Читать книгу The Trees of San Francisco онлайн

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LOCATION: 1011 S. Van Ness Ave./21st St. in the Mission; also at 438 Arkansas St. in Potrero Hill

Avocados were introduced to Florida in the 1830s, but not until the 20th century did the avocado industry really take off in the United States, in California. Carl Schmidt, a 21-year-old employee of a nursery in Altadena, California, was sent to Mexico in 1911 to search for the country’s best avocados and bring back cuttings of the trees from which they came. On his return, many cuttings refused to adapt to California’s soil and cooler climate, but one flourished; when it survived the great freeze of 1913, it was given the name fuerte, the Spanish word for “strong.” This tree is credited with starting California’s avocado industry. The famous ‘Hass’ variety (95% of the California crop) originated in 1935 when Rudolph Hass, a postman and amateur farmer in La Habra, California, discovered a superior tree in his 2-acre orchard. (The tree can still be seen in La Habra.)

Avocado flowers are cross-pollinated, meaning that flowers of one tree can be pollinated only by pollen from another tree—a botanical trick that encourages genetic diversity. Cross-pollination is actually achieved by the stigma (the female part of the flower) becoming receptive to male flowers’ pollen before the pollen is released from flowers of the same tree. (This is one reason that avocado trees rarely set fruit in San Francisco—not enough other avocados are nearby!) The large seed of the avocado is an adaptation for supplying young plants with enough food to enable them to survive in the dark forest undergrowth until they can attract sufficient light to survive.