In the last week of April in 1685, in the middle of a raging naval war, the English explorer and naturalist William Dampier arrived on a small island in the Bay of Panama carpeted with claylike yellow soil. Dampier — the first person to circumnavigate the globe thrice, inspiring others as different as Cook and Darwin — made careful note of local tree species everywhere he traveled, but none fascinated him more than what he encountered for the first time on this tiny island.

Dampier described the black bark and smooth oval leaves of the tall “Avogato Pear-tree,” then paused at its unusual fruit — “as big as a large Lemon,” green until ripe and then “a little yellowish,” with green flesh “as soft as Butter” and no distinct flavor of its own, enveloping “a stone as big as a Horse-Plumb.” He described how the fruit are eaten — two or three days after picking, with the rind peeled — and their most common local preparation: with a pinch of salt and a roasted plantain, so that “a Man that’s hungry, may make a good meal of it”; there was also uncommonly delectable sweet variation: “mixt with Sugar and Lime-juice, and beaten together in a Plate.” And then he added:

It is reported that this Fruit provokes to Lust, and therefore is said to be much esteemed by the Spaniards.

Avocado by Étienne Denisse from the stunningly illustrated 19th-century French encyclopedia Flore d’Amérique. (Available as a print, a cutting board, and stationery cards, benefitting the New York Botanical Garden.)

But far more fascinating than the cultural lore of the avocado are its own amorous propensities, uncovered in the centuries since by sciences that would have then seemed like magic, or heresy.

The most nutritious known fruit, the avocado — a mostly evergreen member of the laurel family — is a ghost of evolution that should have grown extinct when the animals that fed on it and disseminated its enormous seeds did. Mercifully, it did not. Ample in Europe and North American during the Ice Age, it somehow managed to survive in Mexico and spread from there. But even more impressively, it managed to survive its own self-defeating sexual relations — the botanical equivalent of the human wire-crossing Eric Berne described in his revelatory 1964 classic Games People Play.

Bald of petals though the tree’s small greenish blossoms may be, they are an example of “perfect flowers” — the botanical term for bisexual blooming plants, which can typically self-pollinate. The avocado, however, is far from reproductively self-sufficient due to an astonishing internal clock, which comes in two mirror-image varieties.

In some cultivars — like the Hass, Pinkerton, and Reed avocados — the blossoms open up into reproductive receptivity in their female guise each morning, then close by that afternoon; the following afternoon, they open in their male guise. Other cultivars — the Fuerte, Zutano, and Bacon avocado among them — bloom on the opposite schedule: female in the afternoon, male by morning.

Thisbe by John William Waterhouse, 1909. (Available as a print.)

This presents a Pyramus and Thisbe problem across the wall of time — while both partners inhabit the space of a single tree, they can’t reach each other across the day-parts and need to be pollinated by trees on the opposite schedule. Their reproduction is further derailed by the fact that some varieties, like the Hass, only fertilize to fruition every other year.

Ever since humans have cultivated Earth’s most nutritious fruit, they have tried to help the helpless romancer with various intervention strategies — grafting, planting trees with opposite blooming schedules near each other, even manually pollinating blossoms of the same tree.

The world’s most beloved avocado — the Hass — is the consequence of human interference consecrated by happenstance in the hands of a California mailman in the 1920s.

The Hass avocado in Northern California. (Photograph: Maria Popova.)

The year he turned thirty, Rudolph Hass (June 5, 1892–October 24, 1952) was leafing through a magazine when an illustration stopped him up short: a tree growing dollar bills instead of fruit. He was making 25 cents an hour delivering mail while raising a growing family. The tree, he learned, was an avocado and its fruit were promised to be the next great horticultural boon.

Rudolph took all the money he had, borrowed some from his sister Ida, and bought a small grove of the leading commercial avocado variety — the Fuerte — with a few other cultivars sprinkled in. Needing the greatest possible gain from his grove, he wanted only Fuertes but couldn’t afford to buy any new trees. Instead, he decided to cut down some of the old ones and graft them to become more fertile young Fuertes. He took counsel from a professional grafter, who said the best technique was to graft with his own seedlings. He had none. But it happened that a man on his mail route had a mighty green thumb and was experimenting with growing avocados from seeds, which he got from restaurant refuse.

Rudolph bought three of the lustrous dark orbs and planted them in his grove. They sprouted. When they grew strong enough, he grafted onto one of them a cutting from one of the mature Fuerte trees. The graft didn’t take. He tried again on another of the seedlings. This too failed.

Resigned, Rudolph abandoned the experiment and let his surviving seedling grow as it pleased. In a neglected corner of the grove, it quietly went on doing what trees, those masters of improvisation, do — press on with their blind optimism. When it reached maturity, it began bearing fruit that looked nothing like any other avocado — dark and luscious, the Braille of its skin glimmering with violet.

When Rudolph cut one open for his five young children, they declared those were the most delicious avocados they had ever tasted.

Soon, the world would agree.

This being America and that being the wake of the Great Depression, the Hass family had patented the avocado within a decade.

Rudolph and Elizabeth Hass in front of the mother tree

After describing his “new and improved variety of avocado which has certain characteristics that are highly desirable” and listing all the ways in which “the present invention” differed from existing avocados — higher oil content, superior flavor, doesn’t drop from the tree or rot inside before ripening, resists cold blasts, and, oh, it is almost purple — Rudolph ended his patent application with a summation of his creation that hums with a kind of humble pride:

I claim as my invention: The variety of avocado tree… characterized by its summer ripening, medium-sized fruits, of purple color having a leathery skin… and borne on long stemps [sic], with a small tight seed and with creamy flesh of excellent color and nutty flavor, smooth with no fibre and butter-like consistency.

Rudolph Hass’s avocado patent, 1935.

In the near-century since Rudolph’s hopeful and hapless experiment, the Hass avocado has begun bringing in more than a billion dollars a year for growers, accounting for four fifths of the American avocado industry. But Rudolph Hass continued working as a mailman until he was felled by a heart attack months after his sixtieth birthday, months before Rachel Carson indicted her country with the reminder that “the real wealth of the Nation lies in the resources of the earth — soil, water, forests, minerals, and wildlife.”

Today, every single Hass avocado in every neighborhood market that ever was and ever will be can be traced to a single mother tree grown by a destitute California mailman in 1926 — tender evidence that every tree is in some sense immortal, and a living testament to how chance and choice converge to shape our lives.