Mustard microgreens are fast-growing brassica microgreens with tender green leaves and a distinctive peppery, mustard-like flavour. They are relatively easy to grow indoors and can usually be harvested approximately 8–12 days after sowing.
If you’re wondering how to grow mustard microgreens, the process is straightforward. Mustard seeds do not normally require soaking and can be grown in shallow trays using soil, coco coir, seed-raising mix, hemp growing mats or another suitable microgreen growing medium.
This beginner-friendly guide explains how to grow mustard microgreens at home, including seed rate, germination, covered germination, watering, growing medium, light, temperature and when to harvest.
Mustard Microgreens at a Glance
What Are Mustard Microgreens?
Mustard microgreens are the young seedlings of mustard plants, commonly varieties of Brassica juncea. They belong to the Brassicaceae family alongside broccoli, kale, radish, cabbage, Mizuna and Tatsoi.
They are harvested when the seedlings are still young, normally once the cotyledons have fully opened and before substantial true-leaf development.
Depending on the variety, mustard microgreens may have green, red, purple or variegated foliage. Their flavour can range from moderately peppery to intensely spicy.
They are particularly useful for growers who want a fast crop with considerably more flavour than milder brassica microgreens such as broccoli.
What Do Mustard Microgreens Taste Like?
Mustard microgreens have a fresh, peppery and distinctly mustard-like flavour.
The flavour is usually stronger than broccoli, kale or Tatsoi microgreens and may produce a noticeable spicy sensation similar to mature mustard greens. Some varieties can also develop a horseradish or wasabi-like character.
Flavour intensity varies between mustard varieties and can also change with growing conditions and harvest stage.
The strong flavour works particularly well in salads, sandwiches, wraps, burgers, grain bowls and savoury garnishes where only a relatively small amount may be needed.
Why Grow Mustard Microgreens?
- Fast-growing microgreen with a short crop cycle.
- Usually ready to harvest in approximately 8–12 days.
- Distinctive peppery mustard flavour.
- No seed pre-soaking required.
- Small seed that is easy to distribute over a tray.
- Suitable for growing indoors throughout the year.
- Can be grown on soil, coco coir or suitable microgreen mats.
- Useful as a standalone crop or as the spicy component of a microgreen mix.
- Suitable for beginner and experienced microgreen growers.
Are Mustard Microgreens Easy to Grow?
Yes. Mustard is generally one of the easier microgreens to grow.
The seed is small, requires no pre-soaking and usually germinates quickly when supplied with consistent moisture and suitable temperatures.
Mustard also establishes rapidly once exposed to light.
The main challenge is avoiding an excessively dense or wet crop. Mustard seeds are small enough that it is easy to overseed the tray, which can restrict airflow and encourage mould or damping-off.
How to Grow Mustard Microgreens in 7 Simple Steps
- Prepare the growing tray. Add a shallow layer of moist growing medium and gently level the surface.
- Sow the mustard seeds. Spread approximately 10–15 g per 10 × 20 inch tray evenly across the surface.
- Mist thoroughly. Moisten the seeds and growing surface without washing the seed into clumps.
- Cover the tray. Use another tray or suitable cover during the initial germination period.
- Introduce light. Remove the cover once seedlings are established and pushing upward.
- Bottom water. Keep the root zone evenly moist while avoiding saturated growing media.
- Harvest. Cut the mustard microgreens just above the growing medium at approximately 8–12 days.
What You Need to Grow Mustard Microgreens
- Mustard microgreen seeds
- Shallow growing tray with drainage holes
- Solid bottom watering tray
- Second tray or suitable germination cover
- Soil, coco coir, seed-raising mix or suitable microgreen growing mat
- Spray mister
- Clean water
- Bright natural light or LED grow light
- Clean scissors or harvesting knife
Do Mustard Microgreen Seeds Need to Be Soaked?
No. Mustard microgreen seeds do not normally require soaking.
Unlike large seeds such as peas and sunflower, mustard seeds are small and absorb moisture readily once they are in contact with a damp growing medium.
Soaking may also make the small seeds more difficult to distribute evenly across the tray.
