Key/mexican Lime

Key lime trees want full sun and a site shielded from cold winds, since foliage can be damaged near freezing and the best fruit quality comes from the warmest spots available; container plants do well in a well-drained, loose mix cut with perlite or sand. Growers commonly raise seedlings from seed, which come true to type thanks to the tree's polyembryony, though hardwood cuttings, air-layers, and grafting onto locally chosen rootstocks are also used, including rootstocks suited to high-pH, calcareous soils.

Watering is best judged by feel rather than schedule: let the top inch or so of soil dry before watering again, since the tree tolerates neither prolonged drought nor waterlogging. Container specimens benefit from a slow-release fertilizer applied sparingly, and periodic pruning to remove overgrown growth improves airflow and light penetration through the canopy.

Citrus canker, caused by the bacterium Xanthomonas campestris pv. citri, infects leaves, causes defoliation, and blemishes the fruit peel. Citrus greening, or Huanglongbing, caused by Candidatus Liberibacter and spread by the citrus psyllid, invades the tree's phloem, killing sections of canopy and eventually the whole tree. Root and trunk rot from Phytophthora cinnamomi can also affect the tree at the roots.

Fruit is typically picked while still green, since the color most gardeners associate with a ripe lime is really an unripe stage; left on the tree, it turns yellow as it fully matures. At harvest the fruit is small, roughly 1.5 to 2 inches across, with a thin, smooth, leathery peel and 10 to 15 seeds inside a juicy, highly acidic pulp.

Culinary: the juice and zest flavor drinks, especially those built on rum, tenderize raw fish for ceviche, and the dried peel is used as a condiment; the fruit is a daily kitchen staple across many cuisines and is pressed for juice, most famously in Key lime pie.

Medicinal: across its range the fruit has a long folk-medicine record, used in Malaya for headache and stomach ache, in Trinidad for toothache, cystitis, and as a depurative, in Haiti as an antidote to manihot poisoning and for catarrh and diarrhea, in Mexico for biliousness and diarrhea, and in the Bahamas for colds.

Citrus as a genus traces to Southeast Asia, including eastern and northeastern India, northern Burma, southwestern China, and the Malay Archipelago. The Key lime itself is thought to be a tri-hybrid cross of citron, pummelo, and a microcitrus species. Arab traders carried it across North Africa into Spain and Portugal, and Spanish and Portuguese explorers brought it to the Americas in the early sixteenth century, after which it naturalized throughout the Caribbean, the east coast of Mexico, Central America, tropical South America, and the Florida Keys, with commercial planting recorded in Florida by 1883.