Give young plants the perfect launchpad and they’ll repay you all season.
Why Seedlings Need a Special Mix
Regular garden soil is heavy, inconsistent and teeming with pathogens that love nothing more than wiping out delicate sprouts. A seed-raising medium must:
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Stay light and fluffy so roots can push through.
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Hold moisture without turning waterlogged.
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Contain only a whisper of nutrients – too much salt or nitrogen burns baby roots.
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Be pest- and disease-free to keep damping-off at bay.
Core Ingredients Explained
|
Ingredient |
What it Brings |
Where to Get It |
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Coco Coir |
Superb moisture retention, pH-stable |
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Peat Moss |
Acid-leaning structure, holds air pockets |
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Perlite |
Extra drainage & oxygen |
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Sieved Compost |
Gentle nutrient background & microbes |
Tip: Keep a 20L bag of these bases on hand – they’re the backbone of every good seed-raising mix.
For seedlings that will eventually be planted into garden beds or fruiting systems, Mycorrhizal Fungi in Australian Gardens: The 2025 Ultimate Guide shows when to introduce fungi so young roots establish faster outdoors.
Ideal Texture, pH & Nutrient Levels
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Texture – Aim for a crumble that compacts when squeezed yet breaks apart with a nudge.
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pH – 6.0 – 6.5 is the butter zone; test with a simple soil strip.
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EC (Electrical Conductivity) – Stay under 1.0 mS/cm to avoid fertiliser burn.
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Sterility – Bake DIY batches at 90 °C for 30 min or steam for 10 min to eliminate fungal spores.
DIY Seed-Raising Mix Recipe (Makes ~10 L)
|
Component |
Parts (vol) |
|
Coco Coir (hydrated brick) |
4 |
|
Perlite |
1 |
|
Fine-grade Sieved Compost |
1 |
|
Worm Castings (optional booster) |
½ |
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Hydrate the coir until fluffy.
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Combine all ingredients gently – don’t crush the perlite.
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Moisten until it clumps but doesn’t drip.
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Cool / Sterilise if you heated it.
Your mix should feel feather-light yet stay damp for 24 h.
Prefer Ready-Made? Grab Our Seed Raising Mix
Short on time or bench space? Dr Greenthumbs Seed Raising Potting Mix is blended by horticultural pros with:
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High-grade coco coir for moisture control
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Perlite for unbeatable aeration
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Sieved compost for gentle nutrition
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Zero fillers or nasties – just open the bag and fill your trays™
Spend less time mixing and more time sowing.
Step-by-Step: Filling Trays & Sowing
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Pre-moisten the mix until it’s evenly damp.
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Fill cells, tapping lightly – don’t compress.
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Sow seeds at twice their thickness.
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Bottom-water trays so the surface stays friable.
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Cover with a clear dome or cling film until green tips appear.
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Vent & Light – Remove cover, place under bright light, 18 – 24 °C ideal.
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Feed Lightly – After two true leaves, dose with a ¼-strength organic liquid feed.
Troubleshooting Common Issues
|
Symptom |
Likely Cause |
Quick Fix |
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Fuzzy white mould |
Excess humidity |
Increase airflow, skim surface |
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Spindly, toppled seedlings |
Low light or heat |
Add LED grow-light, lower dome temp |
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Yellow cotyledons |
Over-watering |
Let mix dry slightly, bottom-water only |
When to Pot-Up with GreenSpace Premium
Once roots poke from cell bases, shift seedlings to GreenSpace Premium Potting Soil – a chunky, microbe-rich blend with worm castings and optimal air pockets for explosive veg growth. Available in 8 L, 27 L and 45 L bags to suit every project.
FAQ
Can I reuse seed-raising mix?
Only if you sterilise it first; pathogens build up fast.
Is this mix good for cuttings?
Yes – the airy structure is perfect for strike cuttings.
How wet should the mix stay?
Damp like a wrung-out sponge; water from below to keep foliage dry.
Happy germinating, legends – and remember, great gardens start with great soil! 🌿
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