Using the right amount of microgreen seed per tray is important for even germination, airflow, watering and harvest quality. Too little seed produces a sparse crop, while excessive density can trap moisture, restrict airflow and make the tray harder to manage.
There is no single seeding rate for every microgreen. A tray of broccoli may need only around 28g of seed, while the same tray can require more than 200g of field peas because pea seed is dramatically larger.
This guide compares current OzSprout seeding rates for broccoli, radish, mustard, pea shoots, pea tendrils and sunflower, explains how to scale the quantities for different tray sizes and shows how to adjust density without simply guessing.
Microgreen Seeding Rates per 25 × 50cm Tray
| Microgreen | Current OzSprout Seeding Rate | Pre-Soak |
|---|---|---|
| Broccoli Microgreen Seeds | Approx. 28g | None |
| Daikon Radish Microgreen Seeds | Approx. 22–28g | None |
| Purple Sango Radish Microgreen Seeds | Approx. 24–30g | None |
| Green Mustard Microgreen Seeds | Approx. 24–28g | None |
| Maple Pea Shoot Microgreen Seeds | Approx. 240–280g | 6–8 hours |
| Blue Pea Tendril Microgreen Seeds | Approx. 230–280g | 6–8 hours |
| Black Sunflower Microgreen Seeds | Approx. 100–140g | Approx. 8 hours |
These rates are for a tray with approximately 1,250cm² of growing area. If your tray is a different size, scale the seed quantity according to the surface area rather than using the same amount automatically.
Why Do Microgreen Seeding Rates Vary So Much?
Seed size is the most obvious reason, but it is not the only one.
The ideal seeding density can be influenced by:
- Seed size
- Seeds per gram
- Variety
- Seed lot
- Germination percentage
- Expected plant size
- Root development
- Desired stem thickness
- Growing medium
- Tray dimensions
- Harvest stage
Broccoli seed is small and can be sown densely while still requiring relatively little total weight. Peas are large and heavy, so considerably more grams are required to cover the same growing surface.
This is why using one instruction such as “two tablespoons per tray” for every microgreen is unreliable.
Always Measure Large Seeds Before Soaking
For crops such as peas and sunflower, the seeding rate refers to the dry seed weight before soaking.
Soaking changes the weight and volume of the seed because it absorbs water.
For repeatable results:
- Place an empty container on a kitchen scale.
- Tare the scale to zero.
- Measure the required amount of dry seed.
- Then soak the seed for the crop-specific period.
- Drain thoroughly before sowing.
Do not weigh soaked peas or sunflower and compare the result with a dry-seed specification.
Broccoli Microgreen Seeding Rate
Current OzSprout guidance is approximately 28g per 25 × 50cm tray.
Broccoli has relatively small seed and requires no pre-soaking.
Spread the 28g evenly across the growing surface rather than concentrating seed in thick patches.
Broccoli is relatively forgiving, but excessive density can still:
- Keep the growing surface unnecessarily wet
- Reduce airflow between seedlings
- Create uneven stem development
- Make harvesting more difficult
Aim for dense, even coverage without forming multiple layers of seed.
Daikon Radish Microgreen Seeding Rate
Current OzSprout guidance for Daikon is approximately 22–28g per 25 × 50cm tray.
Daikon does not require pre-soaking for microgreen production.
It germinates vigorously and expands rapidly, so there is little benefit in pushing the seed density far beyond the recommended range.
If using a new seed lot or growing system, start around the middle of the range and adjust after observing the finished canopy.
Purple Sango Radish Microgreen Seeding Rate
Current OzSprout guidance for Purple Sango is approximately 24–30g per 25 × 50cm tray.
Like Daikon, Purple Sango is sown dry for microgreen tray growing.
Its slightly different recommended density reflects the particular variety and seed characteristics rather than a rule that every radish should be sown at the same weight.
If you grow both varieties, see How to Grow Radish Microgreens at Home for the differences in blackout, harvest time and colour development.
Green Mustard Microgreen Seeding Rate
Current OzSprout guidance for Green Mustard is approximately 24–28g per 25 × 50cm tray.
Green Mustard has small seed and does not require pre-soaking.
Sow it evenly and avoid allowing seed to accumulate in dense piles. Mustard develops quickly, and an unnecessarily crowded canopy can make moisture and airflow more difficult to manage.
Maple Pea Shoot Seeding Rate
Current OzSprout guidance for Maple Brown Field Pea is approximately 240–280g of dry seed per 25 × 50cm tray.
Measure the seed before soaking, then soak for approximately 6–8 hours.
Peas need far more seed by weight because each individual seed is large. They also produce substantial roots and shoots, so simply packing more peas into the tray does not necessarily increase useful harvest.
