Fertilising guide

How to fertilise Pelargonium citronellum (Pelargonium citronellum)— schedule & NPK

Also called Citronella geranium, Mosquito plant, Lemon pelargonium.

More about pelargonium citronellum

About Pelargonium citronellum

Pelargonium citronellum · also called Citronella geranium, Mosquito plant · herb

Pelargonium citronellum is a robust scented geranium with rough, deeply lobed leaves that smell strongly of lemon-citronella when touched. Often sold as the 'mosquito plant', its fragrance does not actually repel insects in the air. A tall, vigorous South African species, it bears pink flowers and demands full sun, sharp drainage and a frost-free winter.

Growth habit: Tall, vigorous, upright evergreen subshrub with stiff stems and large, rough, sharply lobed lemon-scented leaves; can become woody and benefits from hard pinching and pruning.

What fertiliser pelargonium citronellum actually wants — and why

Pelargonium citronellum 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 pelargonium citronellum: 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 pelargonium citronellum, 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 pelargonium citronellum:

Feed every 3-4 weeks in spring and summer with a balanced or high-potash liquid feed; this vigorous grower needs only moderate nitrogen. Suspend feeding in autumn and winter. 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 pelargonium citronellum 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 pelargonium citronellum

Half strength is a sensible default for pelargonium citronellum — 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 pelargonium citronellum first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the pelargonium citronellum watering schedule.

Signs you are over-feeding pelargonium citronellum

Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for pelargonium citronellum:

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 pelargonium citronellum

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 pelargonium citronellum care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

Pot-grown pelargonium citronellum 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 pelargonium citronellum

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 pelargonium citronellum — frequently asked questions

What fertiliser does pelargonium citronellum 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. Pelargonium citronellum 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 pelargonium citronellum?

Feed every 3-4 weeks in spring and summer with a balanced or high-potash liquid feed; this vigorous grower needs only moderate nitrogen. Suspend feeding in autumn and winter. Feed every 3-4 weeks in spring and summer with a balanced or high-potash liquid feed; this vigorous grower needs only moderate nitrogen. Suspend feeding in autumn and winter. 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 pelargonium citronellum?