Are you wondering, why are we putting so much intention on different growing mediums? Well, this is because your decision on this will determine how your microgreens will look like and the process of growing it. They do require different growing technique or procedure, better to say. Let us first focus on medium types and then talk a little bit more about watering.
List of different growing mediums
Let’s talk a little bit more about different growing mediums. When you are not using soil, then the growing process is called hydroponic. But here we will focus on hydro systems that do require some substrate. Firstly let me expose some non-natural or better to say non-home compostable growing mediums.
Rockwool as a growing media is a pad made out of natural mineral fibers, produced from melted igneous rocks (no added chemicals). It is suitable for growing microgreens as it is very easy to use, hygienic and it has 95% ability of moisture retention, which provides ideal conditions for the germination and growth of micro vegetables. The material itself is very thicken compared to other mats. But the major downsize that we see is if you don’t handle with care the material itself strikes. And you can’t sow seeds evenly as you should. And you can end up with lot of seeds in one place, which could lead to mold. I have grown some tests at the beginning of our microgreen business, and I know that growing is not the same as it is on the soil. Yield is much smaller and the growth is slower. In general all the soil alternatives, if you don’t add them any nutrients, get slower germination and growth and lots of times this also affects the lower final yield of the microgreens. If you want to try rockwool you can buy it here on Amazon.
Rockwool mat for microgreens.
You need to moisten well mats with water first. The material absorbs and retains water better than soil. Roots will receive ideal water wickling while being supported by the textile without being crowded. Roots easily penetrate the textile and produce thick root growth under the mat. You will need to work less with them. This material will not deteriorate during the growth. So you are assured that post-harvest microgreens will not contain any loose fibers. Neither will your water filters become clogged. The fibers used in this product will not dissolve in the water. This material will also not add any unwanted substances nor alter the pH of your water during the growing of your microgreens, both which affect the nutrient value and taste of the final product. But have in mind, than when growing commercially it is recommended to add nutrients in the final growing stage.
We found this one Growfelt: http://www.growfelt.com/growing-media/.
Polyroot grow mat.
Growfelt grow mat.
Biostrate grow mats
BioStrate Felt maintains its value because it consistently provides an ideal environment for adolescent roots. It has been certified internationally for bio-based elements and the ability to biodegrade. Biostrate pads are biodegradable and can be composted in industrial composting facilities but not recommended for backyard composting.
BioStrate Felt soaks in water with its thick fibers, granting an optimal environment for young roots. A combination of biopolymers and natural fibers is designed to effectively control water, allowing seeds to thrive in a variety of hydroponic methods. BioStrate is clean and won’t clog filters. There are different thickness available, so consider which one you need (big seeds need thicker mat). They are available here.
Biostrate grow mat.
Now it’s time for 100% natural biodegradable materials. You will see, there are several mediums already available on the market. You just need to pick the most convenient for you.
It’s quite similar to grow microgreens compared to soil, also with mess around if you want to cut it in your size. Otherwise it’s very easy to cut it with regular scissors. Since it is made of 100% natural material, it is very easy to dispose and compost. When you sow lighter seeds on this material they are less visible (when you need to sow very small amount of seeds, this could be tricky).
However, microgreens can alter in its taste, regarding this medium. You can get it here.
Mess around when you cut hemp mat.
Jute is a fibrous plant that has been used to make rope and textiles for hundreds of years. Jute grow pads are made of 100% all-natural woven jute fibers with no binders or fillers. They naturally wick water and have a high water holding capacity. These microgreens grow pads are fully compostable. Perfect for growing microgreens and wheatgrass hydroponically. Disadvantage is that it is expensive if not re-used. But they said that it can be re-used by sterilizing in boiling water. I would assume, that you also can end up with a mess if cutting on your own dimensions. You can find them here.