An even layer with strong seed-to-medium contact is more important than maximum density.
For the complete growing method, see How to Grow Pea Shoots at Home.
Blue Pea Tendril Seeding Rate
Current OzSprout guidance for Blue Field Pea Tendrils is approximately 230–280g of dry seed per 25 × 50cm tray.
The seed should be measured before its 6–8 hour soak.
Blue Pea Tendrils are commonly grown slightly longer than Maple Pea Shoots so the curling tendrils can develop. This means the crop eventually produces a substantial canopy and root mass.
Do not assume that using more seed will automatically produce a better tray. Adequate root space, airflow and moisture control remain important.
Black Sunflower Microgreen Seeding Rate
Current OzSprout guidance for Black Sunflower is approximately 100–140g of dry seed per 25 × 50cm tray.
The formal current product specification uses an approximately 8-hour pre-soak.
After draining, spread sunflower seed as evenly as practical in approximately a single layer. The large seed benefits from good contact with the growing medium and light-to-moderate pressure during the early germination stage.
Sunflower is particularly sensitive to excessive crowding because the large hulls and fleshy seedlings create substantial organic material close to the growing surface.
For the complete crop method, see How to Grow Sunflower Microgreens at Home.
How Much Seed Should You Use in the OzSprout 33 × 28cm Grow Tray?
The OzSprout Microgreen & Wheatgrass Grow Tray – 33 × 28cm has a smaller surface area than the 25 × 50cm reference tray used in the current seed specifications.
A 25 × 50cm tray provides approximately 1,250cm² of growing area, while a 33 × 28cm tray provides approximately 924cm².
As a simple area-based starting point, the standard seed rates scale approximately as follows:
| Microgreen | 25 × 50cm Standard Rate | Approx. Starting Rate for 33 × 28cm Tray |
|---|---|---|
| Broccoli | 28g | Approx. 21g |
| Daikon Radish | 22–28g | Approx. 16–21g |
| Purple Sango Radish | 24–30g | Approx. 18–22g |
| Green Mustard | 24–28g | Approx. 18–21g |
| Maple Pea Shoot | 240–280g | Approx. 177–207g |
| Blue Pea Tendril | 230–280g | Approx. 170–207g |
| Black Sunflower | 100–140g | Approx. 74–103g |
These 33 × 28cm figures are area-scaled starting estimates, not replacements for the official 25 × 50cm product specifications.
Actual optimum density may still vary with seed size, germination performance, growing medium and the way you manage the crop.
How to Calculate Seed for Any Microgreen Tray Size
You can scale a known seeding rate using the surface area of the tray.
Step 1: Calculate the reference tray area:
25cm × 50cm = 1,250cm²
Step 2: Calculate the surface area of your tray:
Tray length × tray width = tray area
Step 3: Use this formula:
New seed amount = standard seed amount × new tray area ÷ 1,250
For a recommended range, calculate the lower and upper values separately.
This provides a sensible starting point. After growing a crop, record the amount you actually used and adjust slightly if necessary.
Why Weighing Microgreen Seed Is Better Than Using Tablespoons
Tablespoons are convenient, but weight is generally more consistent for tray growing.
A tablespoon of small broccoli seed bears little relationship to a tablespoon of large sunflower or pea seed.
Even within one crop:
- Seed size can vary between varieties.
- Individual seed lots can differ.
- How tightly a spoon is filled changes the volume measurement.
A simple digital kitchen scale makes it much easier to repeat a successful tray.
How to Spread Microgreen Seed Evenly
Correct total seed weight will not produce an even crop if the seed is distributed poorly.
After measuring:
- Prepare and level the growing medium.
- Divide the seed mentally into sections.
- Broadcast it gradually across the tray.
- Fill obvious bare patches.
- Break up thick clusters.
- Check the tray from several angles before covering.
For large crops such as pea and sunflower, aim for an even layer rather than deep piles of seed.
What Happens If You Use Too Much Microgreen Seed?
Over-seeding can cause:
- Poor airflow
- Trapped moisture
- Uneven germination
- Weak or stretched stems
- Greater competition between seedlings
- More difficult watering
- More seed hulls and organic material in the tray
- A greater chance of localised deterioration
A tray does not need every millimetre of visible surface completely hidden beneath multiple layers of seed.
Dense microgreen sowing and excessive seed crowding are not the same thing.
What Happens If You Use Too Little Seed?
An under-seeded tray may produce:
- A sparse canopy
- Lower harvest yield
- More visible gaps
- Uneven stem height
- Inefficient use of tray space
A sparse tray is not necessarily unhealthy, but it may not provide the yield or uniform appearance expected from microgreen production.
