Key lime

Sun

Full sun, ideally at least 6-8 hours daily; shelter from cold and drying winds.

Water

Water deeply, then let the surface soil begin to dry before watering again. Containers need regular checks in summer and much less water during cool winter conditions.

Soil

Well-drained soil or a free-draining citrus potting mix, preferably slightly acidic. Avoid waterlogged ground and pots standing in water.

Height

6-15 ft (1.8-4.6 m); usually smaller in containers

Spread

6-12 ft (1.8-3.7 m)

Flowers

Fragrant white flowers, sometimes pink-tinged in bud, mainly in spring with further flushes in warm weather.

Foliage

Evergreen. Small, glossy green, oval leaves with a citrus scent when crushed; branches commonly carry sharp thorns.

Growth

Moderate in warm conditions; slow in cool climates.

Care needed

Medium

• Pollinators
• Heat tolerant
• Low allergen
• Fragrant
• Edible

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Hard

Toughness

Needs looking after

Pick your zone, country, light and whether you have pets.

1. Planting day

   7 ft (2 m)

2. After 1 year

   7 ft (2 m)

3. After 2 years

   7 ft (2.1 m)

4. After 3 years

   7 ft (2.1 m)

5. After 5 years

   7 ft (2.2 m)

About 26 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Toxic

Growth rate

Slow

• Keep the root flare above soil level and the graft union, if present, clear of soil and mulch.
• Water the root zone thoroughly without leaving it constantly wet.
• Feed during active growth with a citrus fertiliser containing trace elements, following the label; do not feed a cold, dormant plant.
• Mulch outdoor trees, leaving a clear gap around the trunk.
• Move containers into bright, frost-free shelter before cold weather, and return them outdoors gradually once nights are reliably warm.

Pruning. Prune lightly in spring once frost risk has passed, removing dead, damaged and crossing branches. Remove shoots below the graft union whenever they appear, and avoid hard pruning, which removes flowering and fruiting wood.

Pick full-sized limes, usually 3–5 cm across, when heavy for their size and green turning yellow; fully yellow fruit is also ripe, and clipping the stalk avoids tearing the skin. Fruit generally ripens 4–6 months after flowering, potentially year-round in tropical parts of the US and Australia; in the UK and most of Canada, reliable cropping needs a warm, bright greenhouse or conservatory.

Late winter

Check sheltered plants for scale insects and spider mites; keep watering restrained but do not let the root ball dry out completely.

Spring

Prune lightly after frost risk has passed and begin feeding as active growth resumes.

Late spring

Acclimatise overwintered containers to outdoor sun gradually once nights are reliably warm.

Summer

Check container moisture frequently and water thoroughly when the surface begins to dry.

Autumn

Move containers into bright shelter before cold nights arrive; inspect foliage for pests first.

Year-round

In warm climates, harvest fruit as it reaches full size; yellow fruit is fully ripe. Use seasonal tasks according to your local hemisphere.

• Use a large container on a sunny terrace so the tree can be moved into winter shelter.
• Plant near an outdoor dining area for fragrant flowers and readily accessible fruit, keeping thorny branches away from seats and paths.
• Include in a frost-free kitchen garden or small citrus orchard.
• Use as a glossy evergreen focal point in a sheltered courtyard, with low planting kept clear of its trunk.

Garden styles it suits: Modern courtyard, Mediterranean, Tropical, Potager (kitchen garden), Edible landscape and Backyard orchard.

Plant it with: Basil, Thyme, Oregano, Sweet alyssum and French marigold.

Wildlife: Flowers provide nectar and pollen for bees and other insects. Container plants indoors may need gentle hand-pollination if fruit set is poor.

• Scale insects and mealybugs: inspect stems and leaf undersides, wipe off small infestations and use a citrus-labelled horticultural oil if needed; avoid spraying in hot sun.
• Spider mites: watch for fine webbing and pale stippling, especially indoors; rinse foliage regularly and use a labelled treatment if the infestation persists.
• Root rot and yellowing from waterlogging: improve drainage, empty saucers and let the surface dry slightly between waterings; do not assume yellow leaves always need more fertiliser.
• Citrus greening disease: blotchy, uneven leaf yellowing and small, misshapen fruit need assessment in affected regions. There is no cure; contact your local plant-health authority and follow rules on citrus movement and removal.

The edible flesh and juice are not normally toxic to people. Juice or peel oils on skin followed by sunlight can cause severe blistering, so wash splashes off promptly. Leaves, peel and concentrated citrus oils can poison cats and dogs if eaten, causing digestive upset and sometimes skin irritation; keep them away from prunings and oils. Horse-specific toxicity information is limited, so do not offer foliage, peel or oils as feed. Thorns can cause puncture wounds.

• Persian lime (Citrus × latifolia)

  Usually has larger, more oval fruit with few or no seeds, larger leaves and fewer thorns; Key lime fruit is smaller, rounder and commonly seedy.

• Makrut lime (Citrus hystrix)

  Has conspicuously double-looking leaves formed by a broad winged leaf stalk, and rough, deeply bumpy fruit; Key lime leaves have much narrower wings and its fruit is comparatively smooth.

• Lemon (Citrus × limon)

  Usually bears larger, elongated fruit with a pronounced nipple at the tip; Key lime fruit is smaller and rounder. Colour alone is unreliable because ripe Key limes also turn yellow.

Key lime takes its common name from its long association with the Florida Keys, while aurantiifolia means orange-leaved.

Propagation. Seed can be used, but seedlings take several years to fruit and results are not guaranteed. Budding or grafting onto a locally suitable citrus rootstock is the usual way to obtain a predictable garden tree; buy certified disease-free stock and observe local citrus movement restrictions.

Accepted botanical name

Citrus aurantiifolia

Sources: GBIF (CC BY 4.0). The care and design notes are LandscapeGPT's own.