I buy my seeds for microgreens from Johnny’s Selected Seeds, and they have a great article on their web site called the “Guide to Year-Round Microgreens Production” that I wanted to share:


The article includes planning, sowing, growing, harvesting, and marketing. The method they use may be different from the method I use; however, many of the steps are the same. Here are some tips in their article that may help others have the most success with microgreens.

Seed Density and Germination

For the floating tray technology I use to grow microgreens with the Speedling tray, I recommend that you follow the rule of thumb for seeds from the place where I buy my seeds:

“As a rule of thumb, sow small seeds at a density of approximately 10–12 seeds per square inch of tray surface, and larger or medium-sized seeds at a density of 6–8 seeds per square inch.”

I use the Speedling soil-less media, cover the seeds with a light layer, and then water gently. It is necessary to cover the trays to keep the media from drying out for 2-3 days while the seeds germinate. Those trays that sit in our pans may be covered with a sheet of plastic across the top of the pan. Keep the lights off during germination.


Our system requires that the building heating, ventilation, and air conditioning (HVAC) system regulate the temperature, air flow, and humidity. Our system may be installed inside a grow tent or clean room with a separate HVAC system. Here is the recommendation regarding temperature for both germination and for growth:

“Optimal ambient temperatures are also variety-specific, but 65–75°F/18–24C° is generally a favorable range. Temperatures above 75° can increase disease pressure and inhibit germination in some varieties.”


Since microgreens lose much of their taste and nutritional value in 1 or 2 days after harvesting, I recommend that you do not harvest what you do not eat that day. You can cut with scissors what you want to eat whenever you want to eat, and keep the remainder growing for the next meal. As for when the microgreens are ready to harvest, here is a tip from the article:

“Microgreens are typically harvested at the first-true-leaf stage of growth, with the cotyledons still attached, or at the seed-leaf stage, at heights varying between 1–2 inches.”

That’s all for now. Happy urban agriculture!!!


Farmer Jim

Jim Ray, President/CTO & Founder
NetZero // Urban Agriculture – Grow Love. Feed. Every. Body.
office: 855-636-9114 cell: 984-459-0458
email: jim@hq.net0ag.com web: www.net0ag.com