Fertilising guide
How to fertilise Citron (Citrus medica)— schedule & NPK
Also called Citron, Buddha's hand, Corsican citron, Etrog.
More about citron
About Citron
Citrus medica · also called Citron, Buddha's hand · edible
Citron is one of the original three ancestral Citrus species, grown for its enormous, fragrant, thick-rinded fruit rather than juice. The Buddha's hand form (var. sarcodactylis) is fingered and entirely pith with no pulp. Used for candied peel, liqueurs, perfumery, and religious ritual. Tender and best grown in sheltered warm conditions or large containers.
Growth habit: Evergreen large shrub or small tree with irregular, spreading branches
Watch for — Scale insects and mealybugs: The soft stems and dense growth provide shelter for sap-feeding insects. Inspect under leaves and at branch junctions regularly; treat with horticultural oil or neem-based products.
What fertiliser citron actually wants — and why
Citron feeds in two distinct phases — balanced to build the plant, then high-potassium the moment flowering starts to set and fill a heavy crop.
Balanced (even N-P-K) at planting for roots and frame, then switch to a high-potassium ("high-potash") tomato-style feed once the first flowers open — potassium is what sizes and ripens fruit, not nitrogen.
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 citron: 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 citron, 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 citron:
Apply a balanced citrus fertiliser every 3-4 weeks from spring through autumn. Citron's vigorous growth and large fruit require generous potassium and phosphorus as fruit develops. Supplement with foliar sprays of chelated micronutrients if leaf yellowing appears. So: a balanced feed or compost at planting, then a high-potash liquid every 1-2 weeks from first flower through harvest across the main season (spring through early autumn).
The dormant-season rule matters more than the exact interval: skip feeding entirely when citron 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 citron
Follow the crop-feed label rate for citron — these are calibrated for hungry vegetables. Consistency through fruiting matters more than strength; erratic feeding causes problems like blossom-end rot.
Feeding always goes onto already-damp soil, never dry roots — water citron first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the citron watering schedule.
Signs you are over-feeding citron
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for citron:
- Vigorous dark-green leafy growth but few flowers or fruit (excess nitrogen).
- Lush foliage hiding the crop; soft growth prone to pests and disease.
- Salt crust on the soil and scorched leaf edges in containers.
Signs you are under-feeding citron
- Pale, yellowing lower leaves and stunted growth.
- Small fruit, poor set, and a quickly exhausted plant.
- Blossom-end rot and weak cropping from erratic or insufficient feeding.
If the symptoms point at watering, light or roots rather than nutrition, the full citron care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
In containers, fertiliser salts build up fast — water citron thoroughly so excess drains from the base each time, and flush pots with plain water every few weeks to prevent a damaging salt build-up.
Organic vs synthetic feeds for citron
Organic options
Garden compost or well-rotted manure dug in before planting, plus a liquid comfrey or seaweed feed once fruiting starts. UK: comfrey feed or organic Tomorite; US: Espoma Tomato-tone or Neptune's Harvest. Builds soil and feeds in one.
Synthetic / liquid feeds
A balanced feed at planting then a high-potash tomato feed in fruiting — UK: Growmore at planting then Tomorite (Levington) or Phostrogen; US: a balanced 10-10-10 then Miracle-Gro Tomato or a bloom booster.
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 citron — frequently asked questions
What fertiliser does citron need?
Balanced (even N-P-K) at planting for roots and frame, then switch to a high-potassium ("high-potash") tomato-style feed once the first flowers open — potassium is what sizes and ripens fruit, not nitrogen. Citron feeds in two distinct phases — balanced to build the plant, then high-potassium the moment flowering starts to set and fill a heavy crop.
How often should I feed citron?
Apply a balanced citrus fertiliser every 3-4 weeks from spring through autumn. Citron's vigorous growth and large fruit require generous potassium and phosphorus as fruit develops. Supplement with foliar sprays of chelated micronutrients if leaf yellowing appears. Apply a balanced citrus fertiliser every 3-4 weeks from spring through autumn. Citron's vigorous growth and large fruit require generous potassium and phosphorus as fruit develops. Supplement with foliar sprays of chelated micronutrients if leaf yellowing appears. So: a balanced feed or compost at planting, then a high-potash liquid every 1-2 weeks from first flower through harvest across the main season (spring through early autumn).
What strength of feed for citron?
Follow the crop-feed label rate for citron — these are calibrated for hungry vegetables. Consistency through fruiting matters more than strength; erratic feeding causes problems like blossom-end rot.
What does over-feeding citron look like?
Vigorous dark-green leafy growth but few flowers or fruit (excess nitrogen). Lush foliage hiding the crop; soft growth prone to pests and disease. Salt crust on the soil and scorched leaf edges in containers. Staying on a high-nitrogen feed once citron starts flowering is the classic error — you get a huge leafy plant and a disappointing crop. Switch to high-potash the moment flowers appear.
Should I flush the soil of citron?
In containers, fertiliser salts build up fast — water citron thoroughly so excess drains from the base each time, and flush pots with plain water every few weeks to prevent a damaging salt build-up.
Keep reading
- Citron care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water citron — 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 lettuce
- How to fertilise bean
- How to fertilise garlic
- All 6887 fertilising guides in the Growli library