There are several answers. The most important thing to understand is that some garden seeds are treated with pesticides, fungicides, or preservatives — chemical or biological. These are to protect them from soil-borne pathogens or to improve storage-life. This in itself is not a bad thing. By the time you plant a pea seed in the ground, water it, and grow it to its full size, the chemical or biological agents are normally degraded and washed away. However, microgreens have a very short seed-to-harvest time. They are also grown in a container instead of in the open air and ground. Additives do not have time to disintegrate. Microgreens are planted and harvested within 7-14 days. Anything on the seed is going to still be on the seed, plant, or soil at the time of harvest.
At The Mighty Microgreen, we search out quality, non-GMO seeds that have been grown specifically to be used as microgreen seeds. We choose organic seed wherever possible. Finding a trusted source is important. Anyone can label seeds as ‘microgreen seeds’ and sell them on Amazon. Unfortunately, the purchaser rarely knows where they are sourced from or if they have been treated. There isn’t the oversight for seeds that we would hope there might be. Buy microgreen seeds from a trusted source and that you know have been grown specifically for microgreens and/or sprouting.
A half- teaspoon of broccoli microgreen seeds should produce a full 5×5 tray of microgreens, not a sparse tray with a lot of dead seeds at the bottom. Microgreen seeds purchased from a reliable source will have been checked for the germination rate. Most will have at least an 83% germination rate, and many have a much higher rate. This simply means that you get more microgreens from your seeds.
Purchasing seed packets from a big-box store often mean that you are getting seed from an unknown source, with unknown additives and an unknown germination rate. Often, local feed stores or garden centers will sell seeds in bulk that are specifically for gardens or fields. These are often treated and the person behind the counter may not be familiar with microgreens and sprouts or understand what is safe for microgreens and what is not.
There is another source for microgreen seeds that may come as a surprise!
When I first began growing microgreens there were no seed companies specializing in microgreen seeds. My source was the local health food store that sold many organic grains and seeds in bulk. I bought lentils, buckwheat, beans, grey sunflower, and any other seed that I thought I could grow. Some grew well, and many were ‘so-so’. Some were completely unsuited for microgreens which I learned from trial and error. If you have a food store that sells raw, bulk seed, don’t be afraid to try them as microgreen seeds. They are often a very economical way to purchase seed.
For sake of safety, purchase seed that is destined to be either eaten as-is or seed that has been specifically grown and packaged for microgreens.