Some of the people recommend to presoak mats in water for 24 hours before sowing the seeds on them. But our tests shows, that this step it’s not needed. The structure of the mat compared to hemp mat is much more sturdy. That’s why it is more appropriate for the smaller seeds like broccoli, radish and not for bigger seeds like sunflower, pea. It holds water very well, so you need to be careful not to overwater it. The downside for us was, when we want it to be precut in our trays, we end up with a lot of mess around and the cutting was not so easy as with other mediums (I would say that this is also because the material itself its more thick then others but definitelly more sturdy). If there is excess water, you should pour it away. Microgreens can alter in its taste, regarding this medium. There also can be the smell of coco shells. And the price is quite high per tray, for the ones that we bought in the UK, compared to other growing mediums. You can try this one also.
Coco mat & mess around when cutting.
Coco coir (peat)
It’s a waste product of the coconut industry, and is the husk of the coconut itself. Water retention capacity of it is quite OK but it is a large oxygen capacity. One word of caution about coconut fibre- there is a commonly available, lower grade of coconut fibre that is high in sea-salt and is very finely grained. This lower grade coconut fibre will produce disappointing results. So try to find organic coco coir. One of it is here. You need to soak it in water to fluff it back, because it’s compressed. For me, this is a major downside of using this blocks. Although its very handy to get them in blocks but for us the extra work to fluff them back it’s just not working. Plus, I think you need to use all in one or in a few days, because the coco is still wet, after absorbing all the water and it can not be drained out, when you have them in a box. It can get moldy in there. When you grow long therm microgreens, you need to add nutrients. For home growing, you can use coco disc.
Wooden (cellulose) grow mats
Are perfect for those looking to grow wheatgrass, barley grass, microgreens, or other plants, without the hassle of dealing with soil. These mats are made from sustainable harvested wood fiber that is 100% fully compostable. They are produced from sustainably harvested wood and are free from plastic and synthetic fibres.
Keep in mind that when wet, these mats become very fragile. So, make sure they are in place before saturating. We didn’t have it, when we were making tests, but I would assume that cutting them into smaller pieces it’s quite easy and that this will not leave any mess behind the cutting. You can get it here.
Wooden (cellulose) mats.
Pretty new material for growing microgreens. But since it is 100% natural and biodegradable it promises a lot.
They have outstanding water retention (holds 9,5 times its weight in water) and are eco friendly. With that being said, they are very easy to use, after being used, they leave no mess or residue behind. For a faster one, no nutrients needed or pH balance, but for longer growing ones and for better product yield you need to use some. Won’t alter microgreen taste like some other mediums. You can buy them in roll or cut it into smaller pieces. You won’t get any mess, when cutting on your own, and it is quite easy. The feeling of material is like having soft cloth in hands. That is why you need to be careful when placing material in the tray. Place it as evenly as you can, otherwise you will strugle with sowing seeds evenly without catching more seeds in one place. We noticed also during the test, that even if you somehow forgot to water them, they will stand back if you water them back. Manufacturer: https://www.vegbed.com/products/vegbed-microgreens-mat-pack-of-10?ref=brqia3vhgc4.
I would like to talk a little bit more about soil. The quality of your microgreens depends on the composition (quality) of your potting/seedling mix. So, the better the soil is, the healthier microgreens you will grow. In fact, poor soil can result in a lot of growing problems, which include mould, inconsistent growth or even crop failure. Since microgreens are such young plants, they absorb nutrients from the soil, which include the organic matter (nitrogen, phosphorus, and potassium) and minerals. Basically, when growing, each seed contains certain nutrients that are meant for nurturing the germinating baby seedlings until they develop enough of their own roots to absorb water and nutrients from the soil.
The nutrients in microgreens come from the seeds. Some of the nutrients contained in the seeds are mostly inactive and cannot be easily digested. When seeds are sown in a medium (soil, coco fibres…) and watered, they absorb water, swell, and allow certain biochemical changes to take place. Then the seed nutrients are converted into easily digestible forms for young seedlings to take up and grow. In addition, certain enzymes and other bio-factors are also produced to help nourish the young seedlings. All these make microgreens richer in vitamins, minerals, and enzymes and bio-factors than the seeds from which the microgreens are grown.
