Microgreens are becoming a sought after new product. They are well known by chefs of leading restaurants, but the average consumer has not had access to them until recently.
They are very much like sprouts, but they differ in that they are grown in the light, not in a dark, enclosed environment as are sprouts. Sprouts may be greened for a short period of time, up to about 12 hours for alfalfa, radishes, etc., but not Mung bean sprouts that are grown in the dark for their whole life cycle of 4 to 5 days. Since microgreens are grown in the light they are more nutritious than sprouts due to the photosynthetic products in the plants. For example, red pigweed or Amaranth is a red microgreen high in anthocyanin pigment similar to beets. This is a healthy source of vitamins and minerals.
Microgreens are establishing a niche in the supermarkets of North America and Europe. They are grown in small plastic containers with sleeves or clam-shell plastic containers and are relatively high priced (Photos 1~2). For restaurants using a larger volume of such products they can be grown in trays and delivered directly to the restaurants in situ still growing. They are very perishable so cannot be cut and then sent to the end user.
How would you like to grow your own microgreens in your home? It can be done at a low price compared to purchasing them in clam-shell containers. And they can be grown within 6 to 10 days depending upon the specific plant! Let me show you how to do it.
First you need to purchase the correct seeds. These can be purchased from popular garden seed catalog companies, such as Johnny’s Selected Seeds. Check out the catalog under “Micro Mix Varieties.” You can also find others under the “Herbs” section. They have a box showing, “Herbs for Micro Mix and Salads.” They define “Micro mix” as “a gourmet vegetable confetti made from a variety of crops harvested at the seedling stage.”
Similar to sprouts it is important to be careful not to purchase any treated seeds. That is, do not buy regular seeds that may have been surface treated with fungicides. Purchase seeds specifically listed for use as microgreens. Since these seeds are not treated they may have fungal and bacterial spores on their surface. These pathogens will cause rapid death of the germinating seedlings unless they are eliminated by surface sterilization.
- Seeds – as discussed above.
- Plastic trays (flats): If possible purchase these trays without holes in the bottom. That will conserve water as it can remain in the bottom of the tray. It will also make it necessary to water only once per day. Between crops you can re-use the trays as long as you sterilize them with a 10% bleach solution for 20 minutes.
- Capillary matting or thick paper towels: You may be able to purchase a capillary matting from a hydroponic or garden shop. It is about 1/8-inch thick. A very good one is the STG matting. Alternatively, you can use high quality thick paper towels such as “Bounty.”
- Plastic cup: The plastic cup is used to surface sterilize the seeds.
- Bleach: You will dilute it to ten percent using a measuring cup or by marking the plastic cup in a ratio of 1 to 9. That is, for example ¼” of bleach and then fill to 2 ½ inches with water.
- Spoon: Use the spoon to spread the seeds onto the matting or paper in the tray.
- Hydroponic Plant Food: This can be purchased at a Hydroponic shop.
- Measuring Cup: Use this to dilute your nutrient solution to half strength and to add the water or solution to the tray.
- Lights: Especially during the winter months, use two 25- to 30-watt, compact fluorescent bulbs above the germination tray.
- Timer: Use a 24-hr with hourly increments.
The choice of seeds depends upon their rate of growth, color and taste. Color and taste is really up to you. If you want something deep red you can use Red Amaranth or Bull’s Blood Beets. If you want a spicy taste choose some radishes, purple or green. If you are going to growing a number of different seedlings together in your tray, you need to select ones that have similar growth rates. For example, do not combine seeds that germinate slowly with ones that germinate quickly. The rapid germinating seeds will be ready days ahead of the others and you will need to harvest one before the other. That is not convenient in terms of growing. For example, radish grows quickly. Radish will be ready to harvest in 5 to 6 days, whereas some lettuces or other greens will take at least 7 to 10 days. So, grow radish with other seeds that germinate rapidly.
If you like the beet flavor or Amaranth and the red color you can combine it with some other greens such as cole crops or lettuces. They take about 8 to 10 days. Here are some combinations that we have found work well:
Purple & Diakon Radishes (Photo 3) Amaranth + All Greens (Photo 4)
Amaranth + Mild Mesclun All Lettuce + Mizuna
Amaranth + Spicy Mesclun Amaranth + Spicy Greens
Wildfire Lettuce + Komatsuna
As I mentioned, you need to test some out for yourself and find the mixes you like the most. The Johnny’s catalog lists the micro mixes in two catagories: fast growing varieties and slow growing varieties. So, try to work within these categories and do not combine fast ones with slow ones.