Should You Increase the Seed Rate When Germination Is Lower?
Only cautiously.
Germination percentage affects how many plants ultimately establish, but adding substantially more seed is not always the best solution.
If germination has fallen:
- Check seed storage.
- Check the age and current batch.
- Confirm the correct pre-soak method.
- Check moisture and temperature.
- Consider a small germination test.
Increasing density can compensate for a small difference in germination, but using excessive quantities of poorly performing seed can create a crowded layer of ungerminated seed that retains moisture and deteriorates.
Does Growing Medium Change the Seeding Rate?
The crop-specific rate is still a useful starting point, but the growing surface can influence how easily the seed establishes.
Consider:
- How flat the medium is
- How well it retains moisture
- Whether small seed can fall into large gaps
- How effectively large seed anchors
- How well the medium bottom waters
A fine, level surface makes it easier to achieve uniform density than a rough or uneven growing surface.
Should You Change Seeding Density for Hot Weather?
Do not make large density changes simply because the weather is warmer.
Instead, first adjust:
- Watering
- Airflow
- Growing position
- Light and heat exposure
Very dense crops can be harder to manage in warm, humid conditions, so avoid pushing seeding rates beyond the recommended range simply to maximise yield.
Does More Seed Always Mean More Microgreens?
No.
At first, increasing density may increase the number of seedlings in the tray. Beyond an appropriate point, however, the crop begins competing for the same space, water and airflow.
The objective is not to fit the maximum theoretical number of seeds into the tray. It is to produce the best usable crop from the available growing area.
Microgreen Seeding Density & Food Safety
Good seed density also helps make the crop easier to manage hygienically.
- Start with clean trays.
- Use drinking-quality water.
- Use clean growing medium appropriate for edible crops.
- Avoid excessive seed piles.
- Maintain drainage.
- Maintain airflow once the crop is uncovered.
- Remove clearly deteriorating or ungerminated large seeds where practical.
- Use clean harvest tools.
- Discard crops showing mould, slime, decay or abnormal odours.
Visible cleanliness cannot guarantee microbiological safety, so clean growing practices should be maintained throughout production.
Frequently Asked Questions About Microgreen Seeding Density
How much broccoli microgreen seed should I use per tray?
Current OzSprout guidance is approximately 28g per 25 × 50cm tray.
How much radish seed should I use per microgreen tray?
Current OzSprout guidance is approximately 22–28g for Daikon and 24–30g for Purple Sango per 25 × 50cm tray.
How much mustard microgreen seed per tray?
Current Green Mustard guidance is approximately 24–28g per 25 × 50cm tray.
How much pea seed should I use per tray?
Use approximately 240–280g of dry Maple Pea Shoot seed or 230–280g of dry Blue Pea Tendril seed per 25 × 50cm tray.
How much sunflower seed should I use?
Current Black Sunflower guidance is approximately 100–140g of dry seed per 25 × 50cm tray.
Should pea and sunflower seed be weighed before or after soaking?
Before soaking. The product seeding rates refer to dry seed weight.
How much broccoli seed should I use in the OzSprout 33 × 28cm grow tray?
Scaling the standard 28g rate by growing area gives an approximate starting quantity of 21g. Fine-tune this after observing your own crop.
Can I use the same seeding rate for every radish variety?
No. Current OzSprout guidance uses 22–28g for Daikon and 24–30g for Purple Sango. Use the specification for the actual variety being grown.
Is it better to over-seed or under-seed microgreens?
Neither. Start with the crop-specific recommended density. Slight under-seeding is generally easier to manage than creating thick piles of seed that restrict airflow and trap moisture.
How do I know if I used too much seed?
Signs can include seeds forming multiple layers, excessive crowding, trapped moisture, poor airflow and a very dense weak canopy.
Should I change the seeding rate if germination changes?
Minor adjustments can sometimes be useful, but first investigate seed storage, germination and growing conditions rather than automatically adding substantially more seed.
Microgreen Seeding Density: The Bottom Line
There is no universal amount of microgreen seed per tray.
For the current OzSprout varieties and a standard 25 × 50cm tray:
- Broccoli: approx. 28g
- Daikon Radish: approx. 22–28g
- Purple Sango Radish: approx. 24–30g
- Green Mustard: approx. 24–28g
- Maple Pea Shoot: approx. 240–280g
- Blue Pea Tendril: approx. 230–280g
- Black Sunflower: approx. 100–140g
Measure dry seed by weight, spread it evenly and treat the recommended range as the starting point. Record what works in your tray so future crops become repeatable rather than dependent on guesswork.
For additional varieties and their current crop-specific growing specifications, browse the OzSprout Microgreen Seeds range.