Sow the seeds dry and mist them thoroughly after planting.
How Much Mustard Seed Should You Use per Tray?
For a standard 10 × 20 inch microgreen tray, approximately 10–15 grams of mustard seed provides a practical starting rate.
For a 10 × 10 inch tray, use approximately 5–7.5 grams.
Exact sowing density can vary between mustard cultivars because seed size and growth habit are not identical.
More seed does not automatically produce a better crop. Mustard seedlings develop quickly, and excessive density can create a humid canopy with reduced airflow.
Spread the seed as evenly as possible and avoid leaving thick clumps or large overlapping piles.
Best Growing Medium for Mustard Microgreens
Mustard microgreens can be grown successfully using several growing media.
Seed-Raising Mix or Fine Potting Mix
A fine-textured seed-raising or quality potting mix provides a reliable medium for mustard microgreens.
Use approximately 2–4 cm of medium and level the surface before sowing.
Avoid very coarse mixes containing large pieces of bark because mustard seeds establish more evenly on a fine, level surface.
Coco Coir
Coco coir is another suitable option. It retains moisture well while providing a relatively clean and uniform growing surface.
Moisten the coir thoroughly before sowing but allow excess water to drain.
Microgreen Growing Mats
Mustard can also be grown on suitable hemp or other purpose-made microgreen growing mats.
The mat should remain evenly moist during establishment but should not sit continuously in deep water.
Best Temperature for Growing Mustard Microgreens
A practical indoor temperature range for mustard microgreens is approximately 18–24°C.
Mustard is a cool-season brassica and generally establishes well under mild conditions.
Very warm conditions can increase water use and disease pressure, particularly where trays are densely planted or ventilation is poor.
Consistent conditions are more important than maintaining an exact temperature.
Step 1: Prepare the Growing Tray
Start with clean trays and equipment.
If using soil, coir or seed-raising mix, add approximately 2–4 cm of growing medium to the tray.
Level the surface gently so seeds are not concentrated in depressions.
Moisten the growing medium before sowing. It should be evenly damp without being saturated.
Step 2: Sow the Mustard Seeds
Spread the mustard seeds evenly over the growing medium.
For a standard 10 × 20 inch tray, start with approximately 10–15 g of seed.
The seeds can sit on or very close to the surface. A heavy covering of soil is unnecessary.
Gently press the seeds against the growing medium to improve seed-to-medium contact.
Mist thoroughly after sowing.
Step 3: Cover the Tray During Germination
Place another tray or suitable cover over the freshly sown seeds.
This helps retain moisture and provides darkness during initial germination.
Check the crop regularly and mist the growing surface if necessary.
Mustard commonly germinates within approximately 3–7 days, although initial germination can begin sooner under favourable conditions.
Do Mustard Microgreens Need Weight?
Heavy weighting is generally not necessary for mustard microgreens.
A second tray can provide light, even contact during early germination, but mustard does not require the substantial weighting sometimes used for crops such as sunflower or pea shoots.
The purpose of the covering tray is mainly to maintain moisture, darkness and good contact with the growing surface.
How Long Should Mustard Microgreens Stay Covered?
Around 2–3 days of covered germination provides a useful starting point.
However, crop development is a better guide than the calendar.
Remove the cover when the majority of seeds have germinated and the young seedlings are established and beginning to push upward.
Avoid keeping mustard in prolonged darkness simply to produce taller stems. Excessive stretching can weaken the crop.
Step 4: Move the Mustard Microgreens into Light
Once the seedlings are established, remove the cover and move the tray into bright natural light or beneath a suitable grow light.
Seedlings may initially appear pale or yellow when uncovered. This is normal after germination in darkness.
The cotyledons should become green or develop their characteristic cultivar colour after exposure to light.
Good light helps produce compact, sturdy seedlings rather than excessively elongated stems.
Step 5: Water Mustard Microgreens Carefully
Keep the growing medium consistently moist while the crop develops, but avoid continuous saturation.
Once roots are established, bottom watering is generally preferable to repeatedly wetting the foliage.
Add water to the solid lower tray and allow moisture to move upward through the drainage holes.
