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Various botanical differences have been put forward to justify a specific rank for this tree but, according to the Mexican authority Martinez, none is really reliable, though the leaves are on the average shorter than in T. distichum. It is often said to differ from its N. American ally in being evergreen, but even that is not altogether reliable as a specific character, since trees may be leafless for a time in the cooler parts of the country. Differences of a physiological nature are that knees are rarely produced and the different flowering time – towards the end of the year after the rainy season is over.
Distinct species or not, the Mexican cypress is a splendid tree, found, wild or planted, throughout the more elevated parts of Mexico and extending into Guatemala. Its main habitat is along the banks of rivers and mountain streams, but it also occurs away from visible water. Historically it is the senior tree, cultivated since pre-Colombian times in the Vale of Mexico. Legend has it that the fine trees, some 500 in all, that ornament the Chapultepec Park in Mexico City were planted during the reign of the last Aztec ruler, Montezuma II (d. 1520), though they may be older. Remnants of a formal planting at El Contador, northeast of Mexico City, near Texcoco, formed part of the garden of the local Aztec ruler Nezahualcoyotl (Martinez, Las Pinaceas Mexicanas (1963), pp. 196-9). He died about 1472, so the trees must be some 500 years old. The most famous ahuehuete, and perhaps the most frequently measured tree in the world, grows at Sta Maria del Tule, a few miles south of Oaxaca. This has a tight-tape girth of almost 40 yards, and vast ages have been assigned to it. It is not unlikely that it is really the result of the fusion of three distinct trees; even if it grew from a single seedling it is not necessarily more than 1,000 years old. For a note on this tree, with two portraits, see Journ. R.H.S., Vol. 93 (1968), pp. 478-80 and fig. 240-1.