In this blog post I will cover many of the different grow mediums used when growing microgreens and cover some of the pros and cons. Let’s get started with my all time favorite microgreen medium. UPDATE: Soil used to be my favorite grow medium, but that has since changed.
It wouldn’t be right for me to leave out the grow medium I have been using for over a year now, so here I am updating this post! I have found coco coir to be such an excellent choice that I even wrote a very short book about it’s benefits Growing Microgreens with Coco Coir . Though I am going to cover most of what is in that book right here for you!
When choosing a grow medium for microgreens, there are a few basic factors to consider. First is cost, nobody want to spend more than they need to to grow microgreens and if you are selling them you want to keep your costs low and margins high! When purchased in compressed block form, coco coir is very inexpensive, less than half the price of soil. Don’t be fooled by its small size, compressed blocks will really surprise you at how much they expand. A 5 lb block like I linked above will expand to easily fill an entire wheel barrow. It can be purchase in bags already expanded, however it is much more expensive so you lose out on that benefit. Using loose coco coir has been a much different experience than the mats that I talk about below. Water retention is another big factor to consider when choosing a grow medium. Some soils can retain too much water that can lead to mold, root rot and damping off issues. Coco coir retains water very well while allowing the surface to dry out quickly. Since switching to coco coir I have not experienced damping off, even with amaranth which is very sensitive.
One downside of using coco coir, at least the pure coir blocks is there are zero nutrients in it. There is a common misconception that microgreens don’t need nutrients to grow, this is only partly true. Yes there is enough nutrients in the seed to form a root, push up the sprout and form some leaves, but that is about it. To grow nice lush healthy microgreens you will need some form of nutrients, my nutrient of choice is General Hydroponics Max Grow but there are plenty to choose from.
Good old tried and true soil, by far my favorite grow medium for microgreens. There are many reasons to love soil and I will break down exactly what makes this earthly substance the best for growing microgreens. First off, soil is inexpensive. When using a quality soil for microgreens you can expect to pay right around $1 per 1020 tray making this the most inexpensive medium on the list. When using soil to grow microgreens, it’s easier to grow organically when using a quality organic soil, there are movements to designate growing in soil the only organic method for growing microgreens. Soil also holds moisture extremely well, especially if the soil contains a fair amount of perlite making watering a breeze. Watering microgreens when using soil is typically a once a day task. Growing microgreens on soil is also very predictable, I have found soil to be very consistent from one batch to the next and the results are very predictable.
Some microgreen varieties such as sunflower and beets really prefer soil over hydroponic methods. When growing microgreens in soil you wont need to add any nutrients, again making it easier to grow organically as organic nutrients can be difficult to use though for very long term grows like Sorrel a nutrient may be helpful. Soil however does have a couple downfalls, it is messy. Using soil to grow microgreens means more time cleaning and sterilizing trays. Your location is also a factor when growing microgreens in soil because you need to do something with it once you have used it. I pile up my soil outside and allow the microgreens roots to break down then it gets reused in outdoor gardens. Many people do not have the space to pile up soil outside and finding a way to get rid of it could be a problem many people don’t want to deal with. Soil also makes it difficult to sell living microgreens as chefs don’t want or can’t have soil in their kitchens, an understandable request. Therefore soil grown microgreens need to be harvested and packaged when selling to restaurants.
Microgreens will grow in just about anything, though some soils definitely outperform others. The soil I use the most is ProMix BX series Promix BX this soil is light and fluffy, characteristics I look for in a microgreens soil. This is also an easy to find soil and is carried by many gardening stores and hydroponic stores. I also really like Sunshine Mix #4 this mix is loaded with perlite and is a fantastic choice for microgreens, this might be my favorite soil though it’s a little harder to come by in my growing location. An organically listed soil that works great would be Black Gold this is just an all around great soil for Microgreens and can be found fairly easily, even at some Ace Hardware stores. Soil can be found in any big box store and will grow Microgreens just fine but the ones listed above are among the best in my experience.
My second favorite grow medium for microgreens is hemp. Hemp grow mats are very similar to soil in many ways. The hold water fairly well but will need to be watched more closely than soil. I have found when growing Microgreens on Hemp mats nutrients were not necessary though they may help. You can grow on hemp and call it organic though nothing is more organic than soil. When growing Microgreens on hemp, you can sell live microgreens to restaurants as it isn’t “Dirty” and can be brought into the kitchen. In my experience growing on hemp is consistent as compared to soil, you can easily predict how the crop will come out. Hemp can also be composted down like soil and reused in outdoor gardens or it could be disposed of in the trash if you are growing a small amount, a little hemp in the landfill wont hurt anything and could actually be beneficial. Growing on hemp does require a little more attention than growing on soil as it can dry out faster, watering may be needed more than once a day. Hemp is fairly expensive, more than twice the cost of soil. The cost of growing Microgreens on hemp is the biggest reason I prefer soil.
I have used these Hemp Mats and have found them to be excellent.
Coco Coir is fairly similar to Hemp and is a great alternative to soil. Coco Coir tends to be more expensive than soil and while fairly easy to find it is more difficult to find than a quality soil. The only thing I have found different from hemp is that added nutrients seem to be more necessary than with Hemp mats. Coco Coir comes in a lot of different varieties. You can get it compressed where water is used to fluff it back up Compressed Coco Coir or you can get it as a mat where its woven similar to the Hemp mats Coco Coir Mats Coco Coir mats are typically considered a clean way of growing and live Microgreens can be allowed into a kitchen when grown on Coco Coir.
Biostrate is a woven mat felt material. Biostrate could be a good option if you do not have the room to dispose of soil. Biostrate is considered a clean method and should be allowed in most kitchens. Biostrate is pretty thin and easily disposed of after growing on it. In small quantities it is about 50% more expensive than a quality soil. I have found that Biostrate absolutely requires the use of a nutrient supplement in order to get a decent crop. Some crops such as beets and sunflower really struggle to grow in Biostrate and anything that is not soil. Biostrate requires a very careful monitoring of watering, it can dry out very quickly. If you want to give it a try find it here Biostrate Mats.
These are mats I had very high hopes for. The main reason I so badly wanted them to work is the cost. Wood fiber grow mats when bought in bulk are very similar to the cost of soil. These mat have a consistency very similar to several paper towels stacked over each other. One of my biggest issues with these mats has been mold growth, I have had to completely toss out several trays because of mold with these mats. I have heard of others that enjoy these mats so I don’t want to be completely negative here but for me they just haven’t been good. For that reason I will not be recommending them or showing a list of pros and cons for these.