Microgreen Production Trials
Overall objective – to determine optimum production practices and yield potential of microgreen
production under controlled environment conditions.
Research Questions
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2)
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6)
Optimum media type, type of tray, depth of media
Optimum seeding rates and seeding methods for different crops
Optimum conditions for germination and subsequent growth
Time to harvest, optimum stage and method for harvesting
Yield potential
Material and Labor costs
Trial # 1. Preliminary Assessment of Treatment Parameters
Media - Sunshine Mix#3 (germination mix) consisting of a mix of fine peat, perlite and vermiculite was
moistened then added to a depth of ca. 1 cm into standard plastic germination trays (10”W * 20.5”L * 2”
deep).
Crops
– Mustard seed (to mimic other brassicas like broccoli, kale)
- Alfalfa
- Coriander
Seeding rate – web sources suggest a seeding rate of 5 seeds/sq. in. We calculated the weight of the
required # of seeds/tray (1X) – then doubled it in another set of trays (2X) – as the 5 seed/sq. in. rate
looked thin and the seed was of unknown vigor.
Management – the trays were misted after seeding – but the seeds were not covered. Trays were
placed in a 22◦C room and a black cover was placed over each tray to trap in the moisture. Once the
seeds were germinated, the covers were removed and the trays were moved under fluorescent lights
(6500K cool white) – with the lights on for 18h/day. The light intensity at the height of the microgreens
was 110 umol/cm2/s-1. The relative humidity in the room was about 90%
The crops were harvested once they had at least 1 true leaf formed. Scissors were used to cut the
seedlings as close as possible to the media surface. The harvested plant material was weighed and the
plants sampled for flavor and texture.
Results
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Day 2 - the mustard and alfalfa had germinated – but were left in the dark to try to
encourage a higher germination %.
Day 4 - alfalfa and mustard were moved under the light. This was too late as the plants had
started to stretch in the dark – and no additional germination was observed relative to 48h.
Day 4 – Day 6 – misting once daily.
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Day 6 – trays had to be re-arranged under the lights to prevent plants along the less
illuminated edges from stretching towards the light.
Day 6 onwards – shift to bottom watering as misting was not supplying enough water.
Bottom water = place the microgreen tray into a shallow tray of water – let it sit for 10
seconds – remove and move back to the light rack.
Day 7 – coriander ready to move under the lights. Only about 50% germination of the
coriander, with many moldy seeds.
Day 7 – alfalfa and mustard have nicely formed cotyledon leaves – but still small.
Day 8 onwards – standard management of all crops.
Day 18 - Crops ready to harvest.
Yields
Mustard
5 seeds/sq. in. yields ...... 67 g/tray
10 seeds/sq. in. yields ...... 71 g/tray
Alfalfa
5 seeds/sq. in. yields ...... 19 g/tray
10 seeds/sq. in. yields ...... 31 g/tray
Coriander
5 seeds/sq. in. yields ....... 25 g/tray
10 seeds/sq. in. yields ....... 53 g/tray
The higher seeding density plantings looked better in all cases (more dense and uniform) and produced
higher yields.
Quality
The alfalfa looked a little leggy, spindly if harvested at the 1 true leaf stage. It was also very
chewy by this stage. The flavor was mild, grass like.
The mustard looked good at the 2 true leaf stage but it was also a little tough if allowed to grow
to that stage of maturity. The flavor was very strong – horseradish like.
The coriander looked very good through to the 1 true leaf stage. It was still tender and had a
very strong coriander flavor. However, the seed coat was often stuck on the cotyledons – this
was unattractive.
No obvious differences in quality were observed between the two seeding rates for any of the crops.
Labor requirements
5 minutes to rinse the tray, fill with media, compact, seed, mist, then cover.
0.5 minutes/tray/day was required for daily maintenance over the 18 day production period.
5 minutes/tray to harvest – this step should be examined to identify more time efficient
techniques.
Total = approx 15 minutes/tray
Conclusions
For a first run through this trial went quite well. The production system worked well and the plants
grown were acceptable – with no major quality issues aside from the fact that the alfalfa and mustard
should have been harvested earlier. A method for removing the seed coats on the coriander would be
useful and a more time efficient method of harvesting also needs to be identified.
Recommendations
10 seeds/sq. in. is superior to lower rates – and higher rates should be tested.
Minimize the period in the dark after seeding to keep the seedlings short.
It appears that the seeds do not need to be covered – as long as a cover is placed over the trays
to retain moisture during the initial germination stage.
Misting does not supply adequate moisture once the plants are moved under the lights.
