Hydroponic Grow Mediums for Growing Microgreens
Updated: Jan 3
In the world of Hydroponic Microgreen growing there are a ton of choices whenever it comes to grow mediums. From various products that have a feel similar to soil but without the same benefit of nutrients you get from soil, to Grow Mats that have been woven from different sources such as Coco Fibers, Hemp, Jute and so on. There are even options out there that can be reused!
You may be asking yourself, what is hydroponics and why use it to grow microgreens? Hydroponics is using water to grow plants without using soil. It is one of many "aquaculture" practices around using water to grow plants in non-traditional ways. The reason we love hydroponics is that it can be so much fun! You can mix and match grow mediums and nutrients to create the perfect microgreen growing recipe for you or your business!
To grow microgreens hydroponically, it is easiest to use a "growing medium" in place of a soil. This medium will act as something for the root and root hairs to grab onto so that the plant can stand itself up and grow well. Some crops like Pea Microgreens can be grown directly on mesh trays because they are very strong growers and will root into basically anything with ease. Generally, most microgreens grow a lot faster and stronger if they have a good growing medium. The goal is something that helps with germination through water retention and provides a good surface to root into.
For the past year we have accumulated a ton of experience around Grow Mediums after doing so many experiments on our YouTube channel where we are constantly testing them with various microgreen crops. Now we want to share with you some of the insights we have for each grow medium in the hopes that it will help you better choose the right Grow Medium for you and your growing needs!
First will start with the most challenging Grow Mediums and work all the way up to our favorite's!
Jute is a long, soft, shiny Bast fiber that can be spun into coarse, strong threads and it is produced primarily from plants. One of the benefits of Jute is it is a very sustainable medium, which there are many different brands out there who make Grow Mats using Jute for Microgreens. Just be sure that they are not using any fillers or binders in their product. The main challenge we've encountered with Jute is that we cannot get consistent and even germination. There is usually some part of the jute grow medium that doesn't germinate as well as the other areas. We aren't exactly sure why this happens on Jute, but we think it may be caused by inconsistent water retention throughout the medium.
10. Coco Mats:
Coco grow mats are made from thickly woven Coconut Fibers to create a hydroponic grow medium. What we love about this type of grow medium is that it is a sustainably harvested material, and the grow mats come fitted perfectly to our Bootstrap Farmer 1020 trays. This is one of those mediums where it does alright, but you just wish it did better. We have found that it does not retain water well enough during the initial germinating stage, which means that we must pay more attention during this stage of growth. We feel that this type of medium would do better in an actual hydroponic system, like an Ebb and Flow or NFT system. This is a medium that will have to do some more tests with and see what happens...
We put these two together because essentially, they are the exact same product… the only difference is the Mats version is a grow mat product and the Confetti is a shredded up version of the mat that they slapped a $0.40 higher cost per tray to. Both these mediums are made from Sustainably harvested Wood Fibers and come in a dehydrated state. The Micro Mats version of the product can be difficult at first until you learn how to place the mat in your tray. Sounds simple, but even though the sheets come fitted for a 1020 tray, once you add water to the product the mat ripples while also becoming soggy. If the mat is placed incorrectly, you have to be ultra-careful when touching the mat because it tears really easily once wet. We've noticed that this medium is quite dense, even when wet and sometimes crops struggle to get their roots through. We have had some crops turn out wonderfully…
As for the confetti, the main things we dislike is it costs more, and it makes clouds of dust from all the shredded material which gets everywhere... But the Micro Mats Confetti does seem to allow the roots and radicals to get through better then with the mat version.
8. Peat Moss:
If you're looking for a medium that is sustainable, peat moss might not be the best choice for you. Peat Moss is made from dead fibrous material that forms when mosses and other living material decompose in peat and it takes several millennia for peat moss to form. However, this is a solid grow medium and one of the benefits of Peat Moss is it a naturally sterile medium. Usually you will see peat moss mixed into soil to help in water retention and allowing better drainage since most soils can be full of clay. This is a medium that we have heard a lot of people using and they have had great results with it... but we're still experimenting with ourselves.
This is a medium that is like Perlite. Vermiculite is a Naturally occurring hydrated magnesium iron aluminum silicate mineral, that gets heated up in a furnace, then it expands and takes on a concertina shape. Usually people mix this into soils to help with drainage and rooting… but you can also use it by itself like you would use perlite in a Dutch Bucket System. Vermiculite also falls in the reusable category since you can wash and sterilize it, but it can be a process and may not be worth doing for most people. Of course, our experience with Vermiculite as a microgreen medium has not been tested just yet. So we don’t have a whole lot to say about this medium from our own experiences, but like Peat Moss we have had people recommend it to us to try…and if it works how perlite worked for us, it may be worth trying.
6. Paper Towels:
Good ’ole store bought paper towels have been a grow medium that has started growing on us. The main perks of paper towels as a grow medium are, they are cheap, and you can get them just about anywhere. But they do have a few downsides… First, they are prone to drying out depending on their water retention (varies by brand), plus you’ll have to be careful to avoid over-watering or you’ll run into a very foul smell caused by stagnant water.
What we have also noticed is the brand of paper towel will have different effects on your growth since some brands have 1 ply and others have 2 ply, each brand is also woven differently and made from different stuff. Which speaking of, you need to be careful when choosing paper towels for the use of growing since they may have been processed with bleach or other chemicals to make them white, and if they’re recycled paper towels you can still run into issues since you don’t know what the recycled material was used for to make the paper towels… which means they may not be food safe for growing food!
