Fertilising guide
How to fertilise Cryptocoryne undulata (Cryptocoryne undulata)— schedule & NPK
Also called undulate Crypt, wavy Cryptocoryne.
More about cryptocoryne undulata
About Cryptocoryne undulata
Cryptocoryne undulata · also called undulate Crypt, wavy Cryptocoryne · tropical
Cryptocoryne undulata is a Sri Lankan water trumpet with narrow, wavy-edged brownish-green leaves forming a 10-25 cm midground rosette. Hardy and adaptable to varied water chemistry and low light, it spreads by runners into a textured stand. A reliable Crypt for community planted tanks, prone to the usual post-transplant melt before it rebounds.
Growth habit: Low-to-medium clumping rosette spreading by runners into a textured midground stand.
Watch for — Algae on old leaves: Slow growth under strong light invites algae; balance light with nutrients/CO2 and trim affected leaves.
What fertiliser cryptocoryne undulata actually wants — and why
Cryptocoryne undulata is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.
A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root 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 cryptocoryne undulata: 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 cryptocoryne undulata, 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 cryptocoryne undulata:
Feed at the roots with substrate tabs every 2-3 months; a balanced liquid fertiliser with iron and potassium supports the wavy leaves. CO2 speeds growth and intensifies colour but is optional for this forgiving species. Treat that as every 2-3 months between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.
The dormant-season rule matters more than the exact interval: skip feeding entirely when cryptocoryne undulata 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 cryptocoryne undulata
Half strength is the safe default for cryptocoryne undulata — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
Feeding always goes onto already-damp soil, never dry roots — water cryptocoryne undulata first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the cryptocoryne undulata watering schedule.
Signs you are over-feeding cryptocoryne undulata
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for cryptocoryne undulata:
- Brown, crispy leaf tips and edges with no sign of underwatering.
- A white, crusty salt deposit on the soil surface or pot rim.
- Weak, pale, stretched new growth that flops.
- Lower leaves yellow and drop while the soil is correctly watered.
Signs you are under-feeding cryptocoryne undulata
- Uniformly pale or yellow-green leaves, oldest first.
- Noticeably small new leaves and stalled growth in good light and season.
- A generally tired, lacklustre look despite correct watering and light.
If the symptoms point at watering, light or roots rather than nutrition, the full cryptocoryne undulata care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of cryptocoryne undulata with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.
Organic vs synthetic feeds for cryptocoryne undulata
Organic options
A diluted seaweed or worm-casting feed, or fish emulsion if you can tolerate the smell indoors. UK: Westland or Baby Bio Organic, dilute seaweed; US: Espoma Indoor! or Neptune's Harvest fish & seaweed. Slow, gentle and hard to overdo.
Synthetic / liquid feeds
A general-purpose houseplant liquid at half strength — UK: Baby Bio, Westland Houseplant Feed or Phostrogen; US: Miracle-Gro Indoor Plant Food or Schultz. Convenient and fast-acting; the only risk is overdoing it.
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 cryptocoryne undulata — frequently asked questions
What fertiliser does cryptocoryne undulata need?
A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula. Cryptocoryne undulata is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.
How often should I feed cryptocoryne undulata?
Feed at the roots with substrate tabs every 2-3 months; a balanced liquid fertiliser with iron and potassium supports the wavy leaves. CO2 speeds growth and intensifies colour but is optional for this forgiving species. Feed at the roots with substrate tabs every 2-3 months; a balanced liquid fertiliser with iron and potassium supports the wavy leaves. CO2 speeds growth and intensifies colour but is optional for this forgiving species. Treat that as every 2-3 months between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.
What strength of feed for cryptocoryne undulata?
Half strength is the safe default for cryptocoryne undulata — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding cryptocoryne undulata look like?
Brown, crispy leaf tips and edges with no sign of underwatering. A white, crusty salt deposit on the soil surface or pot rim. Weak, pale, stretched new growth that flops. Lower leaves yellow and drop while the soil is correctly watered. Feeding cryptocoryne undulata year-round on a fixed schedule, including dark winter months, is the most common mistake — it cannot use the nutrients in low light and the surplus simply burns the roots and crusts the soil.
Should I flush the soil of cryptocoryne undulata?
Flush the pot of cryptocoryne undulata with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.
Keep reading
- Cryptocoryne undulata care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water cryptocoryne undulata — 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 monstera
- How to fertilise pothos
- How to fertilise fiddle leaf fig
- All 5561 fertilising guides in the Growli library