Bottom watering is effective and only takes a few seconds/tray. Could reduce the required
frequency of bottom watering by increasing the thickness of the media – but this would increase
media costs.
Waiting until the crop has reached the first true leaf stage may increase yields – but quality was
compromised.
Find a better way to harvest than grabbing a clump of seedlings and cutting off with scissors.
Using the deep trays really interfered with use of the scissors.
Mustard (left) and coriander (right) seeded at 5 seeds/sq. in.
Coriander at 1 true leaf stage
Trial # 2.
Increased Seeding Rates
Trial #1 showed that 10 seeds/ sq. in. produced better yields and comparable quality than the
recommended 5 seeds/ sq. in. Trial #1 also showed that delaying harvest until the crop was at the first
true leaf stage resulted in unacceptable quality in some crops. This trial tested higher seeding rates and
an earlier harvest.
Methods
As previously outlined except ....
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Seeding rate of mustard was 10 and 15 seeds/sq in.
Seeding rate of alfalfa was 10, 15 and 20 seeds/sq in.
The seeds were covered with a light layer of sifted peat moss
Trays were only covered for 2 days then uncovered and moved out under the lights
Trays were harvested at 12 days after seeding rather than 18 days as in Trial #1.
This earlier harvest was designed to improve quality.
Results
Germination of both crops was very fast and a very high germination % was achieved. The crops looked
healthy for the entire production period.
Yields
Mustard
10 seeds/sq. in. yields - 89 g/tray
15 seeds/sq. in. yields - 104 g/tray
Alfalfa
10 seeds/sq. in. yields - 56 g/tray
15 seeds/sq. in. yields - 70 g/tray
20 seeds/sq. in. yields - 72 g/tray
A seeding rate of 15 seeds/sq.in. appeared sufficient to produce peak yields in the alfalfa. The higher
seeding rate also improved mustard yields – but still higher rates should be tested.
It is noteworthy that the yield achieved in this trial harvest at 12 days exceeded the yield obtained in
trial #1 which was harvested at a more advanced growth stage (18 days). By using higher seeding
densities, good yields can be achieved (but at an added cost of seed).
Quality – earlier harvest improved the quality of both crops. The alfalfa was less stringy. Its flavor was
still mild/grassy. The mustard was also more succulent than when harvested at 18 days. It still had a
very strong horseradish flavor.
Conclusions
Higher seeding rates gave better yields with no negative impact on quality. Alfalfa appears to reach
peak yield potential at 15 seeds/sq. in. Higher seeding rates should be tested with mustard but will
likely see declining returns on seed investment. Harvesting at the first true leaf stage improved quality.
Alfalfa at 10 seeds/sq. in. (left) and 20 seeds/sq. in. (right).
Trial #3.
Different Tray Types for Ease of Harvest
For trials #1 and #2 seeds were grown in 2” (5 cm) deep trays – this made the plants difficult to harvest
using a pair of scissors – as the rim of the tray interfered with access to the plants. This trial tested a
shallower type of tray in order to improve ease of harvest.
Methods
As previously outlined except…
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Crops were seeded into a 406 celled tray – these trays are the same L and W as those used
previously – but they are only 1” (2 cm) deep and have no edge. Each tray is sub-divided into
406 cells. These trays were filled with moistened Sunshine Mix #3 as previously described.
Mustard and coriander were seeded at densities of 20 seeds/sq. in. and alfalfa at 25 seeds/sq.
in.
Dill was added to the trial and seeded at rates of 23 seeds/sq. in or 30 seeds/sq. in.
Mustard and alfalfa were harvested at 11 days and coriander and dill at 18 days
406 celled tray.
Results
All of the crops germinated well and looked healthy throughout the production period. The dill had a
little bit lower germination rate and like the coriander it had an issue with the seed coat holding onto
the cotyledons.
Harvesting all of the crops with scissors was much easier when using the 406 cell trays.
Yields
Mustard
20 seeds/sq. in. yields - 80 g/tray
Alfalfa
20 seeds/sq. in. yields - 50 g/tray
25 seeds/sq. in. yields - 60 g/tray
Coriander
20 seeds/sq. in. yields - 99 g/tray
Dill
23 seeds/sq. in. yields - 60 g/tray
30 seeds/sq. in. yields - 62 g/tray
The mustard actually decreased in yield at 20 seeds/sq. in. relative to the previous trial where a yield of
104 g/tray was obtained when the crop was seeded at 15 seeds/sq. In. The alfalfa continued to increase
in yield at 25 seeds/sq. in.
The coriander yield at 20 seeds/sq. in. was almost double the yield obtained in the previous trial where a
seeding rate of 10 seeds/sq.in. was used. Dill yields peaked at 23 seeds/sq. in.
