Fertilising guide
How to fertilise Philodendron Radiatum (Philodendron radiatum)— schedule & NPK
Also called Radiatum, Dubia Philodendron.
More about philodendron radiatum
About Philodendron Radiatum
Philodendron radiatum · also called Radiatum, Dubia Philodendron · houseplant
A climbing philodendron grown for its large, deeply lobed and pinnately cut leaves that look architectural and jungle-like. Widespread from Mexico to Central America, P. radiatum is a vigorous, fairly easy climber that develops increasingly divided foliage as it ascends a support in warm, humid, bright indirect conditions.
Growth habit: Vigorous climbing aroid with aerial roots; on a moss pole it climbs steadily, producing progressively larger, deeply pinnately lobed leaves with maturity.
Watch for — Brown leaf edges: Low humidity or salt buildup dries the divided leaflets. Raise humidity and flush the soil to remove excess fertiliser.
What fertiliser philodendron radiatum actually wants — and why
Philodendron Radiatum 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 philodendron radiatum: 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 philodendron radiatum, 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 philodendron radiatum:
Feed every three to four weeks in spring and summer with a balanced liquid fertiliser at half strength to support its large divided foliage. Reduce in autumn and stop in winter when growth slows. For a fast grower like this that means feeding regularly — about sparingly through the growing season — 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 philodendron radiatum 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 philodendron radiatum
Half strength every feed is the sweet spot for philodendron radiatum: 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 philodendron radiatum first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the philodendron radiatum watering schedule.
Signs you are over-feeding philodendron radiatum
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for philodendron radiatum:
- 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 philodendron radiatum
- 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 philodendron radiatum 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 philodendron radiatum 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 philodendron radiatum
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 philodendron radiatum — frequently asked questions
What fertiliser does philodendron radiatum 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. Philodendron Radiatum 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 philodendron radiatum?
Feed every three to four weeks in spring and summer with a balanced liquid fertiliser at half strength to support its large divided foliage. Reduce in autumn and stop in winter when growth slows. Feed every three to four weeks in spring and summer with a balanced liquid fertiliser at half strength to support its large divided foliage. Reduce in autumn and stop in winter when growth slows. For a fast grower like this that means feeding regularly — about sparingly through the growing season — right through spring through early autumn (roughly March to September), tapering off only as light drops in autumn.
What strength of feed for philodendron radiatum?
Half strength every feed is the sweet spot for philodendron radiatum: frequent enough to fuel fast growth, dilute enough that it never scorches even when you feed often.
What does over-feeding philodendron radiatum 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 philodendron radiatum?
Because you feed often, salts accumulate faster — flush the pot of philodendron radiatum with plain water until it drains freely roughly every month through the feeding season to keep the root zone clean.
Keep reading
- Philodendron Radiatum care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water philodendron radiatum — 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