People call this ancient, 200-foot-tall redwood Grandfather. It’s on private land, deep in the mountains of Santa Cruz, California. The land’s previous owner had planned to cut it down and was only stopped by threat of a lawsuit. Once a year, the current owner, Stanley Acton, allows Tim Kovar to bring people to visit Grandfather, which is somewhere between 700 and 1,000 years old. We’re going to climb it.

 Kovar, who runs a school called Tree Climbing Planet, has already rigged the tree. He shot a fishing line over a high, sturdy branch with a crossbow, then used the fishing line to pull up progressively stronger lines. In the end, two 600-foot ropes looped down to the ground and up again, each creating three climbing stations. Kovar is at one; redwood biologist and tree-climbing veteran Cameron Williams is at another. The last four spots are taken by me and three other newbies, our hearts pounding as we prepare to pull ourselves up, on ropes no thicker than my finger, to the place where tree and sky meet.

 I lift my feet from the ground, surrendering my weight to the rope, and tuck my feet into rope stirrups. Now I am suspended in a padded, green tree-climbing saddle, which is attached by carabiner to the rope stretching up above my head. The stirrups are attached to a climbing device called an ascender. As I slide it up the rope, it pulls my knees to my chest. Then I stand up and slide a second ascender up the rope over my head. I am now a foot higher than where I started. Time to do it again. Knees to chest. Stand and slide.

The author high among Grandfather's branches | Photo courtesy of Dashka Slater

 As I inchworm my way up, the awkward motion soon becomes easier. The massive red trunk slides past, creviced and shaggy, splotched with lichen. Before long, we are threading ourselves between the first of the sturdy original branches, those that formed sometime during the reign of Kublai Khan.

 Now the world of trees begins to reveal itself. Directly across from me is another redwood, its bark pocked with hundreds of circular holes made by woodpeckers to stow acorns. Above me is a neat, flat cut where the previous property owner lopped off one of three enormous, view-blocking limbs. The top of the chainsaw cut is already being swallowed by a flow of cambium, the living tissue of the tree. This is how redwoods heal, Williams explains—the cambium oozes like lava over the wound, keeping out the oxygen that could cause decay. Eventually, all traces of the cut will disappear.

 We are nearly 100 feet off the ground now, high enough to discover other secrets: an abandoned squirrel nest, made from flat redwood needles, twigs, and shredded bark; a burl shaped like an ear and pierced with sapsucker holes; limbs festooned with whorls of green lichen. We encounter a limb that has grown vertically, rather than horizontally, to fill a light gap. To support the weight of this L-shaped branch, the tree has filled the space between limb and trunk with 30 to 40 inches of dense wood—a buttress. This is how the tree fills in its crown while ascending higher into the foggy heights.

The view west toward Santa Cruz. | Photo courtesy of Dashka Slater

 I am high enough to see across the mountains now, my gaze skittering over the green ridges. Feathery branches whisk the air. Above me is the top of my rope, knotted to a branch. Above that is the sky. A breeze sighs past, stirring the tree’s perfume of spice and loam.

 Time stops, or slows to redwood pace, which is almost the same thing. It doesn’t matter if I go higher, or if I ever come down.

 But Kovar reminds us that we belong on the ground, and that it will be easier to get there in daylight. Reluctantly, I rappel down in long swoops, like a spider lowering itself from the ceiling. When my sneakers land in the soft duff, my legs feel wobbly and ill-fitting. Gravity is too heavy, the ground too dense and close.

 Small and earthbound, I climb into my car to return home. For an afternoon, I have been arboreal, standing on the shoulders of a forest giant.