvestable tray. Broccoli Avg. days to maturity is 12.5 days when harvested at the first true leaf (as opposed to cotyledon). When it hits harvest time, use a sharp knife of scissors and cut about 1/2" above the growing medium, wash then serve. You can periodically harvest as needed. Just don't wait to long. Do some research on good seeds and easy grows to start with and enjoy healthy fresh veggies for you and your family.

I made this Instructable based around using dandelion seeds, but used broccoli seeds in my supplies list. I checked some numbers and found these numbers online:

1700 seeds per gram dandelion
2550 per 1.5 gram

285 seeds per gram broccoli
427 per 1.5 gram

Now, I didn't do the math exactly because I don't know the size of broccoli seeds since they haven't arrived yet. But even if you use 4 times the amount of broccoli seeds (~1708 seeds) and since there's 454 grams in a lbs. You'll still get 75 trays of broccoli.

I hope this will inspire some similar grows and I will update as it goes along, hopefully with good results!

Thanks for reading and happy holidays to you all!

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    1 year ago

    So you had a problem with fungus growing in the paper towels as well? I had that happen to me. My own project- or rather FAILURES- are posted here, and shows how hard it is to create a project like this.


    Reply 1 year ago

    Unfortunately, it was a problem for a little bit. But a fan and smaller paper towel took care of it. The issue was they were allowing to much moisture to wick up and would oversaturated the coir. But Ive harvested 6 full trays now and just made an additional 11 yesterday. I'll probably end up remaking this Instructable and dropping a link on this here to it.