Fertilising guide

How to fertilise Key lime (Citrus aurantifolia)— schedule & NPK

Also called Key lime, Mexican lime, West Indian lime, Bartender's lime.

More about key lime

About Key lime

Citrus aurantifolia · also called Key lime, Mexican lime · edible

Key lime is a small, thorny citrus producing aromatic, thin-skinned limes with intensely tart juice and a distinctive floral aroma. More frost-sensitive than Persian lime, it thrives in tropical and subtropical climates or sheltered containers. The highly fragrant foliage and rind contain citrus oils toxic to pets.

Growth habit: Evergreen thorny shrub or small multi-stemmed tree

What fertiliser key lime actually wants — and why

Key lime feeds in two distinct phases — balanced to build the plant, then high-potassium the moment flowering starts to set and fill a heavy crop.

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 key lime: 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 key lime, 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 key lime:

The dormant-season rule matters more than the exact interval: skip feeding entirely when key lime 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 key lime

Follow the crop-feed label rate for key lime — 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 key lime first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the key lime watering schedule.

Signs you are over-feeding key lime

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

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 key lime

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 key lime 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 key lime 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 key lime

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 key lime — frequently asked questions

What fertiliser does key lime 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. Key lime 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 key lime?

Feed every 4-6 weeks with a high-nitrogen citrus fertiliser from spring through late summer. Key limes are vigorous feeders; deficiencies in magnesium show quickly as interveinal yellowing. A slow-release citrus granule in spring plus liquid feeds through summer works well. Feed every 4-6 weeks with a high-nitrogen citrus fertiliser from spring through late summer. Key limes are vigorous feeders; deficiencies in magnesium show quickly as interveinal yellowing. A slow-release citrus granule in spring plus liquid feeds through summer works well. 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 key lime?

What does over-feeding key lime 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 key lime 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 key lime?