Nasturtium Microgreen Seeds

Nasturtium is a distinctive specialty microgreen with broad rounded leaves, substantial stems and a strong peppery flavour. Its large seeds benefit from a short pre-soak and require more space than small-seeded crops such as broccoli or mustard.

What You Need

• Nasturtium Microgreen Seeds
• A shallow tray with drainage holes
• A solid lower tray for bottom watering
• Coco coir, fine seed-raising mix or another well-drained microgreen medium
• Optional fine vermiculite
• A clean soaking container
• Clean drinking-quality water
• A second tray or suitable blackout cover
• Bright natural light or suitable grow lights
• Clean scissors or a sharp harvesting knife

Seed Rate

For a standard 25 × 50cm microgreen tray, use approximately:

120–135g dry Nasturtium seed per tray

Measure the seed before soaking.

After soaking, distribute the swollen seeds evenly with minimal overlap.

Do not create thick piles of seed. The large hydrated seeds retain considerable moisture, and excessive overlap can create humid pockets and uneven growth.

Pre-Soak

Pre-soak for approximately:

2–4 hours

1. Measure the required dry seed.
2. Rinse thoroughly with clean drinking-quality water.
3. Place the seed in a clean container.
4. Cover generously with cool to lukewarm water.
5. Soak for approximately 2–4 hours.
6. Drain thoroughly before sowing.

Complete drainage after soaking is important.

Step-by-Step Instructions

1. Clean your equipment. Wash and thoroughly rinse the trays, soaking container, cover and growing tools.
2. Prepare the growing medium. Add approximately 2–3cm of coco coir, fine seed-raising mix or another suitable well-drained medium.
3. Moisten before sowing. Water evenly and allow excess water to drain. The medium should be thoroughly damp without being waterlogged.
4. Soak the seed. Soak for approximately 2–4 hours, then drain thoroughly.
5. Sow evenly. Spread the seeds across the tray with as little overlap as practical.
6. Press gently. Ensure good contact between the seed and growing medium.
7. Cover lightly if preferred. A thin layer of fine growing medium or vermiculite can help retain moisture around the large seeds.
8. Mist lightly if required. Avoid saturating the seed layer.
9. Cover the tray. Use another tray or suitable opaque cover during early germination.
10. Check daily. Maintain consistent moisture without keeping the seeds permanently wet.
11. Uncover once established. Remove the cover when most seedlings have rooted and are pushing upward.
12. Provide light and airflow. Move the crop into bright indirect natural light or beneath suitable grow lights.
13. Bottom water once rooted. Switch primarily to watering from below as the root system establishes.

Blackout

Keep the tray covered for approximately:

3–4 days

Heavy weighting is generally unnecessary.

Use the crop rather than the calendar alone as your guide. Remove the cover once the majority of seedlings are rooted and beginning to push upward.

For more information about covered germination, see Microgreen Blackout Explained.

Germination

Expect germination in approximately:

4–7 days

Nasturtium is slower to establish than many small-seeded brassica microgreens.

Some variation between individual seeds is normal.

Maintain steady moisture without leaving the large seeds continually saturated.

Temperature

Aim for approximately:

18–24°C

Moderate indoor temperatures support steady germination and growth.

Avoid excessive heat combined with high humidity, particularly while the large seeds are still covered and establishing.

Light

Once uncovered:

• provide bright indirect natural light or suitable grow lights;
• maintain good airflow;
• rotate the tray if required for even growth;
• avoid excessive heat; and
• minimise prolonged moisture on the broad leaves.

Good light encourages sturdy stems and healthy rounded foliage.

Watering

During early establishment, water conservatively.

The large soaked seeds retain considerable moisture, so unnecessary watering can keep the seed layer excessively wet.

Once roots are established, bottom watering is preferable.

For more detail, see How to Water Microgreens: Misting vs Bottom Watering.

When bottom watering:

• add a shallow amount of water to the lower tray;
• allow the growing medium to absorb moisture;
• check the medium before watering again;
• do not leave standing water beneath the tray;
• minimise repeated wetting of the broad foliage; and
• maintain good airflow.