Quality – Both the coriander and dill had good flavour but could have been harvested a little sooner
since they were both a bit chewy. Since the mustard went past peak yields at a density of 20 seeds/sq.
in. it looked crowded and much smaller at harvest.
Conclusion
The 406 cell trays filled with Sunshine Mix#3 were easy to manage, allowed for excellent plant growth
and were much easier to harvest than the deep trays. In the 406 trays, the base of the plants were at
the top of the tray making it easy to cut with scissors. The mustard crop reached peak yields somewhere
between 15 and 20 seeds/sq. in. and the dill reached peak yields at 23 seeds/sq. in. Both the coriander
and dill had good flavour but needed to be harvested sooner. A means for removing the seed coats still
needs to be identified for these crops
Mustard (left) and coriander (right) at densities of 20 seeds/sq. in.
Trial #4.
Alternate Types of Planting Media
Plants in this trial were seeded into various types of media with the objective of identifying a media that
allowed good plant growth while also making harvesting easier. Cocomat (coconut coir with a binding
agent holding it together), burlap (sisal fibre) , and “Sure-to-Grow” pads (woven plastic fibres - Crop
King) were tested – as in each case when the crop is mature these media can be lifted out of the tray
and the plants can be easily “shaved” off of the media.
Methods
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Mustard was seeded at 20 seed/sq. in. ;
o on top of a 1 cm deep layer of vermiculite. Vermiculite has excellent moisture retention
capacity.
o on top of a sheet of coconut coir (cocomat).
o on top of cocomat covering a 1 cm deep layer of vermiculite.
o Same as above – except a sheet of burlap was used instead of the cocomat.
o On “Sure-to-Grow” pads.
The crop was maintained as under the conditions previously described. Bottom watering was
used to supply all moisture requirements.
Mustard was harvested on different dates based on how quickly the crop matured on the
various media.
The clear dome was left on top of the mustard planted on the “Sure-to-Grow” pads to conserve
moisture.
Cocomat (left), burlap (middle), and “Sure-to-Grow” pad (right).
Results
The mustard grown on the cocomat and the cocomat with vermiculite underneath germinated well but
then grew very poorly. After 21 days those trays were thrown out because the leaves and cotyledons of
the plants were yellow and shrivelled up. Both the cocomat and the cocomat+vermiculite had poor
water retention so they dried out quickly. The mustard grown in just vermiculite and the burlap+
vermiculite were harvested after 24 days. The plants in those trays also had yellowing cotyledons and
some yellowing leaves. All of the plants on the new media looked stunted and less healthy relative to
plants grown peat-based Sunshine Mix#3. The mustard on the “Sure-to-Grow” pads were harvested at
10 days because they developed surface mold from being covered with clear domes and needed to be
harvested prematurely. They were only at the cotyledon stage.
Mustard growing on cocomat (left) and mustard growing on burlap with vermiculite underneath (right).
Surface mold from leaving plastic domes on too long.
Yields
Mustard
vermiculite
24 days
20 seeds/sq. in. yields - 40 g/tray
vermiculite + burlap
24 days
20 seeds/sq. in. yields - 40 g/tray
“Sure-to-Grow” pad
10 days
20 seeds/sq. in. yields - 36.4 g/tray
Conclusion
All of the different media types were much less productive than growing in peat. The “Sure-to-Grow”
pad should be retested since the mustard growing on it was harvested prematurely due to mold issues
not related to the media.
Trial #5.
Peat versus “Sure-to-Grow” pads
Different crops were grown in either 406 cell trays filled with Sunshine Mix#3 or on Sure-to-Grow pads.
Plant vigour and yields were compared.
Methods
o
o
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Peppergrass (40 seeds/sq. in.), broccoli (40 seeds/sq. in.), and radish (13.6 seeds/sq. in.) were
planted in both peat trays and on “Sure-to-Grow” pads.
Covers were left on until the seeds germinated and then the trays were uncovered and moved
under the grow lights.
The crops were grown under the previously described conditions. The trays were bottom
watered daily.
Microgreens were harvested after 7 days and both yields and quality were assessed.
Results
The 406 cell trays filled with Sunshine Mix#3 outperformed the “Sure-to-Grow” pads in both yields and
plant quality. While the crops germinated well in all media, the plants on the “Sure-to-Grow” pads
appeared to lose vigour after a few days. The “Sure to Grow” pads also retained less moisture than the
peat – this meant that more care had to be taken to avoid having the pads dry out. Daily watering was
required to maintain crop moisture levels using the pads – whereas the peat media retained enough
moisture to last 2 or more days between waterings.
