Fertilising guide
How to fertilise Lemongrass (Cymbopogon citratus)— schedule & NPK
Also called West Indian lemongrass, sereh, fever grass.
About Lemongrass
Cymbopogon citratus · also called West Indian lemongrass, sereh · herb
Lemongrass is a tropical clumping grass from south Asia with intensely lemon-scented stems and leaves used in Thai and Vietnamese cooking. Tender; grown as an annual or overwintered as a houseplant in cool climates. Toxic to pets due to essential oils.
Lemongrass (Cymbopogon citratus, Poaceae) is a frost-tender clumping tropical grass widely grown in the tropics and subtropics for its lemony stalks used in Southeast Asian cooking; hardy only to about USDA zones 9-10.
A heavy nitrogen feeder; the lush grassy clump responds strongly to fertile, organic-rich soil and supplemental nitrogen.
Growth habit: Clumping tropical grass
Sources: hort.extension.wisc.edu, plants.ces.ncsu.edu, missouribotanicalgarden.org
What fertiliser lemongrass actually wants — and why
Lemongrass is a soft, fast leafy herb that you harvest hard — a modest balanced feed keeps tender growth coming without tipping it into bland or bolting.
A balanced general feed (even N-P-K) at modest strength — enough nitrogen to keep replacing the leaves you pick, but not so much that flavour thins or it bolts to seed.
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 lemongrass: 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 lemongrass, 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 lemongrass:
Balanced feed monthly during growth. In practice: a balanced liquid feed every few weeks through the main growing and harvesting season (spring through early autumn), more often the harder you are picking it.
The dormant-season rule matters more than the exact interval: skip feeding entirely when lemongrass 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 lemongrass
Half strength is a sensible default for lemongrass — enough to fuel regrowth after cutting, gentle enough that the leaves stay aromatic rather than watery.
Feeding always goes onto already-damp soil, never dry roots — water lemongrass first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the lemongrass watering schedule.
Signs you are over-feeding lemongrass
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for lemongrass:
- Fast, soft, pale growth with diluted, less aromatic flavour.
- Early bolting (running to flower) and a bitter edge.
- Salt crust and scorched tips on container plants.
Signs you are under-feeding lemongrass
- Pale, slow regrowth after cutting and small leaves.
- A tired, stalled plant that cannot keep up with harvesting.
- Yellowing older leaves in a long-spent pot.
If the symptoms point at watering, light or roots rather than nutrition, the full lemongrass care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Pot-grown lemongrass builds up feed salts quickly — water until it drains each time and flush the pot with plain water every few weeks, especially on a sunny windowsill.
Organic vs synthetic feeds for lemongrass
Organic options
A diluted seaweed feed or worm-casting tea keeps soft growth coming without overdoing it. UK: dilute seaweed or Westland; US: Espoma Garden-tone or Neptune's Harvest. Gentle, hard to overdo, flavour-friendly.
Synthetic / liquid feeds
A balanced liquid feed at half strength through harvesting — UK: Phostrogen, Baby Bio or Westland; US: Miracle-Gro all-purpose at half strength. Fast regrowth; just do not overdo the nitrogen.
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 lemongrass — frequently asked questions
What fertiliser does lemongrass need?
A balanced general feed (even N-P-K) at modest strength — enough nitrogen to keep replacing the leaves you pick, but not so much that flavour thins or it bolts to seed. Lemongrass is a soft, fast leafy herb that you harvest hard — a modest balanced feed keeps tender growth coming without tipping it into bland or bolting.
How often should I feed lemongrass?
Balanced feed monthly during growth. Balanced feed monthly during growth. In practice: a balanced liquid feed every few weeks through the main growing and harvesting season (spring through early autumn), more often the harder you are picking it.
What strength of feed for lemongrass?
Half strength is a sensible default for lemongrass — enough to fuel regrowth after cutting, gentle enough that the leaves stay aromatic rather than watery.
What does over-feeding lemongrass look like?
Fast, soft, pale growth with diluted, less aromatic flavour. Early bolting (running to flower) and a bitter edge. Salt crust and scorched tips on container plants. Over-feeding lemongrass with strong nitrogen is the usual mistake — it grows fast and lush but the leaves turn bland and it bolts to flower sooner, ending the useful harvest early.
Should I flush the soil of lemongrass?
Pot-grown lemongrass builds up feed salts quickly — water until it drains each time and flush the pot with plain water every few weeks, especially on a sunny windowsill.
Keep reading
- Lemongrass care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water lemongrass — 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 basil
- How to fertilise herb garden
- How to fertilise mint
- All 200 fertilising guides in the Growli library