Key lime (Mexican lime) care

Light

Key lime needs sun on the leaves, not just bright ambient room light. Requires 8+ hours of full direct sun for fruiting. The most sun-demanding common lime; insufficient light leads to sparse flowering and thin, pale fruit. Outdoors in a south-facing spot is best; indoors, a very bright window or grow lights are essential. A south or west-facing windowsill in the northern hemisphere is the default; anywhere else, expect the plant to stretch and pale out within a season.

Watering

Outdoor key lime crops want every 5-10 days in summer; every 10-14 days in cooler months. The single best habit is a finger-test before watering — push a finger 3-4 cm into the soil. Damp = wait a day; dust-dry = water deeply at the base of the plant. Key limes are somewhat drought-tolerant once established but fruit size and juice quality improve with regular deep watering. Allow the top 3-4 cm of soil to dry between waterings. Avoid waterlogged roots; container drainage is critical.

Soil and pot

Key lime grows best in sandy, well-drained slightly acidic soil or citrus compost. pH 6.0-7.0. In the ground, sandy loam drains best. In containers, mix citrus compost with up to 30% coarse perlite or grit. Key lime is intolerant of wet feet even for short periods. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Key lime sits happiest at around 50-70% humidity and 13-35°C (55-95°F). Originates in humid tropical conditions but adapts to moderate indoor humidity. In dry heated interiors, occasional misting or a pebble tray helps prevent leaf edge browning and spider mite outbreaks. If you keep the room above 13 year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed key lime sparingly. 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. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on key lime in the Growli community. Each is annotated with the most common cause so you know where to start.

• Frost damage — Key lime is the most cold-sensitive common citrus. Even a brief dip below 2°C can kill new growth and cause significant dieback. Bring containerised plants indoors as soon as temperatures drop in autumn.
• Thorns causing handling injuries — Sharp thorns on branches are normal but can cause scratches when pruning. Wear thick gloves; remove thorns from main scaffold branches if growing as a container specimen.
• Spider mites in dry conditions — Fine webbing on leaf undersides, bronzed foliage. Raise humidity, spray foliage with water, and apply insecticidal soap or neem oil. Key lime is particularly prone in dry heated rooms.

Propagation

Commonly grown from seed (less desirable; long juvenile period) or from semi-hardwood cuttings taken in late summer with rooting hormone. Commercial trees are grafted onto rough lemon or Rangpur rootstock for vigour. Air-layering works well for maintaining varietal characteristics. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Key lime is mildly toxic to pets. ASPCA lists Citrus species as toxic to cats, dogs, and horses due to citrus essential oils (limonene, linalool) and psoralens concentrated in the leaves and rind. Ingestion can cause gastrointestinal upset, lethargy, and photosensitivity. The juice and flesh at minor doses carry lower risk but are not considered safe for pets. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Key lime deep-dive guides

Every aspect of key lime care, each with its own calibrated guide:

• Key lime watering schedule
• Key lime light requirements
• Best soil mix for key lime
• Key lime fertilizing guide
• When to repot key lime
• How to propagate key lime
• Key lime growth rate & size
• Key lime cold hardiness
• Key lime temperature & humidity
• Is key lime toxic to cats & dogs?
• Is key lime toxic to cats?
• Is key lime toxic to dogs?

Featured in these plant shortlists

Key lime qualifies for 1 curated Growli shortlist — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• Best fragrant houseplants — Indoor plants with scented flowers or aromatic foliage — greenery you can smell, selected from our care library.
• Browse all 29 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Key lime is also known as Key lime, Mexican lime, West Indian lime, and Bartender's lime.

• Regent Grape care — light, water and common problems
• Pink Lemonade Blueberry care — light, water and common problems
• Patriot Blueberry care — light, water and common problems
• All 6887 plant care guides in the Growli library