Yields
Peppergrass – “Sure-to-Grow” 40 seeds/sq. in. yields - 93 g/tray
Peppergrass - Sunshine Mix
40 seeds/sq. in. yields - 206 g/tray
Broccoli – “Sure-to-Grow”
40 seeds/sq. in. yields - 176 g/tray
Broccoli – Sunshine Mix
40 seeds/sq. in. yields - 177 g/tray
Radish – “Sure-to-Grow”
13.6 seeds/sq. in. yields - 136 g/tray
Radish – sunshine Mix
13.6 seeds/sq. in. yields - 246 g/tray
Yields of the peppergrass and radish on the Sunshine Mix were substantially higher than on the “Sure
to Grow” pads.
Quality – The peppergrass and radish growing on the “Sure-to-Grow” pads did not look as healthy as
those grown in the Sunshine Mix. The radish cotyledons were smaller/stunted on the “Sure-to-Grow”
pads and were starting to turn yellow and curl. The peppergrass on the “Sure-to-Grow” pads was
shrivelled and starting to turn moldy. In part this quality difference in could be attributed to more
frequent
Harvest – The 406 trays were easier to harvest from since the “Sure-to-Grow” pads are difficult to lift up
and cut from at the same time. A clean surface area to catch the microgreens as they fall off of the pad
also needs to be available. A method for holding up the “Sure-to-Grow” pads, such as using clips and
shaving off the seedlings using some sort of electric knife is another possibility to be examined.
Conclusion – for most crops growing microgreens on peat-based media produced higher yields and
better quality with less attention required to watering relative to growing on the “Sure to Grow” pads
being advocated by some growers/suppliers.
Economics
Based on 5 crop cycles, the economics of growing radish microgreens by either reusing the flats, 406
trays and domes or by selling the crop in the trays (single use) were as follows:
Radish seed at $35.80/lb seeded at 13.6 seeds/sq. in.
Production using “Sure to Grow” pads
Reusing flats and domes 5 times
Selling the crop in the flat = single use
Seed
$11.90
$11.90
Sure-to-Grow pads
$5
$5
Flat tray
$1.40
$7
Clear dome
$2.25
$11.25
Total = $20.55 or $4.11/tray
Total = $35.15 or $7.03/tray
Seed
Peat
Flat tray
Clear dome
406 tray
Production using Sunshine Mix #3 in 406 cell trays
Reusing flats, trays and domes 5 times
Selling the crop in the tray = single use
$11.90
$11.90
$2.20
$2.20
$1.40
$7
$2.25
$11.25
$2.43
$12.15
Total = $20.18 or $4.04/tray
Total = $ 44.50 or $8.90/tray
As the trays represent a major component of the material cost in producing microgreens - the cost of
producing microgreens depends on whether the crop is sold in the tray – or if the crop is harvested
and the trays re-used. Re-using the trays reduced material costs by about 50%. Locating the lowest
cost supplier of tray etc will be important – particularly in situations where the trays are only used
once.
The peat as a production media was less expensive and produced a better crop with fewer problems
with supplying adequate water than the “Sure to Grow” pads – but the 406 cell trays that best suited
production using peat as a media were quite expensive.
Seed represented the single largest cost in producing the radish microgreens. Locating the lowest cost
supplier of seed will be important when growing vegetable crops as microgreens – as vegetable crop
seeds is typically quite expensive. Seed costs will be substantially lower if field crops (sunflower,
mustard, alfalfa) are used to generate the microgreens. Determining the optimum seeding rates and
using production conditions that allow for maximum seed germination and optimum crop health will
also be important in crops where seed costs are high.
Labor Costs – it was estimated in trial #1 that it took about 15 minutes of labor to prepare, seed,
maintain and harvest each tray. At $12/h, labor would add about $3.00 to the cost of each tray.
Peppergrass grown in 406 cell peat trays (left) and on sure-to-grow pads (right).
Broccoli grown in 406 cell peat trays (left) and on “Sure-to-Grow” pads (right).
Ongoing trials
Continued testing of peat vs “Sure-to-Grow” pads as media for each crop.
Growing in low trays to facilitate harvest.
Germinating under light to speed growth and keep the stems short and stocky.
Adding nutrients to media at various growth stages.
Testing of radish, beets, daikon, peas, red clover, dill, broccoli, peppergrass, swiss chard, kohlrabi, red
cabbage, sunflower and other crops.
Hanging up “Sure-to-Grow” pads and using an electric knife to make harvesting quicker and easier.
Testing different methods as a means for removing seed coats.