How much microgreen seed should you use per tray? There is no single rate that works for every crop or every tray.
Microgreen seed density depends on the crop, seed size, variety, seed lot, germination percentage, tray dimensions and the type of crop you want to produce.
This can be particularly confusing for Australian growers because many growing guides use the American 10 × 20 inch, or 1020, tray as their reference. Australian growers also use 30 × 35 cm propagation trays, compact 1010 trays, shallow Australian commercial trays and a variety of smaller home-growing trays.
This guide brings those formats together and gives practical starting seeding ranges rather than pretending there is one exact number for every grower.
How to Use These Seed Rates
The figures in this guide have been reviewed against current commercial microgreen growing references.
Rates for 1020 trays are published reference ranges. Rates for other tray sizes are approximate conversions based on tray area unless otherwise stated.
Use them as starting points. Your best final rate may be slightly higher or lower depending on your seed and growing system.
Why have some Seedmart rates changed? Earlier Seedmart growing information used approximately 28 g per 1020 tray for a large number of small-seeded crops. Current crop-specific growing data shows that this was too broad. Broccoli, mustard, kale, basil and other crops should not all be treated as having the same ideal density.
Quick Guide: 30 × 35 cm Tray
For a nominal 30 × 35 cm tray, practical starting ranges are approximately:
- Broccoli: 12–16 g
- Kale: 12–16 g
- Mustard / Mizuna: 8–12 g
- Radish: 23–28 g
- Peas: 165–225 g dry seed
- Black sunflower: 120–140 g dry seed
- Beetroot: 16–24 g
- Silverbeet / Chard: 16–26 g
In This Guide
Microgreen Tray Sizes Used in Australia
There is no single standard tray used by every Australian microgreen grower.
30 × 35 cm Australian Growing Tray
Outer dimensions: approximately 30 × 35 cm
This is Seedmart’s standard propagation-tray format and is commonly used in Australia for seedlings, microgreens, wheatgrass and similar crops.
It is deeper than most specialist microgreen trays. Microgreens generally do not require the tray to be filled to its full depth with growing medium.
The 30 × 35 cm measurements give a nominal rectangular area of 1,050 cm², but the true internal growing area will usually be smaller because of the tray walls and taper.
1010 Microgreen Tray
Nominal size: approximately 10 × 10 inches
The 1010 is a compact specialist microgreen tray. It is useful for home growers, smaller harvests and variety trials.
Two nominal 1010 growing areas equal approximately one nominal 1020 area, although actual internal dimensions vary between manufacturers.
1020 Microgreen Tray
Nominal size: approximately 10 × 20 inches
The 1020 is the most widely referenced tray in North American microgreen growing information and is commonly used by commercial growers.
Because so much crop-specific growing data is published for 1020 trays, this guide uses it as the main reference for comparing seeding density.
Curly’s Ag Australian Commercial Microgreen Tray
Outer dimensions: approximately 58.8 × 31.2 cm
Published internal dimensions: approximately 55.7 × 27.8 cm
This is a shallow Australian-made commercial format with a larger growing surface than the standard Seedmart propagation tray.
For calculations in this guide we use the published internal dimensions rather than the outside dimensions.
Small Home Microgreen Trays
Amazon and other marketplaces sell many smaller propagation and microgreen trays.
For comparison, this guide includes an example tray of approximately 32.8 × 25 cm. This is not an industry-standard size.
For any unlisted tray, measuring your own internal growing surface will give a better conversion.
Do not worry if you cannot measure the exact internal dimensions. Using the nominal dimensions gives a useful starting estimate. Seeding-density recommendations themselves vary enough between seed lots and growing systems that a few centimetres of tray-wall difference does not justify false precision.
Microgreen Seeding Density Chart for Australian Tray Sizes
The 1020 column below shows the reviewed reference range used for conversion. The other columns are approximate area-based equivalents.
