Fertilising guide
How to fertilise Begonia 'Black Fang' (Begonia × 'Black Fang')— schedule & NPK
Also called black fang begonia, dark rhizomatous begonia.
More about begonia 'black fang'
About Begonia 'Black Fang'
Begonia × 'Black Fang' · also called black fang begonia, dark rhizomatous begonia · houseplant
Begonia 'Black Fang' is a dramatic rhizomatous hybrid with large, deeply jagged, near-black to dark-purple leaves edged with toothy lobes and a slightly metallic sheen. Grown chiefly for its bold gothic foliage, it spreads on a creeping rhizome. Give it bright indirect light, a shallow well-drained pot, careful watering, and warm humid air for the darkest colour.
Growth habit: Rhizomatous begonia with a creeping surface rhizome and large, jagged, near-black palmate leaves; mounding and spreading rather than upright.
What fertiliser begonia 'black fang' actually wants — and why
Begonia 'Black Fang' is a genuinely hungry tropical — in bright warmth it pushes growth fast and rewards a regular half-strength balanced feed all season.
A balanced liquid feed (even N-P-K) or a slightly nitrogen-leaning foliage feed — this is a big-leaved foliage plant putting on real size, so it wants steady nitrogen for lush leaves, not a bloom formula.
For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for begonia 'black fang': match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.
How often to feed begonia 'black fang', and which months
Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For begonia 'black fang':
Feed every 3-4 weeks in spring and summer with a balanced liquid fertiliser at half strength. Rhizomatous types are light feeders, so avoid over-fertilising. Stop feeding in winter when growth pauses. For a fast grower like this that means feeding regularly — about every 3-4 weeks — right through spring through early autumn (roughly March to September), tapering off only as light drops in autumn.
The dormant-season rule matters more than the exact interval: skip feeding entirely when begonia 'black fang' is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.
What strength to mix for begonia 'black fang'
Half strength every feed is the sweet spot for begonia 'black fang': frequent enough to fuel fast growth, dilute enough that it never scorches even when you feed often.
Feeding always goes onto already-damp soil, never dry roots — water begonia 'black fang' first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the begonia 'black fang' watering schedule.
Signs you are over-feeding begonia 'black fang'
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for begonia 'black fang':
- Brown, scorched leaf tips and margins despite correct watering.
- A white salt crust on the soil or around the pot edge.
- Sudden leaf yellowing and drop shortly after a strong feed.
- Soft, weak, over-stretched growth that cannot support itself.
Signs you are under-feeding begonia 'black fang'
- New leaves coming in noticeably smaller than older ones.
- Pale, yellow-green older leaves and slow growth through peak summer.
- A general loss of vigour and gloss in a plant that should be racing away.
If the symptoms point at watering, light or roots rather than nutrition, the full begonia 'black fang' care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Because you feed often, salts accumulate faster — flush the pot of begonia 'black fang' with plain water until it drains freely roughly every month through the feeding season to keep the root zone clean.
Organic vs synthetic feeds for begonia 'black fang'
Organic options
A diluted seaweed or fish-and-seaweed feed plus a yearly top-dress of worm castings supports fast growth without burn risk. UK: Westland seaweed or Baby Bio Organic; US: Neptune's Harvest or Espoma Indoor!.
Synthetic / liquid feeds
A balanced houseplant liquid at half strength applied frequently — UK: Baby Bio, Phostrogen or Westland Houseplant Feed; US: Miracle-Gro Indoor Plant Food or Dyna-Gro Foliage-Pro for steady leafy growth.
Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.
Fertilising begonia 'black fang' — frequently asked questions
What fertiliser does begonia 'black fang' need?
A balanced liquid feed (even N-P-K) or a slightly nitrogen-leaning foliage feed — this is a big-leaved foliage plant putting on real size, so it wants steady nitrogen for lush leaves, not a bloom formula. Begonia 'Black Fang' is a genuinely hungry tropical — in bright warmth it pushes growth fast and rewards a regular half-strength balanced feed all season.
How often should I feed begonia 'black fang'?
Feed every 3-4 weeks in spring and summer with a balanced liquid fertiliser at half strength. Rhizomatous types are light feeders, so avoid over-fertilising. Stop feeding in winter when growth pauses. Feed every 3-4 weeks in spring and summer with a balanced liquid fertiliser at half strength. Rhizomatous types are light feeders, so avoid over-fertilising. Stop feeding in winter when growth pauses. For a fast grower like this that means feeding regularly — about every 3-4 weeks — right through spring through early autumn (roughly March to September), tapering off only as light drops in autumn.
What strength of feed for begonia 'black fang'?
Half strength every feed is the sweet spot for begonia 'black fang': frequent enough to fuel fast growth, dilute enough that it never scorches even when you feed often.
What does over-feeding begonia 'black fang' look like?
Brown, scorched leaf tips and margins despite correct watering. A white salt crust on the soil or around the pot edge. Sudden leaf yellowing and drop shortly after a strong feed. Soft, weak, over-stretched growth that cannot support itself. The mistake here is the opposite of most houseplants: under-feeding a fast tropical in peak season starves it, leaving small, pale new leaves and slow growth — but full-strength doses still burn it, so feed often and weak, not occasionally and strong.
Should I flush the soil of begonia 'black fang'?
Because you feed often, salts accumulate faster — flush the pot of begonia 'black fang' with plain water until it drains freely roughly every month through the feeding season to keep the root zone clean.
Keep reading
- Begonia 'Black Fang' care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water begonia 'black fang' — the watering schedule
- The houseplant fertiliser schedule — feeding through the year
- NPK ratio explained — what the three numbers on the bottle mean
- How to fertilise snake plant
- How to fertilise dracaena
- How to fertilise peperomia
- All 2464 fertilising guides in the Growli library