Amsterdam in 1638 was a city of disease. Plague returned every few years. Cholera moved through the canal-borne summer. The treatments were herbal - tinctures of foxglove for the heart, willow bark for fever, opium for almost anything that hurt. The City Council founded the Hortus Medicus that year to give physicians and pharmacists somewhere to learn the plants they prescribed. Students walked the beds with their teachers, identified each species, took their exams between the rows. The garden was a teaching tool first and a curiosity second - though for the wealthy merchants who funded it, the line between the two was always blurry. Plants from the New World arrived in the same ships that carried sugar and silver, and the Hortus accepted what arrived.

The Dutch East India Company changed what could grow in Amsterdam. Through the seventeenth century its ships brought back plants and seeds from Java, Sri Lanka, the Cape of Good Hope, and the Mascarene Islands - some for medicine, some for trade, some because a captain thought a curator might want them. A single coffee plant, brought back from Mocha in Yemen via Java, ended up in the Hortus around 1706. It survived. The Dutch had been the first Europeans outside the Ottoman world to cultivate coffee, and Amsterdam now held the genetic raw material for an industry that did not yet exist west of the Atlantic. A cutting eventually travelled to Paris and then to French and Dutch Caribbean plantations. From there it crossed into Brazil. The whole vast Latin American coffee economy descends from that lineage. Two small potted oil palms that arrived from Mauritius around the same period produced seeds that became the founding stock of Southeast Asian palm plantations in the Dutch East Indies. The garden was, in retrospect, a node in a botanical empire.

By the 1880s the Hortus had reinvented itself as a research garden. Hugo de Vries became director in 1885 and held the post until 1918, doing some of the most important plant genetics work of the late nineteenth century from a desk inside the garden. He rediscovered Mendel's laws of inheritance independently, around the same time that Carl Correns in Germany and Erich von Tschermak in Austria did the same. De Vries also formulated his mutation theory of evolution - the idea that new species could arise through sudden heritable changes rather than gradual selection. The theory had problems, but the work made the Hortus internationally famous in scientific circles. To keep de Vries from leaving for a richer position elsewhere, the garden's board built him a new Palm House and laboratory. The Palm House still stands.

In 1987 the Hortus nearly died. The University of Amsterdam, which had supported the garden for over a century, stopped paying its bills. The garden had three months of operating funds, an aging hothouse, and a payroll for a small staff of gardeners and curators. What saved it was the city's affection. A community of supporters - the Friends of the Hortus - mobilized donations, lobbied the City Council, and kept the gates open through the worst of the crisis. The Council eventually picked up the slack the university had dropped, and the Hortus has been city-supported ever since. The lesson the survival taught is one the place wears comfortably now: a botanical garden is a slow asset. Its plants do not get more valuable in a quarterly report. It must be paid for because someone, somewhere, cares.

Today the Hortus presses up against the Plantage district's quiet streets, a green pocket between the Artis Zoo and the canals of central Amsterdam. The Palm House holds tropical and subtropical species in three different climate zones. A Persian ironwood - Parrotia persica - grows in the open garden, its bark flaking in patches of grey, green, and rust. The Victoria water lily blooms in summer in a heated pond, its leaves wide enough to support a small child if you were foolish enough to try. The garden runs cafés, lecture halls, and conference space now alongside the science. The collection includes some of the oldest cultivated plants in Europe, descendants of seeds and cuttings that arrived in Amsterdam when the Republic still ruled the spice trade. Every cup of coffee in the Hortus café is, in a small genealogical sense, a homecoming.