Vermiculite

Vermiculite is a heat-expanded layered mineral that holds water and some dissolved nutrients within its flakes.

It is most useful in propagation and fine-rooted mixes where even moisture is beneficial.

• Mixing: blend lightly through seed compost, coir or a suitable fine substrate.
• Water behaviour: increases moisture retention; use less where drying is already slow.
• Particle care: handle gently and keep unused material dry.
• Nutrition: it is a substrate amendment, not a complete fertiliser.
• Texture and moisture behaviour vary with particle size and the other ingredients in the mix.

• As a soil additive for moisture-loving plants: mix 10–30 % vermiculite into potting soil to increase water retention for species such as Alocasia, Calathea and many ferns.
• Seed germination: sow seeds in a 1:1 blend of vermiculite and coco coir or use a layer of vermiculite on top of seed compost to maintain even moisture.
• Propagation boxes: fill a container with moist vermiculite alone or mixed with coco coir, then insert cuttings so nodes sit in the damp zone.
• Bulb and tuber storage: pack dormant bulbs (for example Caladiums or Stephania) in barely moist vermiculite to buffer humidity and reduce shrivelling.
• Mixes that dry too fast: add a small percentage of vermiculite to existing recipes if pots are drying out faster than your schedule allows.
• Water quality: because vermiculite holds so much water, use sensible fertiliser doses – it will keep salts in the substrate longer than very free-draining mixes.

• Moisture profile: vermiculite holds more water than perlite, making it better suited to plants and setups that must not dry out completely.
• Drainage: perlite drains faster and suits most aroids, succulents and plants that need good airflow at the roots.
• Where vermiculite wins: seed trays, cuttings that hate drying out, thin-rooted tropicals and bulb storage mixes.
• Balanced approach: combining vermiculite and perlite in one mix can give a middle ground for species that like moisture but still need good aeration.
• Visual cue: vermiculite flakes are brown-gold and layered, perlite is white and bead-like – mixing both makes it easy to see how much of each you are using.