Fertilising guide
How to fertilise Tongue Water Trumpet (Cryptocoryne lingua)— schedule & NPK
Also called Tongue Crypt, Tongue-Leaved Water Trumpet, Borneo Crypt.
More about tongue water trumpet
About Tongue Water Trumpet
Cryptocoryne lingua · also called Tongue Crypt, Tongue-Leaved Water Trumpet · tropical
Cryptocoryne lingua is a distinctive Bornean aquatic aroid with thick, tongue-shaped, leathery leaves adapted to tidal or brackish-influenced streams. It is among the most unusual Cryptocoryne species and is prized by specialist aquatic plant enthusiasts. Tolerates a wider range of water chemistry than most crypts. Toxic to pets as an aroid.
Growth habit: Compact rosette-forming aquatic perennial with distinctive thick, leathery tongue-shaped leaves
What fertiliser tongue water trumpet actually wants — and why
Tongue Water Trumpet 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 tongue water trumpet: 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 tongue water trumpet, 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 tongue water trumpet:
Apply aquatic root tabs once every 3–4 months. This species is not a heavy feeder — excess fertilisation promotes algae more than plant growth. Stable, clean water with light fertilisation is preferable to aggressive feeding. 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 tongue water trumpet 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 tongue water trumpet
Half strength every feed is the sweet spot for tongue water trumpet: 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 tongue water trumpet first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the tongue water trumpet watering schedule.
Signs you are over-feeding tongue water trumpet
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for tongue water trumpet:
- 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 tongue water trumpet
- 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 tongue water trumpet 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 tongue water trumpet 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 tongue water trumpet
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 tongue water trumpet — frequently asked questions
What fertiliser does tongue water trumpet 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. Tongue Water Trumpet 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 tongue water trumpet?
Apply aquatic root tabs once every 3–4 months. This species is not a heavy feeder — excess fertilisation promotes algae more than plant growth. Stable, clean water with light fertilisation is preferable to aggressive feeding. Apply aquatic root tabs once every 3–4 months. This species is not a heavy feeder — excess fertilisation promotes algae more than plant growth. Stable, clean water with light fertilisation is preferable to aggressive feeding. 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 tongue water trumpet?
Half strength every feed is the sweet spot for tongue water trumpet: frequent enough to fuel fast growth, dilute enough that it never scorches even when you feed often.
What does over-feeding tongue water trumpet 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 tongue water trumpet?
Because you feed often, salts accumulate faster — flush the pot of tongue water trumpet with plain water until it drains freely roughly every month through the feeding season to keep the root zone clean.
Keep reading
- Tongue Water Trumpet care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water tongue water trumpet — 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 fringed coelogyne
- How to fertilise rothschild's cirrhopetalum
- How to fertilise medusa's cirrhopetalum
- All 11687 fertilising guides in the Growli library