Almost 40 years ago the poet W.S. Merwin bought 3 acres of ruined land on the north coast of Maui. By the state’s assessment it was a “wasteland” after a century of deforestation, cattle grazing and a failed attempt at growing pineapple. Today that “wasteland” has grown into a 19-acre palm garden, a sanctuary for 800 species, many of them rare and endangered, now protected by the nonprofit Merwin Conservancy.

“What Is a Garden?” is a luminous collection of photographs by Larry Cameron and essays and poems by Merwin that attest to this astonishing transformation.

The title asks a seemingly simple question: “What is a garden?” But the response is as complex as the land itself. Merwin muses in the essay “The House and Garden” that the very idea of a garden has reversed from its origin. Originally designed to keep the wilderness out, gardens now serve “to keep encroaching human exploitation and disturbance out.”

In the essay “Coming to Palms,” Merwin acknowledges the paradox of the garden: “A plant in the garden is at once the natural world itself and an object of human arrangement.” These essays gracefully reference the god Kanaloa, Swedish botanist Carl Linnaeus, medieval Japanese garden designer Muso and more.

The eight poems are classic Merwin: unpunctuated, sinuous and elemental. A garden is full of water, light and imagination. In the title poem, Merwin writes: “And there I planted young palms in places I had not pondered / until then I imagined their roots setting out in the dark / knowing without knowledge I kept trying to see them standing / in the bend of the valley in a light that would come.”

These poems, including “Rain at Night,” a lament for the original forest, insist on the future — no small feat, considering the depleted soil Merwin and his wife, Paula, nurtured back to life. In the lovely “To Paula in Late Spring,” Merwin, 88, writes, “Let me imagine that we will come again / when we want to and it will be spring / we will be no older than we ever were.”

Merwin had originally wanted to restore the rainforest, but only palms would grow. “The native forest I had hoped to re-create I learned was impossible,” he writes in the introduction. Still, the native forest was the model for the garden, and Cameron’s striking photographs capture the majesty of the palm forest and vibrant life it shelters, from orchids to a toad.

As a whole the introduction and three essays are repetitive. Encountering the same salient details about Merwin’s childhood and his first encounter with the land creates the bewildering effect of wandering through a forest, thinking that surely you must have passed by this tree before. This proves a small distraction, however, in a collection full of wisdom, visual pleasure and sensual, lyrical poems by the former poet laureate who has twice won the Pulitzer Prize.

In the essay “Coming to Palms,” Merwin writes, “But a garden is made of hope, which contributes to its pleasure and its fragility.” Merwin’s garden is certainly made of more than hope. “What Is a Garden?” is a testament to Merwin’s unparalleled poetic and environmental ethos, inseparable from the daily labor in the garden.