Figures have deliberately been rounded to practical amounts rather than presented to decimal-point precision.
| Microgreen | 30 × 35 cm Approx. |
1010 Approx. |
1020 Reference |
Curly’s Ag Approx. |
Small Home Tray Approx. |
|---|---|---|---|---|---|
| Amaranth | 12–16 g | 8–10 g | 15–20 g | 18–24 g | 10–13 g |
| Basil | 6–8 g | 4–5 g | 8–10 g | 10–12 g | 5–6 g |
| Beetroot | 16–24 g | 10–15 g | 20–30 g | 24–36 g | 13–19 g |
| Broccoli | 12–16 g | 8–10 g | 15–20 g | 18–24 g | 10–13 g |
| Coriander / Cilantro | 20–28 g | 12–18 g | 25–35 g | 30–42 g | 16–22 g |
| Kale | 12–16 g | 8–10 g | 15–20 g | 18–24 g | 10–13 g |
| Kohlrabi | 12–16 g | 8–10 g | 15–20 g | 18–24 g | 10–13 g |
| Mustard / Mizuna | 8–12 g | 5–8 g | 10–15 g | 12–18 g | 6–10 g |
| Parsley | 12–16 g | 8–10 g | 15–20 g | 18–24 g | 10–13 g |
| Pea Shoots | 165–225 g | 100–140 g | 200–275 g | 240–330 g | 125–175 g |
| Radish | 23–28 g | 14–18 g | 28–35 g | 34–42 g | 18–22 g |
| Rocket / Arugula | 8–10 g | 5–6 g | 10–12 g | 12–14 g | 6–8 g |
| Silverbeet / Chard | 16–26 g | 10–16 g | 20–32 g | 24–38 g | 13–20 g |
| Shiso / Perilla | 10–12 g | 6–8 g | 12–15 g | 14–18 g | 8–10 g |
| Red-Veined Sorrel | ~2.5 g | ~1.5 g | ~3 g | ~3.5–4 g | ~2 g |
| Black Sunflower | 120–140 g | 75–85 g | 150–170 g | 180–205 g | 95–110 g |
Why ranges rather than exact numbers? A 15 g recommendation and a 20 g recommendation can both be appropriate for the same crop. Seed size, variety, germination percentage, harvest stage and desired canopy density all affect how much seed is appropriate.
How to Calculate Microgreen Seed for Another Tray Size
You can convert a known seeding rate according to tray growing area.
New seed rate = known seed rate × new tray area ÷ known tray area
Example: Broccoli
A nominal 1020 tray measures approximately 10 × 20 inches, or 25.4 × 50.8 cm.
Its nominal area is therefore approximately 1,290 cm².
A 30 × 35 cm rectangle has a nominal area of 1,050 cm².
The nominal 30 × 35 cm tray therefore represents about 81% of the area of a nominal 1020.
If the starting broccoli range is 15–20 g per 1020:
15–20 g × approximately 0.81 = approximately 12–16 g
This is why the chart recommends around 12–16 g of broccoli seed as a starting range for the 30 × 35 cm tray.
Why This Is Only an Estimate
Tray sides are rarely perfectly vertical. A nominal 30 × 35 cm tray may therefore have less than 1,050 cm² of usable growing surface.
That does not make the conversion useless. It simply means that the calculated rate should be treated as a starting point rather than a laboratory specification.
How Much Broccoli Microgreen Seed Per Tray?
Broccoli is a small-seeded brassica. Current commercial references generally use less seed than Seedmart’s earlier 28 g-per-1020 figure.
| Tray | Broccoli Starting Range |
|---|---|
| 30 × 35 cm | 12–16 g |
| 1010 | 8–10 g |
| 1020 | 15–20 g |
| Curly’s Ag commercial tray | 18–24 g |
Broccoli seed should form a dense but even layer. Avoid deliberately creating multiple layers of seed to increase yield.
How Much Radish Microgreen Seed Per Tray?
Radish has larger seed than broccoli, kale and mustard, so its seeding rate is correspondingly higher.
