WITHIN THE hallowed halls of the National Gallery of Art in Washington, DC, hang priceless masterpieces—works by Vermeer, da Vinci, Morisot, Monet, Rembrandt. Yet one of the museum’s most treasured collections lies not inside its neoclassical walls, but beyond them. Out of the public eye, tucked between the building’s exterior and what the museum’s architect John Russell Pope conceived of as “moat walls,” is something just as enticing: plants nurtured, hand-watered, and meticulously cultivated by a dedicated team. Among them are showy varieties of ficus, aglaonema, and bromeliads for rotunda displays; the museum’s prized azaleas; and—increasingly valuable—a collection of small plants that could easily be mistaken for weeds.
For the last four years, Solomon Foster, the National Gallery’s senior horticulturist and manager of the museum’s 11 greenhouses, has tended to these…
