Once the growing season is well underway, you may find yourself strapped for time when trying to plant flats of microgreens indoors. This is what happened to Curtis Stone, as it was getting harder to find time to plant microgreens indoors, his demand was staying consistent, so he needed to find a way to plant them in a timely manner outdoors.

Thus, outdoors microgreen planting using The Board Technique was created.

Let’s learn how The Urban Farmer developed and fine-tuned his technique so that we may learn from it as well.

Starting Out

At first, Curtis started to direct seed his microgreens in the ground using the Earthway seeder. This worked OK, but it was inconsistent.

The dates to maturity (DTMs) were not consistent during the spring and fall and the yield was very small per square foot of area compared to growing in flats.

So he decided to come up with another way to plant his microgreens outdoors.

Since Curtis was already soaking and germinating his seeds indoors for flat production and growing them in high tunnels on T-hangers, he figured why not combine the two techniques and use some of growing in trays to growing on the ground.

Benefits of Growing Microgreens Outdoors

The main benefit of growing microgreens outdoors is that they take considerably less time to plant.

One 6ft bed, which is equivalent to the size of 10 flats, can be planted in minutes.

As well, planting outdoors saves on soil mix since you are using the soil on the ground.

Another awesome benefit is that microgreen residue helps build massive amounts of organic matter into the soil.

Microgreens do not pull nutrients from the soil. A plant at this stage is solely relying on stored energy from its seed and the first photosynthesis that occurs.

Because of this, Curtis has been able to plant on the same beds over and over again by rototilling or hand-turning leftover residue and replanting.

Over time, all of the residual organic matter has helped build up the structure of his farm’s soil.

This is like getting the benefits of green manure while making a good profit at the same time!

The Board Technique

The board technique uses 30-inch x 6-foot sheets of plywood with two 6ft two-by-fours on the sides of each board.

Curtis plants on a 15 sq ft. area (roughly the same area as 10 flats).

The seed is soaked and rinsed exactly the same way as indoor microgreens, and the board is placed over the seedbed in the same way as empty flats placed on top of newly planted micros.

You can check out this article for more info.

The board helps to germinate the crop quickly and establish a perfectly level crop.

Curtis places a board on top of the newly seeded crop and lifts it up after 4 days.

Then, the board is taken off, the crop is exposed to light, and will be mature in 5-7 days, depending on the time of year.

The stages of growing microgreens outdoors are nearly the same as flat-based micros, but they do differ a bit, so here is the method:

1. Sterilize The Seed

Sterilizing seed is most important for sunflower seeds, as they have the greatest chance of fungus developing.

Before Curtis soaks the seed, he mixes 4tsp of white vinegar and 4 tsp of food-grade hydrogen peroxide in one quart of water and soaks the seeds for 10 mins.

Then drain and rinse them.

It is recommended by some health authorities that all soaked seeds be sterilized.

2. Soak For 6-8 Hours

After sterilizing, soak seeds for 6-8 hours. This can be done overnight, then rinse in the morning.

For pea shoots, he soaks 12 ozs of seed per flat, for sunflowers 6 oz per flat.

 3. Drain and rinse

Thoroughly drain and rinse the seeds after they have been soaked, then put them in a clean bucket.

If you can’t plant them right away, you can delay this process by a day or two by continuing to rinse and drain them a couple of times a day and keeping them in a shady cool area.

4. Prepare Soil For Planting

To prepare the soil for planting, rototill or turn by hand.

There is nothing different here from the usual bed prep techniques, except that you don’t have to worry about amending the soil.

If you are replanting where field micros were previously, you need to make sure your seedbed is free of residue on the surface.

This can be done through no-till, by stirrup hoeing the last of the previous crop, turning it under, then replanting from there.

The tiller is much faster and there is no concern about weeds because the microgreens grow faster than any weed will.

5. Tamp Down and Water

After the bed is prepped, take your board and lay it on the soil.

Walk on it a bit to press down the soil surface to get a firm, flat bed.

Next, heavily water the soil with your watering wand.

6. Plant and Sprinkle A Light Layer of Soil

Now, spread around your seed just as you do with flats.

The only difference is that in the field you’ll dump down a lot more seed.

After that’s done, spread a small bucket full of finely sifted soil over the seeds.

You can use soil from the ground or your own peat-based soil mix. Curtis uses his soil mix because he has found that he gets better germination.

7. Cover With The Board, Tamp Down, and Water Again

Now cover the bed back up with the board, walk on it again, then lift the board back up to water the bed again.

Now, cover it up with the board and leave it for 5-7 days.

8. Uncover After Emergence and Expose To Light

Once the crops have emerged, lift up the board that was covering them and bring the sprouted seeds into the light.

Wait for a day or half a day to water them, as there is still usually a lot of moisture in the soil.

9. Harvest and Wash

After between 5-7 days of being uncovered (depending on the season), the microgreens will be ready to harvest and washed.

outdoors microgreens

Harvesting Microgreens

When harvesting micros outdoors, Curtis uses a very sharp chef’s knife.

He carefully grabs a handful of micros on the flat with his left hand, then cuts with his right.

He cuts as low to the ground as he can, to get as much yield as possible.

Washing Microgreens

You may not need to wash your microgreens if they are dirt-free after harvest. However, if you do need to wash them, this is how to do it.

There are three stages for processing microgreens. This is Curtis’s method.

1. Wash

Curtis starts with 3 totes in front of him, on the surface of his washing table.

The tote to his left came from the cooler, it holds the microgreens to be washed.

The tote in the middle is a medium-sized tote ⅔ filled with clean, cool water.

The third tote on his right is a large tote with holes drilled on the bottom for drainage.

He hangs on laundry bag inside this tote and uses a couple of spring clamps to hold it wide open.

He puts the micros into this bag after he has washed them.

To wash, take large handfuls of micros from tote #1 and dump them into tote #2. 

Swish them around a couple of times.

When washing sun or radish shoots, as you dump handfuls into your washing tote, slick your hands along the surface of the water.

By splashing away from you, you will notice that the seed hulls will build up on that side of the tote.

Now, if you grab the shoots under the water and pull them towards you, away from the hulls, you will have a handful of shoots with very few hulls, and you can dump them into tote #3.

Every so often use a small colander to scoop the hulls off the surface and throw them into the compost.

2. Spin

From here, the laundry bag full of greens from tote #3 goes into the spinner (usually a modified washing machine).

Make sure the bag is evenly distributed around the circumference of the spinner, so the weight is spread around.

Set the machine for a spin cycle and let it run. 

Continue your washing process so you have the next bag ready when the spinner is done.

3. Dry and Sort

Pull the freshly spun micros out of the spinner and dump onto the drying screen.

Spread the micros evenly over the screen, then run the fans at full.

Gently shuffle the greens around on the screen to expose more of the surface to air. Use this opportunity to pick out any bad leaves.

The last remaining hulls should fall through the drying screen as you move them around.

Be careful not to dry the shoots too much, otherwise, they will wilt.

Bottom Line

If you are having success growing microgreens indoors and are strapped for time, give Curtis’s outdoor growing method a try.

Growing more microgreens while saving time planting sounds good to me!

Do you grow microgreens outdoors? Please tell us about your experience in the comments below.

Stay Local,

Kathy & Jon

your friendly neighbourhood growers


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