Updated: Mar 13
While most of us know the best way to grow micro greens is in a 10X20 tray, The big question is: what do I line the tray with? And, like everything else in agriculture, the answer is... it depends.
A few of the more popular grow media substrates for microgreens are:
Soil -- Although messy, soil produces the best yields and product. We like Sunshine #4 by Sunshine Aggregate the best and Happy Frog by Smart Naturals is a close second. These are the most sterile soils on the market and ideal for indoor growing. The coolest part about these soils is no nutes needed. Only water and PH down with a splash of fulvic acid diluted at the following rate (.25 ml / 4 litres). Fill up your 10X20 tray about 1” thick. Although ideal for growing all varieties, it makes a big difference for colorful varieties like Amaranth and Bulls Blood. Good soil isn't cheap, expect to spend around $1.00 per tray for either of the soil mixes recommended. With a good compost and sterilization program, your soil can be reused, which will drive the cost per tray down to competitive levels.
Burlap -- At .25 per tray, this is the most economical alternative, but also the most unforgiving which can lead to inconsistent harvests. With perfect conditions, 72 F and 50% humidity, and a good fertigation plan (fertilizer + irrigation) a grower can achieve yields and results with burlap that are similar to soil mixes. However, there is a lot of execution risk with this substrate and your overall average yields will suffer as a result. Varieties with large seeds like Pea Shoots or Wheat Grass grow beautifully on burlap yielding ~12 ounces per pad in a wide range of environmental conditions.
Coco Coir -- We like the Roots Organic compressed Coco Fiber. The Coco stays moist and due to its consistency you can’t really over water it. Coir is less expensive than soil but just as messy. We found that coir can increase yield nearly 25% to 35% over burlap, but it is nearly 2.5X the price at .60 per tray. Coir is excellent with ebb-flood systems.
Hemp mats -- Peel these mats into two pieces to generate the best results. It cuts the cost in half (.65/tray after splitting), and makes it easier for the roots to pop through. The hemp mat holds water really well which decreases the amount of feedings per day. All microgreen varieties grow really well in hemp, especially Kale and Broccoli.
BioStrate by Grow-Tech-- We have had trouble growing with biostrate because it does not absorb water properly, drying too quickly. We also have had issues figuring out what it was made of. At .86 per tray, it was difficult to grow profitably.
*To help make your decision about media, answer the following questions.
1) How will I feed by my plants? For hand watering operations, soil and coir are the best choices. If you have the ability to feed on a timer, burlap might be a better option due its low cost.
2) Where do I buy my seeds? We buy our seeds from Todd's Seeds - Todd’s Seeds specializes in good, old-fashioned, Heirloom, non-gmo, open pollinated vegetable, flower and sprouting seeds. Johnny Selected Seeds - For more than 40 years Johnny's Selected Seeds has been helping families and friends to feed one another.
3) Do I soak my media before use? Not all media, the media that should be soaked before use is hemp mat, biostrate, and burlap. Soak with filter water for a hr or so.
4) What tools and materials are required? Bucket, Gloves, Safety goggles, Spray bottle, ph strips, chlorine test strips, This is just a basic list; depending on what media you choose, you might need other materials or equipment.