A practical current 1020 starting range is approximately 28–35 g, depending on variety and seed size.
| Tray | Radish Starting Range |
|---|---|
| 30 × 35 cm | 23–28 g |
| 1010 | 14–18 g |
| 1020 | 28–35 g |
| Curly’s Ag commercial tray | 34–42 g |
Daikon, purple radish and other varieties may not require exactly the same weight because seed size differs.
How Much Pea Seed Per Microgreen Tray?
Peas require far more seed by weight than brassicas because individual pea seeds are large and heavy.
After reviewing current commercial growing references, Seedmart’s former 100 g per 30 × 35 cm starting rate appears light for a densely grown tray.
A better general starting range is approximately 165–225 g of dry pea seed per nominal 30 × 35 cm tray.
| Tray | Dry Pea Seed |
|---|---|
| 30 × 35 cm | 165–225 g |
| 1010 | 100–140 g |
| 1020 | 200–275 g |
| Curly’s Ag commercial tray | 240–330 g |
Always weigh peas dry. Peas absorb substantial water during soaking, so weighing soaked seed makes density difficult to reproduce.
Different field pea, snow pea and tendril varieties can vary considerably in individual seed size. Adjust the rate if your seed lot is noticeably larger or smaller.
How Much Sunflower Seed Per Microgreen Tray?
Sunflower was the largest correction in Seedmart’s earlier density information.
The previous recommendation of 200–250 g per 30 × 35 cm tray is heavier than necessary as a general starting rate.
Published recommendations for black-oil sunflower vary considerably between growers, but a practical Seedmart starting range for a nominal 30 × 35 cm tray is approximately 120–140 g of dry seed.
| Tray | Dry Black Sunflower Seed |
|---|---|
| 30 × 35 cm | 120–140 g |
| 1010 | 75–85 g |
| 1020 | 150–170 g |
| Curly’s Ag commercial tray | 180–205 g |
Sunflower rates vary more than most crops. Published 1020 recommendations range from roughly 120 g to 250 g. Seed size, cultivar, germination method and desired density explain much of this variation. Start around 120–140 g in the Seedmart tray and adjust after observing your own crop.
Weigh sunflower seed before soaking.
Small-Seeded Microgreens: Kale, Mustard, Mizuna and Kohlrabi
One of the main findings from reviewing Seedmart’s older density information is that small seed does not automatically mean 28 g per 1020 tray.
Current starting ranges are generally lower.
| Crop | 30 × 35 cm | 1020 Reference |
|---|---|---|
| Kale | 12–16 g | 15–20 g |
| Kohlrabi | 12–16 g | 15–20 g |
| Mustard | 8–12 g | 10–15 g |
| Mizuna | 8–12 g | 10–15 g |
| Rocket / Arugula | 8–10 g | 10–12 g |
With fine seed, even distribution is particularly important. A small concentrated patch can contain many seedlings and become overcrowded even when the rest of the tray is correctly seeded.
How to Spread Microgreen Seed Evenly
1. Level the Growing Medium
A level surface makes consistent seed distribution much easier.
2. Weigh the Seed
Use a small digital scale. Weight is much more repeatable than tablespoons, cups or handfuls.
3. Sow in Several Passes
Scatter part of the measured seed across the whole tray, then repeat. This is easier than trying to place the entire amount evenly in one movement.
4. Check the Edges
Seed is often concentrated in the middle while the corners and outside edges remain sparse.
5. Remove Obvious Piles
Seed should be densely and evenly distributed rather than sitting in deep piles.
How Much Microgreen Seed Should I Buy?
Once you establish your own rate, estimating seed requirements becomes straightforward.