If you have the option, we prefer to use organic soil, like this one or these. If you have an option for Klassman soil, we use this one: https://klasmann-deilmann.com/en/competencies/substrates/easy-growing/#organic-horticulture. Try to find some with a mixed composition (compost in general, with some peat moss – but not necessary; perlite and vermiculite are also an option, but they are not necessary). Commercial potting soils or seedling mixes are pasteurised and sterilised to decrease the risk of contamination. But if you decide to try growing microgreens using soil from your own garden, you should first sterilise it by baking it in the oven at 212°F for at least 39 minutes.
Our hint is to spread the soil as smoothly as you can in the tray. This will enable the seeds to spread evenly around the tray without getting stuck in little holes and rotting (if the soil was not nicely smooth and flattened).
Factors that help you determine which growing medium is your best choice.
- Growing space
Do you have enough space for soil/coco coir (peat) and are you bothered with using them in the kitchen? Will you grow indoor or outdoor? This depends on your area and environment conditions. But have in mind that if you want to grow the whole year round, you need as much constant conditions as possible. More details on this you can read in this post.
- (Extra) labor
Does choosing growing material need some extra work like coco coir or soil? Or do you just place it in the tray, without any mess. If you want premium final products then sometimes you need to put some extra labor into the growing process. What you will see is that if using soil, there is a little mess around it, but the final product is a premium one. To have less work with soil, and to have the same quality of the soil each growing time, we do recommend to use already commercially prepared soil. You can choose this one. If using a more clean version – of growing mats, this doesn’t require extra work with soil, because you just place the mat in the tray, moisten it very well and that’s it.
How much water does your growing medium absorb or retain? Soil does need daily watering and most mats don’t need it on a daily basis.
Does the growing medium itself have enough nutrients to support microgreens from the germination to the harvest day? Like soil or there need to be added nutrients, so that microgreens will get better yield when harvesting, like with mats?
- Final customers – requirements (*for commercial growers)
Who are your final customers? Restaurants and chefs or households and grocery shops? What are requirements for public kitchens in your state, where you live? If you can sell living microgreen on the soil also to the public kitchen, this is a good choice. But if the state doesn’t allow soil to be present in the kitchens, then growing mats are a good solution to this.
- Final product – yield & living one or harvested (*for commercial growers)
Do you want to get the best yield from the tray? Are you selling living ones in the trays and the government allows you to sell them with soil? Or do you cut microgreens and pack them in clamshells? If you are doing so, then soil is most recommended, because the growing medium will stay at your place and you will sell just microgreens. Just be aware if you don’t wash them before use, you need to state that on the label (*wash before use). In many cases with this approach you comply with government regulations.
At the end of the article I will combine all the mediums and evaluate different factors based on OUR opinion. 5 is meant for good choice/option, 1 for poor choice.
Different growing mediums.
Our evaluation on different growing mediums.
*soil / coco coir/ coco discs: we put less points to the growing space because sometimes people are not suitable with the usage of the soil in apartments (the same goes with coco coir). Some extra labor is required for preparation of the soil (especially if you didn’t buy the final mix already, then you need to mix it also) and if you bought compressed coco, then you need to put it in the box and fill it with the water to fluff it again. Less work is for home growers if they use coco discs. Watering is essential for growing on the soil/coco, because they do require daily watering. That’s why there are fewer points. We gave full points for final customers if you can sell them living microgreens on the soil or if you are cutting them. If the government requirements are different, then here would be less points. When it comes to cost effectiveness, soil and coco coir are the cheapest growing mediums calculated per tray (we calculate for 10’’x 20’’ standard US trays).
*different natural mats: they do get high points, because they don’t require so much extra labor. What is needed is you are buying this material in rolls, then you need to precut it in the tray size. For growing space they get 5 points, because if you buy mats, all you need to do is to place them in the tray. Without preparation of the growing medium. These materials in general absorb and retain water very well, which means less work with watering during the growing process. The down side of these mats is that they require adding nutrients if you are a commercial grower. So this is an extra cost. Downsize is also, that if your microgreens get drained, only on bamboo mats we could bring microgreens back, with other materials don’t. They die. Regarding final customers, some people don’t want microgreens to be grown on the mats and do require soil, because it is the most natural medium. But if you are selling microgreens to the chefs, in some countries this could be an advantage. For final products, the yield compared to the ones grown on the soil is definitely lower one, but if you add nutrients to the water, then the yield becomes much higher. When comparing the cost of the mat for one tray with soil or coco, it is more expensive (see in the table).
