Key Lime originated in the tropical regions of Southeast Asia — Malaysia and Indonesia most likely — and spread across tropical cultivation by way of trade routes before anyone thought to write it down. It arrived in the Florida Keys in the nineteenth century and became commercial there for a time, though production has largely moved elsewhere. The tree itself is a large shrub or small tree, evergreen, growing 6 to 13 feet, with glossy elliptical leaves that resemble those of the orange tree closely enough to earn the species name aurantiifolia, meaning orange-leaved. Small thorns line the branches. The flowers, fragrant and pale, appear mainly in fall and perfume a warm evening with something close to incandescence.

Key Lime is a plant for genuinely warm gardens: zones 9 to 11, full sun, well-drained light to medium soil, and protection from cold wind. It tolerates drought once established but will not survive standing water or heavy clay. In cooler climates it performs well in a large container moved indoors before frost, though fruit production diminishes without real heat and sun. The thin-skinned green fruits are more aromatic and more intensely sour than the Persian limes of the grocery store — the difference is worth experiencing. Fertilize sparingly, prune only to shape or remove dead wood, and site it with genuine warmth in mind from the start.