In short: Bulb fibre is simply a light, clean, moisture-holding compost for growing bulbs in bowls and pots — and coco coir is the peat-free material that modern bulb fibres are built on. For indoor bowls without drainage holes, mix expanded coir with a little horticultural charcoal and grit; for pots with drainage, blend coir with peat-free compost and grit. Prepared hyacinths planted in September or early October and kept cool and dark for 8–10 weeks will flower for Christmas; paperwhites need no chilling and flower in 4–6 weeks; amaryllis potted in October or November flowers in 6–8 weeks. One 5 kg brick makes about 75 litres — enough for roughly 25 bowls.
What bulb fibre actually is
Bulb fibre is not a feed and not a special soil. It is a low-nutrient, open, water-retentive growing medium designed for bulbs grown in decorative bowls that have no drainage hole. Traditional bulb fibre was peat with a little charcoal and crushed oyster shell added to keep it "sweet" when the bowl sits wet. Peat-free bulb fibres do the same job with coco coir, the fine pith from coconut husks, because coir holds water while staying airy and, unlike peat, re-wets easily if it dries out in a warm room. The Royal Horticultural Society's advice for Christmas-flowering bulbs is that the simplest compost to choose is peat-free bulb fibre, especially for bowls without drainage.
Bulbs carry their own food for the first season's flowers, which is why the medium can be almost nutrient-free. What they need from it is moisture without waterlogging, room for roots, and something that will not turn sour in a bowl that never drains.
Peat-free bulb fibre from a coco coir brick — two recipes
| Use | Recipe (by volume) | Notes |
|---|---|---|
| Indoor bowls without drainage (hyacinths, paperwhites, crocus, dwarf iris) | 8 parts damp expanded coir : 1 part horticultural charcoal : 1 part horticultural grit or crushed oyster shell | The charcoal keeps a sealed bowl fresh; the grit adds a little weight and drainage. Water sparingly — moist, never with free water in the base. |
| Pots with drainage holes (amaryllis, bulb "lasagne" pots, outdoor tulips and daffodils) | 2 parts coir : 1 part peat-free multipurpose compost : 1 part grit or perlite | Free drainage matters more than water-holding here. The compost adds a little nutrition for bulbs you intend to keep. |
Expand the brick first — 20 litres of water, 20–30 minutes — then let the surplus drain so the coir is damp rather than wet before you mix. Use washed, calcium-buffered coir with a stated pH (5.5–6.5) and low EC: raw, unwashed coir can carry enough salt to check the fine feeding roots that bulbs push out in the dark. Why buffering matters.
How much do you need?
| Container | Approximate volume of mix | From one 5 kg brick (≈75 L) |
|---|---|---|
| 15 cm bowl (3 hyacinths) | 1.5 L | ≈ 50 bowls |
| 20 cm bowl (5 hyacinths or 6–8 paperwhites) | 3 L | ≈ 25 bowls |
| Amaryllis in a 15 cm pot | 1.5 L | ≈ 50 pots |
| 30 cm bulb lasagne pot | 12–15 L (about half of it coir) | ≈ 10–12 pots |
Unused expanded coir keeps indefinitely once it has dried out, so make what you need and store the rest — see storing coco coir.
Forcing hyacinths for Christmas, step by step
- Buy "prepared" bulbs. These have been pre-chilled by the supplier so they flower early. Ordinary hyacinths will still flower indoors, just later. Wear gloves — hyacinth bulbs can irritate skin.
- Plant by late September to mid-October. The RHS timing for Christmas flowers is to plant 'Pink Pearl' by 24 September or 'Anna Marie' by 12 October. Later plantings flower in January and February, which is no bad thing.
- Half-fill the bowl with the damp bulb fibre mix, set the bulbs close together but not touching, and fill in so the tips ("noses") sit just above the surface.
- Keep cool and dark for 8–10 weeks — ideally around 9 °C: a garage, shed, cool cupboard or a box in a north-facing porch. Check every couple of weeks and water only if the fibre is drying out.
- Bring in when the shoots are about 5 cm tall. Give them a cool, light room for a week, then a warmer spot. The RHS reckons on 18–22 days indoors from that point to flowering.
- After flowering, plant the bulbs out in the garden. They will not force again, but they will flower outdoors in future springs.
Paperwhites and amaryllis — no chilling needed
Paperwhite narcissi do not need a cold period. Plant them in bulb fibre in September or October (or in batches through to January) with the tips showing, keep them cool and light, and they flower in roughly 4–6 weeks. Plant a bowl every fortnight for a run of flowers through the winter. Their stems flop in a warm room; a cool windowsill and a few twigs for support solve it.
Amaryllis (Hippeastrum) wants a pot only a little wider than the bulb, with drainage. Use the free-draining recipe, set the bulb with its top third above the mix, water once, then keep it warm and barely watered until the flower stem appears. Flowers arrive in 6–8 weeks, so a bulb potted in mid-October flowers around Christmas and one potted in late November flowers in January.
Bulbs in outdoor pots — the lasagne method
For a spring display in a big pot, plant in layers: tulips at the bottom (about 20 cm deep), daffodils or hyacinths in the middle, and crocus, dwarf iris or muscari near the top. Use the free-draining coir mix and put crocks or a layer of grit over the drainage hole. Coir's water-holding is an advantage in pots that sit against a house wall and miss the rain, and its light weight makes a 30 cm pot movable. Feed with a high-potash liquid feed after flowering if you want to keep the bulbs for another year.
Common mistakes
- Waterlogging a bowl. A bowl without a drainage hole should be moist, never sodden. Tip it gently after watering; if water runs out, you have overdone it.
- Bringing hyacinths in too early. Short, stunted flower spikes buried in the leaves are the sign. Wait for 5 cm of shoot and a full 8–10 weeks in the cold.
- Using garden soil or manure-rich compost. Bulbs rot in heavy, rich, wet mixes. Keep it light and lean.
- Feeding forced bulbs. Not needed — the bulb has everything the first flowers require.
- Unwashed coir. Salt residues in raw coir are the one way coir can let a bulb down. Buy washed and buffered.
Frequently asked questions
Can I use coco coir instead of bulb fibre?
Yes. Coir is the base of most peat-free bulb fibres. For a bowl with no drainage, add a little horticultural charcoal to keep it fresh; for a pot with drainage, mix it with compost and grit.
Is bulb fibre the same as compost?
No. Bulb fibre is a low-nutrient, open medium for bulbs in bowls; multipurpose compost is heavier and richer. Bulbs in bowls do better in the lighter mix.
When should I plant hyacinths for Christmas?
Prepared bulbs by late September to mid-October, then 8–10 weeks cool and dark, then two to three weeks indoors. The RHS gives 24 September for 'Pink Pearl' and 12 October for 'Anna Marie'.
Do paperwhites need bulb fibre or just water?
Either works. Bulb fibre supports the stems better and keeps the bowl fresher than a jar of water and pebbles.
Can I reuse the bulb fibre?
Yes — after flowering, tip it out, pick out the roots and let it dry. It can go into next year's pots or onto the garden. See reusing coco coir.
Is coco peat the same as coco coir?
Yes — the two names describe the same material.
One washed, calcium-buffered 5 kg brick — about 75 litres of peat-free bulb fibre base, enough for 25 bowls, delivered free across the UK.
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