Number of trays = total seed weight ÷ seed used per tray
Broccoli: Based on Approximately 12–16 g per 30 × 35 cm Tray
| Seed Quantity | Approximate Number of Trays |
|---|---|
| 100 g | About 6–8 trays |
| 250 g | About 15–20 trays |
| 1 kg | About 62–83 trays |
| 5 kg | About 310–415 trays |
Peas: Based on Approximately 165–225 g per 30 × 35 cm Tray
| Seed Quantity | Approximate Number of Trays |
|---|---|
| 1 kg | About 4–6 trays |
| 5 kg | About 22–30 trays |
| 20 kg | About 89–121 trays |
Sunflower: Based on Approximately 120–140 g per 30 × 35 cm Tray
| Seed Quantity | Approximate Number of Trays |
|---|---|
| 1 kg | About 7–8 trays |
| 5 kg | About 35–42 trays |
| 20 kg | About 142–166 trays |
Commercial growers: Seed cost per tray is often more useful than price per kilogram. A cheaper seed that requires substantially more grams per tray is not necessarily the lower-cost crop.
Can You Put Too Much Microgreen Seed in a Tray?
Yes. Microgreens are grown densely, but increasing seed indefinitely does not produce an indefinitely heavier crop.
Too much seed can contribute to:
- Poor airflow
- Overlapping layers of seed
- Uneven germination
- Moisture becoming trapped around stems and hulls
- Greater competition between seedlings
- Dense root mats
- More difficult watering
- Weak or elongated plants
- More difficult harvesting
This is one reason Seedmart has reduced several earlier recommendations. Using more seed than necessary increases seed cost and can make the tray harder to manage without delivering a proportional increase in usable harvest.
What Happens If You Don’t Use Enough Seed?
Underseeding is generally easier to manage than severe overcrowding, but it can produce:
- A sparse canopy
- Lower harvest weight per tray
- Unused growing area
- Large spaces between seedlings
- Uneven stem height
If the crop is healthy but visibly sparse, increase the rate gradually on your next tray.
Should You Add More Seed to Compensate for Poor Germination?
Usually not until you understand why germination is low.
A low-germination seed lot can leave large quantities of wet, ungerminated seed inside a densely planted tray. Simply adding more seed can therefore make the crop harder to manage.
First review seed storage, seed age, soaking requirements, temperature, moisture, seed-to-medium contact and germination conditions.
If the seed is healthy but its germination percentage is consistently below that of another lot, a modest density adjustment may then be appropriate.
Why Seed Weight Changes Between Varieties
Two varieties of the same crop can require different weights per tray because the individual seeds may be different sizes.
This is especially noticeable with:
- Peas
- Sunflower
- Radish
- Beetroot and chard
- Coriander
A gram of very small seed contains more individual seeds than a gram of large seed.
This is why seeding density should ultimately be judged by both weight and the resulting physical coverage of the tray.
Does the Growing Medium Affect Seeding Density?
The starting seed weight does not necessarily change simply because you switch growing medium, but the quality of establishment can change.
A fine, level seed-raising mix or coir surface makes it easier to spread fine seed evenly. Coarse material can allow small seed to drop into gaps.
When comparing growing media, look at surface evenness, moisture retention, drainage, root anchoring and bottom-watering performance.
If you are refining a commercial growing system, avoid changing both the medium and seed rate at the same time. Change one variable and record the result.
Does Australian Weather Affect Microgreen Seeding Density?
Temperature and humidity do not necessarily require a completely different seed rate, but they change how easily a dense crop can be managed.
In hot or humid Australian conditions, dense trays can retain moisture around stems, seed hulls and the growing medium for longer.
Before changing the seed rate substantially, review:
- Watering
- Air circulation
- Tray spacing
- Humidity
- Growing location
- Excess direct sunlight or radiant heat
Hot-weather tip: Do not increase seed density simply to chase a heavier yield in warm, humid weather. A slightly more open crop may be easier to water and ventilate.
How to Fine-Tune Your Own Microgreen Seeding Rate
The best long-term source of information is your own growing record.
For each crop, record:
- Crop and variety
- Seed lot
- Dry seed weight
- Tray type
- Internal growing dimensions if known
- Growing medium
- Germination result
- Stacking or blackout period
- Harvest day
- Harvest weight
- Any watering, mould or airflow problems
Make small changes. If 14 g of broccoli gives you a healthy but slightly sparse crop, try 15 or 16 g next time rather than jumping to 25 g.