Sowing garden cress on different groing mediums:
upper row from the left: hemp mat/rockwoll/coco mat/soil
bottom row: bamboo mat/presoaked coco mat/coco peat.
Our final conclusion is that we really love soil the most and how microgreens grow on it. They do perform the best in our test, they grow faster on soil (one day faster), and the yield is bigger with soil and the coco coir also. So since here in Slovenia, we are allowed to sell living microgreens grown on soil, we do prefer this method. But if we would need to switch one day to another growing medium, we would use natural mats – bamboo/jute/hemp mats. Because of their overall performance with microgreens. But with the mark here* – this is for fastest one grown on mats, but for larger seeds, and longer growing varieties, you must add nutrients to the water. See below, why. Especially this can be seen on shiso, where the growth itself without added nutrients stagnate, and leaves becomes yellow.
Sunflowers on different growing mediums:
upper row from the left: hemp mat/rockwoll/coco mat/soil,
bottom row: bamboo mat/presoaked coco mat/coco peat.
Sunflower, day 6.
Pea on different growing mediums: upper row from the left:
hemp mat/rockwoll/coco mat/soil, bottom row: bamboo mat/presoaked coco mat/coco peat.
Pea, day 6.
Pea , day 9.
Shiso on different growing mediums: upper row from the left: hemp mat/rockwoll/coco mat/soil, bottom row: bamboo mat/presoaked coco mat/coco peat. Day 13.
Closer look on shiso on different growing mediums, day 13.
We have tested on this materials also larger seeds (sunflower and pea) and the one (shiso), that grow longer time. It is a must to use nutrients in the water, otherwise your products will grow much slower, and the yield, or final product will not be the same (or lower) compared to the one grown on soil,. This refers to all other materials, that we used in the test, except soil. I think pictures below will answer pretty well on this issue.
What about watering?
Watering microgreens is one of the most important things when you are a professional grower. Everything depends on which growing medium you are using.
Teach your customers how to handle microgreens grown on soil, and you will have happy customers/chefs
Soil is a growing medium that all plants, whether they are grasses, flowers, trees or vegetables use in nature. When you look at the nutrition perspective of nature compared to other no-soil growing mediums, in the soil nutrients are already present. For other non-soil mediums, you need to add them manually, but if we are comparing soil vs non-soil, non-soil definitely has an advantage when we are talking about watering. Our tests showed that microgreens grown on the soil are more beautiful than on others but needed more careful watering. Soil is drying faster and you need to water daily. Some of the other growing mediums have characteristics like a sponge. And they don’t require daily watering.That is why if you are growing on soil it is super important to water them very well, before you deliver microgreens to the restaurants. And the very first thing is to teach your customers and chefs how to handle microgreens, if you are selling them living ones. We here in Slovenia are selling living ones, grown on soil to restaurants with no problem. But you might live in a country that doesn’t allow selling microgreens grown on the soil, then you will need other mediums. How to choose your second best choice, we will help you with more details of each medium that we found present on the market.
As you might know, conditions in public kitchens are very much different than in homes. There is a much higher temperature which leads to dried soil faster. There is an option – they can place microgreens in the refrigerator, but they need to be placed on the shelf that doesn’t have a fan. With this they will last at least for one week till two weeks, and watering is needed just two times per week there. But when you take them out, they again need daily watering. If you don’t teach your chefs how to handle them, microgreens then could easily fall down because of lack of water which is a normal response of the plants. But this can result in some bad feedback from the chefs. That is why, firstly teach them how to handle them and you will have a win-win relationship. You will get the feeling of how much you need to water – because too much water is also bad and it can damage roots if they stay in the water too long or they can get moldy.
Me watering our microgreens.
Our youtube video on different growing mediums.
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