Growing Medium Mix Ratios — Blend Your Own with Raw Coco Coir
A growing medium is what plants grow in (in pots, beds, trays or grow bags). It needs to do three things: hold water, let roots breathe (air space), and support nutrition.
These mixes show how to use coco coir as the water-holding part of a complete growing medium. On its own, coco coir holds water well but contains very few nutrients, so most plants also need compost and/or an aeration material (such as perlite) plus a suitable fertiliser programme.
All ratios are by volume (parts), not by weight. Fully hydrate and fluff your coco coir brick before measuring and mixing.
Seed Sowing Mix (Fine)
60% coco coir, 30% fine seed compost, 10% vermiculite.
Fine, evenly moist mix for germination; vermiculite holds moisture better than perlite for seed work. Start very light feeding once true leaves appear.
Young Plants & Cuttings
55% coco coir, 30% compost, 15% perlite.
Airier mix to drive quick root growth and reduce damping-off risk. Begin a balanced fertiliser programme once plants establish.
General Potting Mix (All-Purpose)
50% coco coir, 30% compost, 20% perlite or fine bark.
A dependable all-round container mix: coco holds moisture, perlite/bark keeps air spaces open. Feed regularly after the compost’s initial nutrients reduce.
Tomatoes/Peppers (containers)
60% coco coir, 25% compost, 15% perlite.
Moisture-stable and free-draining for heavy cropping in pots. Requires consistent feeding through the season (coco is low in nutrients).
Hydroponics
100% buffered coco coir in grow bags; feed with a complete nutrient solution.
Buffered coco supports more predictable nutrient behaviour in controlled feeding; water to run-off and discard run-off (drain-to-waste).
Strawberries
50% coco coir, 30% compost, 20% perlite.
Free-draining but moisture-stable for healthy roots and fruit quality. Avoid over-fertilising and do not let salts build up.
Leafy Greens & Herbs
60% coco coir, 25% compost, 15% perlite.
Even moisture for shallow roots with extra aeration to prevent soggy trays. Use steady, light feeding for best leaf quality.
Houseplants
50% coco coir, 30% compost, 10% orchid bark, 10% perlite.
Chunkier structure improves airflow and reduces compaction. Allow the top layer to dry slightly between waterings.
Microgreens
100% coco coir (fine grade), pre-moistened.
For short cycles, water may be enough; for longer grows, use a very dilute feed. Keep trays clean and avoid overwatering.
Pro tip: All ratios are guides — adjust perlite up in heavier composts, or reduce if using a very open bark-based mix. The goal is a medium that holds moisture evenly but never stays saturated.
Questions about your specific crop or setup? Contact our grow team.
🧮 Not Sure How Much You Need?
Use our free calculator to work out the exact amount of coco coir for your setup — including mix ratios.
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