This is key to success as if any infection of diseases enter your trays they will cause dying of the seedlings very rapidly. To surface sterilize the seeds make up a 10% bleach solution (dilution of 1 part of bleach to 9 parts of water) with a measuring cup or graduated cylinder (Photo 5).
Pour the bleach solution into a plastic cup with your seeds (Photo 6). You will have to determine the amount of seeds needed per tray. This brings us to sowing density. The seeds need to be almost touching each other over the entire area of the matting or paper towels in the tray (Photo 7). Of course, you will not get them perfectly even, so some will be touching in spots and spaces will be between clumps of them, but do not pile them one on top of the other.
Stir the seeds in the cup of ten percent bleach solution with a spoon keeping them moving about the solution for about 4 minutes (Photo 8). You may rinse them with raw water.
Pour the seeds through a strainer to remove the bleach/water solution (Photo 9). Scoop the seeds out of the strainer with the spoon and place them evenly on the paper towels in the tray after making the paper towels moist with water (Photo 10). Continue to spread them evenly using your finger. Be sure that you do not touch soil or other dirty areas with your fingers before spreading the seeds as that would introduce the risk of contaminants. If you are mixing seeds in a tray make a distinct straight line with the seeds at the interface of the different seeds (Photo 11).
When moistening the paper towels or matting before placing the seeds on them, do not flood the paper towels. Pour enough water in the trays to reach the bottom of the paper towels or matting. That is usually a level of filling the groves of the trays. If you put too much water in the trays the seeds will float around and clump. Whenever adding water or a dilute nutrient solution do not overfill the trays. Pour the water or solution along the sides of the trays slowly to avoid floating the seeds.
The germinating seeds and subsequent seedlings need light. Place them near a window or on a bench or the kitchen counter and support two 25- to 30-watt compact fluorescent bulbs above the tray. Locate the lights about 12 inches above the tray. The lights should be on for 12 to 14 hours. If you wish to automate the lights, plug them into a simple household light time-clock. For the lights you could purchase several desk reading lights. Replace the incandescent bulbs with compact fluorescent ones.
This is a hydroponic method of growing so you will need to add a nutrient solution to the seedlings about 3 to 4 days after sowing. Use water prior to that time. Begin using a dilute nutrient solution when the germinating seedlings reach about ¼-inch in height. Purchase a hydroponic vegetable formulation from a hydroponic shop. It is easier to use a liquid concentrate. Dilute it to half the recommended strength. If it is a powder, add only half the recommended dosage to the correct volume of water. Store the nutrient solution in an opaque container. A one-gallon plastic bottle would be fine such as an empty bleach bottle. However, rinse the bottle many times until you are sure there is no residual of the product it contained.
Add the water or solution along the side of the tray with your seedlings so that they will not get washed together on the paper towel or mat. Once they have grown about ¼” to ½”, about 2 to 3 days (Photo 12), they will not drift as you water and therefore you can add the water with a little less precision. Do not add excessive water or solution. The substrate (paper towels or capillary matting) must not be inundated with the solution or the seedlings will suffer from oxygen deficit. Keep the level so it just touches the bottom of the substrate. If you add too much you can always pour some off. I have included some photos here of the various stages of growth from 4 to 6 days (Photos 13~14).
The seedlings are ready to harvest when they reach about 1 ½” tall or just to the upper edge of the tray (Photo 15). This stage may vary from 6 to 10 days depending upon the species of plant. With a scissors cut a section of the substrate with the seedlings and remove them from the tray. Then, cut the seedlings just above the surface of the substrate so that you get only the stems (shoots) and not the seed coats (Photos 16~18). Collect them in a bowl and then put them in your favorite salads or dishes to give a nice added taste and touch.
After harvesting the microgreens you may re-seed more in the same tray. But, sterilize the tray for about 15 to 20 minutes in a 10% bleach solution. Rinse the tray and add your paper towels or matting again for the next crop. Repeat the same procedure given above for a new crop.
Don’t be afraid to experiment with different combinations of crops to determine which ones grow best together and which ones have the best taste in your salads, or other areas of meal preparation.
Articles Written by Dr. Haward Resh