Lastly, we noticed some crops have a hard time getting through the medium and others do not during germination... We think the rooting issue can be overcome by adding more weight during germination. This has been one of those mediums that has a ton of potential! We suggest trying Paper Towels out if you are a home grower, and our tip would be going with a 2 ply paper towel and double layer it in your tray!
If you aren't sure what Perlite is, you've probably seen it and not known... Most potting soil mixes will have Perlite added into it to help with drainage and aeration. Perlite looks like small white rocks, but it is an amorphous volcanic glass that occurs naturally and has the unusual property of greatly expanding when heated sufficiently.
Most people in hydroponics like to use Perlite in Dutch Bucket Systems for the use of growing tomatoes since it holds on to water for the roots but also gives something to grab onto. One downside to Perlite is it is very dusty, and you will need to be careful when handling it… best thing we've found to do is lightly wet it first to help the eliminate dust. It is easy to spread in a tray which is nice, and it does hold onto water surprisingly well. Something that we learned when we used Perlite to grow Radish Microgreens is it’s best to use a mesh tray rather than a slotted tray if your using Perlite as the grow medium because the mesh tray allows the roots to really wrap around it making it way easier to harvest from this medium. We would not suggest using a slotted tray if your using Perlite as a medium. Another cool thing is you can reuse and wash Perlite, but it is a process that we have not tried yet. The only big downside to us with this medium is how messy it is, and that it may not work well for very small seed crops like Red Garnet Amaranth.
Every time we have used Hemp grow mats for experiments, they generally came in 2nd to 3rd place which is why it is on our top 3. So, what are Hemp grow mats? Hemp mediums are just loosely woven hemp fibers and this type of medium is great at retaining water to the point that you need to be careful not to over-water or you can run into germination issues and mold.
You should probably do a little research as there are many brands of Hemp grow mats and each can give different results... Terrafibre has been our go to currently for Hemp mats until we find something better. Most all our crops have done well on this medium, and we have only run into a few minor issues that were usually our fault because we gave too heavy of a watering. Once you get the hang of it, this is a great hydroponic medium to grow microgreens with.
Some of you may be thinking what the heck is Biostrate? Don’t worry, we thought the exact same thing originally… the answer is: it is a blend of biopolymers and natural fibers that is designed to manage water efficiently for optimal growth in a variety of hydroponic systems. This is a grow mat that we highly suggest because literally every experiment we did with grow mats, Biostrate came out on top with the best Germination, Growth and Harvest Weight. We hardly ever ran into issues with Biostrate, and if we did it was likely our fault because of us over-watering.
Now, this is not the medium for you if you're looking for something Sustainable. Hemp would be a better choice, and the other downside is it is not compostable in a home setting. If you want to compost it, you have to take to an Industrial Facility for it to be broken-down properly… which for us, even though it was amazing at growing… that was a major turn-off.
Tip- Biostrate & Hemp both come in big Rolls that you can cut yourself, we found that using a Paper Cutter like this (click here) is a extremely easy and quick way to cut the medium to size, rather then using scissors. Links ➟ (Biostrate Roll) ︱ (Hemp Roll)
UPDATED 11/5/21 - In the past we said that we loved the idea of Mesh Screens because and that the reason why it was at the bottom of our list was simply because we had not had any major success with it yet. But now that it's been basically a year since writing this original blog - we have done what we do best, which is testing and have since found a new love for mesh screens. In fact, we enjoy them so much that we now sell our own "Reusable Microgreen Grow Medium" and have an entire blog dedicated to them (click here to read it).
The benefit of mesh microgreen Grow mediums is that it's a medium that you can clean and reuse for a very long time. This is very attractive as a grower, because you can save money on your grow medium in the long run.
This is 100% our favorite Hydroponic medium and what we suggest everyone to use! Lets start with what Coco-Coir is… Coco-coir is a Hydroponic medium that has a soil like texture and is made from ground up coconut husks.
Coco Coir is low in most nutrients aside from Potassium and Sodium. Usually Coco-Coir comes in a super compressed 10lb brick that you add water to, which causes the Coco to expand and turn into a lot of grow medium. Coco-coir quality can really vary depending on where you source it from, so be sure to find a good brand. Also, some coco coir needs to be rinsed thoroughly because of its salt content (called buffering). We've found that most Coco Coir sources are fine to use without buffering.
What we love about this medium is the amount of control we have because we can either add our own Hydroponic Nutrients via Bottom Watering to boost the Growth of our Microgreens… or we can use plain H2O to Bottom Water and we still get really great results. Everything germinates amazing with this medium and grows perfectly. One down-side is that once it is re-hydrated and expanded, it takes up a lot of space. We just keep ours in a big open top tub that fits onto one of our racks… that way it has airflow and a surface above it to block stuff from falling into it.
That sums up our thoughts and experience on some of the hydroponic medium choices out there, but this list can change at any given moment since we're always re-trying mediums out and putting them in different scenarios. Keep in mind that our grow space is unique in its climate and may vary greatly from yours, which is why we always suggest the best thing to do is do your own research and experiments! If you're interested, check out our Grow Medium Experiments on our YouTube Channel to help you get a better idea of what we've experienced with each medium!
Want to learn EVERYTHING we learned from all our years of growing and experimenting with microgreens? Or maybe even learn some new recipes to use your Microgreens in?? Then check out our Books below!
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Written by: Mandi Warbington
Published: July 27, 2020
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