Check the crop before watering again rather than following a rigid daily quantity.
- Keep the root zone moist
- Avoid waterlogged growing media
- Do not leave unnecessary standing water beneath trays
- Reduce overhead watering once foliage develops
- Maintain airflow around the crop
Step 6: Allow the Cotyledons to Develop
Once exposed to light, mustard microgreens grow rapidly.
The cotyledons expand and the canopy becomes increasingly dense as the plants approach harvest.
Maintain good light, adequate airflow and even moisture.
Depending on the cultivar, the foliage may be green, red, purple or mixed in colour.
Step 7: When to Harvest Mustard Microgreens
Mustard microgreens are generally ready for harvest approximately 8–12 days after sowing.
Rather than relying exclusively on the number of days, examine the crop.
Look for:
- Fully opened cotyledons
- Healthy upright stems
- Plants approximately 5–8 cm tall
- Good cultivar colour
- Tender stems and leaves
- Little or early true-leaf development
You can taste a small sample as the crop develops. Mustard flavour can become quite pronounced, so the ideal harvest stage partly depends on your preferred flavour intensity.
How to Harvest Mustard Microgreens
Harvest with clean scissors or a sharp harvesting knife.
Cut the stems just above the growing medium.
Try to avoid cutting soil, coir or pieces of growing mat into the harvested crop.
Where possible, harvest when the foliage is reasonably dry rather than immediately after overhead watering.
Mustard is generally treated as a single-cut microgreen crop. Sow a fresh tray for your next harvest.
How Much Can You Harvest from a Tray?
Mustard microgreen yield varies according to cultivar, seed density, germination percentage, growing medium, temperature, light and harvest stage.
Research into Indian mustard microgreen production has also demonstrated that sowing density influences crop yield, reinforcing the importance of using an appropriate seed rate rather than simply adding as much seed as possible.
For home growers, a uniform and well-ventilated stand of seedlings is generally preferable to an excessively dense crop.
Research into Mustard Microgreens
Mustard microgreens have been used in scientific studies examining microgreen production, light, storage and naturally occurring plant compounds.
For example, research published in the scientific literature has examined Brassica juncea mustard microgreens grown under different light intensities.
Other research has investigated seed density and harvest timing in Indian mustard microgreens, with results showing that production characteristics can vary according to growing method and crop management.
These studies are useful for understanding the crop, but growing conditions used in controlled research are not necessarily identical to those in a home microgreen setup.
Mustard Microgreens vs Broccoli Microgreens
Mustard and broccoli are both brassica microgreens and have similar basic growing requirements, but they differ noticeably in flavour.
Mustard Microgreens vs Radish Microgreens
Mustard and radish are both fast-growing, peppery microgreens, but their flavour and crop characteristics are not identical.
Mustard Microgreens vs Mustard Baby Greens
Mustard microgreens and baby mustard greens come from the same type of plant but are grown at different densities and harvested at different stages.
Growing Mustard Microgreens in Warm and Humid Weather
Mustard is a cool-season brassica, so trays require additional attention during hot and humid Australian conditions.
Warmth, dense growth and prolonged moisture around the stems can increase the likelihood of crop problems.
During warm weather:
- Maintain good airflow around trays
- Avoid excessive sowing density
- Do not keep trays saturated
- Bottom water once roots are established
- Avoid leaving standing water beneath the tray
- Move seedlings out of blackout promptly once established
- Avoid intense afternoon heat through a window
- Use a small fan where indoor air is stagnant
In humid subtropical areas such as Brisbane, airflow becomes particularly important because dense microgreen canopies can remain damp for longer than they do in cooler or drier climates.
Common Problems When Growing Mustard Microgreens
Mould
Mould is more likely where mustard is sown too densely, overwatered or grown with poor ventilation.
To reduce the risk:
- Start with clean trays and equipment
- Use an appropriate seed density
- Keep the growing medium moist rather than saturated
- Provide good drainage
- Maintain airflow
- Remove the cover once germination is established
Discard visibly mouldy or spoiled microgreens rather than eating them.
White Fuzz Around the Roots
Fine white hairs around young mustard roots are often root hairs rather than mould.
