Broccoli is the greatest microgreens of all time. Not only are broccoli microgreens the healthiest microgreens in terms of health benefits, but it's also one the more affordable microgreens to grow.
Broccoli microgreens contain 5 to 10 times higher concentrations of antioxidants such as glucosinolates and sulphoraphane versus mature broccoli (1). Moreover, broccoli are rich in Vitamin A, B, C, E, K, as well as iron, potassium and selenium. Broccoli roots are known to sequester selenium in the soil.
Compared to other microgreens, broccoli has the second highest concentration of antioxidants, just behind peas. However, broccoli has the second highest concentration of myrosinase in the brassica family, which is an enzyme that metabolizes the antioxidants into toxic byproducts. Fortunately, this enzyme is deactivated by heat. Cooking broccoli microgreens maximizes the cancer-fighting benefits while lowering its toxic byproducts.
For more information on the health benefits of microgreens, please reference my previous article on microgreen health benefits and microgreens safety.
To grow broccoli microgreens, we use use a peat based soil-less growing medium mixture. The base of the mix is peat moss, which comes dried and compacted. To enhance moisture retension and availability, vermiculite is added to the peat moss at 10% by weight. Finally, for improved growth and yeilds, we add synthetic fertilizer to about 0.5% Nitrogen by weight.
Select a container that is at least 1 inch or 3cm in depth because you're growing broccoli for about 2.5 to 3 weeks. You must vigorously mix the growing medium with water prior to seeding because peat moss floats and repels water when dry. This makes it difficult to water after seeding. You may want to have deeper containers for longer growth periods.
There are many ways to sprout the broccoli seeds. Soaking broccoli seeds prior to seeding is optional. According to data in my study, soaking the seeds for three hours will speed up germination by 1 day. The difference in the final result is minimal.
Pre-soaking the seeds is not necessary. Cover the seeds with 1/2 inch of growing medium to provide proper moisture.
The highest reccommended seeding rate is approximately 55 g per square meter or 1/8th ounce per square foot. At this point, the seeds are tightly packed and may clump with one another. If not given enough depth, then the microgreens will likely stunt due to lack of space. Even with this high seeding rate, you can grow 100 square foot with 1 pound of broccoli seeds. Broccoli seeds are sold at approximately 14 dollars per pound. This makes it extremely cost-effective to grow broccoli microgreens.
Depending on the humidity of your environment, you may water up to three times a week. However, even in winter time (low humidity indoors), peat medium will completely dry completely in about a week. Once dry, it's very difficult to re-water. It's reccomened that you water at the halfway point before the medium completely dries.
Fungus is a major issue for growing in high densities. To prevent fungus, water your plants less frequently and keep the humidity low. Plants have a better defense for underwatering then overwatering. Overwatering will not only cause fungus, but prevent oxygen absorbtion in the roots.
After 3 - 4 days, the broccoli microgreens should begin germinating. The leafs should be a distinctly heart shaped, a unique identifier for brassica family of greens, including kale, radish, and arugula. Broccoli microgreens will be around 1/2 inch or 1.5 cm at this point. The flavor profile has a more burnt caramel undertone.
After 2 weeks, the first true leaf should emerge. At this point, you can begin to differentiate between the brassica microgreens. In my opinion, broccoli greens tastes the best when the first leaf is fully formed at around three weeks.
While you can grow microgreens further, I find that the leafs will increasingly taste more bitter after the first true leaf and requires a much lower seeding rate.
Harvesting broccoli microgreens is really easy. To preserve and re-use the growing medium, it's easier to pull the microgreens straight out of the container instead of cutting them. Removing roots from the growing medium is difficult if you were to cut the microgreens with scissors. Make sure to wash your microgreens thoroughly to remove any microbial contamination.
The growing medium can be re-used for the next growing cycle as long as you either re-mineralize or re-fertilize the medium. If there were fungal problems, then you might want to consider composting the growing medium or sterilize it with an autoclave. Peat moss is a good source of carbon for composting. Alternatively, spent peat moss will be good for lawns because it decreases compaction and stimulate root growth.
I am the author of this website and owner of growyourmicrogreens.com. I am an hobbyist gardener and a passionate scientist. I was trained as a scientist in the Molecular Genetics program in University of Toronto, where I received my Masters of Science and published a journal article.