Tips for Best Results

• Use approximately 120–135g per 25 × 50cm tray.
• Pre-soak for approximately 2–4 hours.
• Drain thoroughly before sowing.
• Avoid excessive seed overlap.
• Use a well-drained growing medium.
• A light vermiculite covering can help maintain even moisture.
• Blackout for approximately 3–4 days.
• Expect germination in approximately 4–7 days.
• Maintain approximately 18–24°C.
• Provide bright light after uncovering.
• Maintain good airflow.
• Bottom water once established.
• Harvest at approximately 14–21 days.

Avoid Excessive Seed Overlap

Nasturtium seeds expand after soaking.

The recommended seed rate should still be distributed as evenly as possible rather than creating multiple layers of swollen seed.

Excessive overlap can:

• reduce airflow;
• produce uneven rooting;
• retain excess moisture; and
• increase the likelihood of seed deterioration.

Light Surface Covering

A thin layer of fine growing medium or vermiculite can be useful after sowing.

This can help:

• maintain moisture around the seed;
• improve contact with the growing surface;
• support more even rooting; and
• prevent exposed seeds from drying too quickly.

Do not bury the seeds deeply.

Root Hairs vs Mould

Fine white root hairs can sometimes be mistaken for mould.

Healthy root hairs generally:

• emerge directly from individual roots;
• appear relatively evenly;
• become more visible as roots dry slightly; and
• become less noticeable immediately after watering.

Mould is more likely to:

• spread irregularly between seeds;
• form web-like patches;
• persist after watering; or
• occur with slime, seed breakdown or unpleasant odours.

If you are uncertain, see Mould vs Root Hairs on Sprouts & Microgreens.

Discard crops showing obvious spoilage.

Harvest & Storage

Harvest approximately:

14–21 days from sowing

Nasturtium microgreens are generally ready when:

• stems are upright and well developed;
• rounded leaves have fully opened;
• foliage is fresh green to blue-green;
• the crop has developed its characteristic peppery flavour;
• shoots are approximately 7–12cm tall; and
• stems and leaves remain tender.

Cut cleanly just above the growing medium using clean scissors or a sharp harvesting knife.

Where practical, harvest when the foliage is relatively dry.

For additional guidance, see How to Harvest & Store Microgreens.

Refrigerate promptly in a clean container and avoid crushing or tightly packing the broad leaves.

Culinary Use

Fresh Nasturtium microgreens work particularly well with:

• salads;
• sandwiches and wraps;
• sushi;
• seafood;
• eggs;
• savoury bowls; and
• plated garnishes.

Their flavour is relatively strong, so a small amount is often sufficient.

Growing Nasturtium to Maturity

Nasturtium can also be grown beyond the microgreen stage.

For mature plants:

1. Sow into pots, containers or prepared garden soil.
2. Provide a sunny to partly shaded position.
3. Use freely draining soil.
4. Avoid excessively rich fertiliser regimes.
5. Maintain regular moisture during establishment.
6. Allow adequate space for mature growth.

Mature Nasturtium develops distinctive rounded leaves and colourful flowers, both of which have established culinary uses.

Clean Growing / Food Safety

Use clean soaking containers, trays, fresh growing medium, drinking-quality water and clean harvesting equipment.

Pay particular attention to:

• rinsing seed before soaking;
• complete drainage after soaking;
• avoiding excessive seed overlap;
• avoiding permanent saturation;
• maintaining good airflow;
• using clean harvesting tools; and
• refrigerating harvested shoots promptly.

Discard crops showing:

• visible mould;
• slime;
• deteriorating seeds;
• abnormal discolouration;
• sour or unpleasant smells; or
• other signs of spoilage.

Seed Storage

Store unused Nasturtium seed sealed in a cool, dry and dark place away from heat, moisture and direct sunlight.

For longer-term storage, refrigeration can help maintain seed viability. Keep refrigerated seed sealed while it returns to room temperature before opening to reduce condensation.