Fertilising guide

How to fertilise South African Geranium (Pelargonium sidoides)— schedule & NPK

Also called South African Geranium, Umckaloabo, African Geranium.

More about south african geranium

About South African Geranium

Pelargonium sidoides · also called South African Geranium, Umckaloabo · herb

Pelargonium sidoides is a tuberous-rooted perennial species from the dry grasslands and rocky slopes of South Africa, valued both as an ornamental and as a medicinal herb — its root extract is the basis for Umckaloabo, a widely sold herbal cold and bronchitis remedy. It produces a low, velvety-silver rosette of heart-shaped leaves and abundant small, deep maroon-to-black flowers on upright stems throughout a long season. It needs very free-draining soil and dislikes wet winters, making container culture the safest approach in UK and northern US gardens. Toxic to cats and dogs.

Growth habit: Low-growing, clump-forming tuberous perennial with a basal rosette of softly hairy, silver-green heart-shaped leaves and upright flowering stems 20-40 cm tall.

What fertiliser south african geranium actually wants — and why

South African Geranium 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 south african geranium: 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 south african geranium, 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 south african geranium:

Feed monthly in spring and summer with a high-potash liquid fertiliser (tomato-type); avoid high-nitrogen feeds which promote lush, disease-prone growth at the expense of flowers. 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 south african geranium 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 south african geranium

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

Signs you are over-feeding south african geranium

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

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 south african geranium

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 south african geranium care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

Pot-grown south african geranium 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 south african geranium

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 south african geranium — frequently asked questions

What fertiliser does south african geranium 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. South African Geranium 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 south african geranium?

Feed monthly in spring and summer with a high-potash liquid fertiliser (tomato-type); avoid high-nitrogen feeds which promote lush, disease-prone growth at the expense of flowers. Feed monthly in spring and summer with a high-potash liquid fertiliser (tomato-type); avoid high-nitrogen feeds which promote lush, disease-prone growth at the expense of flowers. 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 south african geranium?