Root hairs normally appear evenly around healthy roots and may become difficult to see immediately after misting.
Mould tends to spread less uniformly across seed, stems or growing medium.
Yellow Mustard Seedlings After Blackout
Pale or yellow seedlings are normal immediately after a period of dark germination.
Once exposed to suitable light, the seedlings should begin developing their normal green, red or purple colouring.
Leggy Mustard Microgreens
Excessively tall, weak seedlings often indicate insufficient light or too much time spent under the germination cover.
Move established seedlings into suitable light and avoid unnecessarily extending the blackout period.
Mustard Seedlings Are Falling Over
Check the crop for excessive density, insufficient light, overwatering or poor airflow.
Weak seedlings may also develop where temperatures are high and the crop remains too moist.
Mustard Microgreens Are Wilting
Wilting commonly indicates that the root zone has become too dry.
Check moisture levels more frequently in warm weather or under strong grow lighting.
If the growing medium is already saturated and the crop is collapsing, inspect the seedlings for disease or poor drainage rather than adding more water.
Frequently Asked Questions
How long do mustard microgreens take to grow?
Mustard microgreens are commonly ready to harvest approximately 8–12 days after sowing. Growth rate varies with cultivar, temperature, light, moisture and growing conditions.
Do mustard microgreen seeds need to be soaked?
No. Mustard seeds do not normally need to be pre-soaked before sowing.
How much mustard seed should I use in a 10 × 20 tray?
Approximately 10–15 grams provides a useful starting sowing rate for a standard 10 × 20 inch microgreen tray.
How much mustard seed should I use in a 10 × 10 tray?
Approximately 5–7.5 grams is a practical starting rate for a 10 × 10 inch tray.
How long should mustard microgreens stay covered?
Approximately 2–3 days is a useful starting point. Uncover the crop once most seeds have germinated and the seedlings are established and pushing upward.
Do mustard microgreens need blackout?
A short period of covered or dark germination is commonly used to help establish an even crop. Once the seedlings are established, remove the cover and introduce suitable light.
Do mustard microgreens need weight?
Heavy weighting is not generally required. A covering tray can provide light contact during initial germination.
Can mustard microgreens be grown without soil?
Yes. Mustard can be grown using suitable soilless media such as coco coir or purpose-made microgreen growing mats.
Do mustard microgreens need light?
The seed does not require light during initial germination. After the covered germination period, the developing seedlings need suitable natural or artificial light to produce healthy coloured foliage.
What temperature is best for mustard microgreens?
Approximately 18–24°C provides a useful indoor growing range.
When should mustard microgreens be harvested?
Harvest when the cotyledons are fully opened, stems are tender and the plants have reached approximately 5–8 cm in height. This commonly occurs around 8–12 days after sowing.
What do mustard microgreens taste like?
Mustard microgreens have a distinctive peppery, spicy mustard flavour. The intensity varies considerably between cultivars.
Are mustard microgreens hotter than broccoli microgreens?
Generally, yes. Mustard microgreens normally have a stronger and more pungent flavour than the relatively mild flavour of broccoli microgreens.
Can mustard microgreens be grown indoors?
Yes. Mustard is well suited to indoor production using a bright windowsill or suitable grow lights, provided the crop also receives adequate ventilation.
Do mustard microgreens regrow after harvest?
Mustard is generally grown as a single-cut crop. Sow a new tray for the next harvest.
Final Tips for Growing Mustard Microgreens
Learning how to grow mustard microgreens is straightforward, making mustard a useful crop for beginner and experienced growers who enjoy stronger-flavoured microgreens.
The seeds do not normally require soaking, establish quickly and can usually be harvested approximately 8–12 days after sowing.
For the best results, sow the seed evenly, avoid overcrowding, maintain consistent moisture during germination, introduce good light once the seedlings are established and provide adequate airflow throughout the crop.
With a clean tray, suitable growing medium and careful watering, mustard can produce a fast crop of tender microgreens with a distinctive peppery flavour.
Ready to grow your own? Shop Mustard Microgreen Seeds from Seedmart Australia.