Likewise, if 140 g of sunflower is obviously overcrowded, try 125–130 g on the next tray.
For commercial growers, the most profitable rate is not necessarily the highest possible seeding rate. The aim is reliable marketable yield for the lowest practical combination of seed, medium, labour and crop loss.
More Microgreen Growing Guides
Seedmart’s complete Australian microgreen growing guide.
How to Grow Broccoli Microgreens
Step-by-step broccoli growing guide for home growers.
How to Grow Radish Microgreens
Growing radish microgreens from sowing to harvest.
Soaking, germinating and growing pea shoots.
How to Grow Sunflower Microgreens
Growing black sunflower microgreens from dry seed to harvest.
Frequently Asked Questions About Microgreen Seeding Density
How much seed should I use in a 30 × 35 cm microgreen tray?
It depends on the crop. Approximate starting rates include 12–16 g for broccoli, 8–12 g for mustard or mizuna, 23–28 g for radish, 165–225 g for peas and 120–140 g for black sunflower.
Why has Seedmart changed some of its old microgreen seed rates?
Seedmart’s earlier information used approximately 28 g per 1020 tray for many different small-seeded varieties. A review of current crop-specific growing data showed that this was too general. Different crops require substantially different densities.
How much broccoli seed should I use?
Approximately 15–20 g per 1020 tray is a useful current reference range. That converts to roughly 12–16 g for a nominal 30 × 35 cm tray.
How much radish seed should I use?
A useful starting range is approximately 28–35 g per 1020 tray, or about 23–28 g for a nominal 30 × 35 cm tray.
How much pea seed should I use?
Approximately 200–275 g of dry pea seed per 1020 is a common commercial starting range. For a nominal 30 × 35 cm tray, this converts to approximately 165–225 g.
How much sunflower seed should I use?
Sunflower recommendations vary considerably. Seedmart now suggests approximately 120–140 g of dry black sunflower seed per nominal 30 × 35 cm tray as a practical starting range.
Was 200–250 g of sunflower seed per 30 × 35 cm tray too much?
As a general recommendation, yes. That rate is at the very dense end of published sunflower growing systems. A starting range around 120–140 g is more appropriate, with adjustment according to seed size and crop performance.
Should pea and sunflower seed be weighed before or after soaking?
Before soaking. Both crops absorb substantial quantities of water, so dry weight provides the consistent reference.
What is a 1020 microgreen tray?
A 1020 is nominally about 10 × 20 inches. It is commonly used by commercial microgreen growers and is the standard reference size in much North American growing information.
What is a 1010 tray?
A 1010 is nominally about 10 × 10 inches and has approximately half the growing area of a nominal 1020 tray.
Do all 1020 trays have exactly the same internal dimensions?
No. The name describes a general tray format rather than an exact internal growing measurement. Wall thickness, taper and manufacturer design can change the actual sowing area.
Do I need exact internal tray measurements?
No. Exact measurements improve area conversions, but density recommendations themselves are starting points. Using nominal tray dimensions is usually sufficient for establishing an initial rate.
Should I measure microgreen seed in grams or tablespoons?
Grams are more repeatable because seed size, shape and packing density vary between crops and seed lots.
Is more seed better?
No. Excessive density can reduce airflow, trap moisture, increase competition and increase seed cost without producing a proportional increase in usable harvest.
Why do different growers recommend different seed rates?
They may use different varieties, seed lots, tray designs, harvest stages, growing media, germination systems and target crop densities. A range is therefore often more useful than one supposedly exact number.
Microgreen Seeds for Home and Commercial Growers
Seedmart Australia supplies microgreen seed in packet and bulk quantities for home growers, market gardeners and commercial microgreen production.
Choose your crop, establish a repeatable seeding rate for your trays, then calculate the amount of seed you need.
Download the Seedmart Microgreen Growing Guide
Download our general microgreen growing guide for additional crop and growing information.