Fertilising guide
How to fertilise Begonia 'Passing Storm' (Begonia rex-cultorum 'Passing Storm')— schedule & NPK
Also called passing storm begonia, rex passing storm.
More about begonia 'passing storm'
About Begonia 'Passing Storm'
Begonia rex-cultorum 'Passing Storm' · also called passing storm begonia, rex passing storm · houseplant
Begonia 'Passing Storm' is a Rex-cultorum hybrid grown for dramatic foliage: dark, near-black centers and margins surrounding a swirl of silver-pink, on spiraled, asymmetric leaves. Rex begonias are foliage plants that demand bright indirect light, high humidity, warmth, and careful watering, going semi-dormant in winter. The flowers are insignificant compared with the leaves.
Growth habit: Rhizomatous foliage begonia forming a low mound from a creeping surface rhizome; leaves arise on stalks directly from the rhizome rather than upright canes.
Watch for — Winter leaf loss: Many Rex begonias drop leaves and go semi-dormant in winter. Reduce watering and stop feeding; new growth resumes from the rhizome in spring.
What fertiliser begonia 'passing storm' actually wants — and why
Begonia 'Passing Storm' 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 'passing storm': 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 'passing storm', 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 'passing storm':
Feed every 3-4 weeks in spring and summer with a balanced liquid fertilizer at half strength. Stop feeding entirely when growth slows and the plant rests in autumn and winter. 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 'passing storm' 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 'passing storm'
Half strength every feed is the sweet spot for begonia 'passing storm': 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 'passing storm' first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the begonia 'passing storm' watering schedule.
Signs you are over-feeding begonia 'passing storm'
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for begonia 'passing storm':
- 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 'passing storm'
- 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 'passing storm' 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 'passing storm' 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 'passing storm'
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 'passing storm' — frequently asked questions
What fertiliser does begonia 'passing storm' 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 'Passing Storm' 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 'passing storm'?
Feed every 3-4 weeks in spring and summer with a balanced liquid fertilizer at half strength. Stop feeding entirely when growth slows and the plant rests in autumn and winter. Feed every 3-4 weeks in spring and summer with a balanced liquid fertilizer at half strength. Stop feeding entirely when growth slows and the plant rests in autumn and winter. 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 'passing storm'?
Half strength every feed is the sweet spot for begonia 'passing storm': frequent enough to fuel fast growth, dilute enough that it never scorches even when you feed often.
What does over-feeding begonia 'passing storm' 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 'passing storm'?
Because you feed often, salts accumulate faster — flush the pot of begonia 'passing storm' with plain water until it drains freely roughly every month through the feeding season to keep the root zone clean.
Keep reading
- Begonia 'Passing Storm' care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water begonia 'passing storm' — 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