Trees growing in the rock walls of Zion National Park

I remember being in college the first time I heard about the Hanging Gardens of Babylon, considered by many to be one of the seven wonders of the ancient world. I pictured these mythic gardens as masterpieces of flowers and foliage that were somehow suspended hundreds of feet in the air. According to ancient texts, though, the gardens weren’t hanging in the literal sense, but only appeared to be floating. This was due to a remarkable product of human ingenuity.

THE HANGING GARDENS OF BABYLON

The story goes that King Nebuchadnessar II built the hanging gardens for his homesick wife who found the flat, desert terrain of Mesopotamia depressing.  To please her, he created an artificial mountain out of clay bricks and embellished it with a series of tiered gardens. The unique design featured a mix of exotic plants that cascaded downward, giving the impression that they were suspended in mid air.

Artist’s rendering of the Hanging Gardens of Babylon/Photo: unmuseum.org.

By some accounts, the gardens measured 400′ by 400′ and towered as high as 80′. A stairway led to the uppermost level. Beside the stairway, a series of mechanical screws pumped water from the Euphrates to the top of the garden. From there, the water trickled down to the terraces. Historians estimate the gardens may have required up to 8,200 gallons of water a day to irrigate the plants in this way.

Whether or not the Hanging Gardens of Babylon every existed, I later learned that hanging gardens do flourish in many parts of the world, and just as in Babylon, they often take root in desert environments. Unlike King Nebuchadnessar’s garden masterpiece, however, they are naturally generated and require no help from man. Just the same, they are every bit as grand a feat of landscape engineering.

THE HANGING GARDENS OF ZION NATIONAL PARK

Of the many hanging gardens found around the world, Zion National Park lays claim to some of the most unusual. This is largely due to the rock formations that make up the park. These formations, known in geology as the Navajo Formation, provide the perfect environment for hanging gardens to develop.

Zion’s hanging gardens contain plant communities with a special ability. Unlike their soil-based cousins, they are able to establish themselves in rock. Moreover, the plants seem to thrive in the park’s desert setting, an environment that is normally hostile to their very survival.

Standing on the trail, looking upward, it’s hard to believe there are actual trees growing out of the rock. How is this possible? The secret lies in the sedimentary rock. While by all appearances solid, it is highly porous. As a result, it soaks up rainwater like a sponge, creating unique habitats for water-loving plants to grow.

In fact, the combination of porous sandstone and adjacent levels of impervious (Kaibab) limestone, create the perfect conditions for all kinds of hanging gardens to establish. As water seeps down through the sandstone, it pools in places where it encounters the impenetrable stone. Then, pulled by gravity, it continues its path downward through joints and cracks, while slowly nourishing the plants below.

It’s a lot like a vertical garden.

Water ‘seeps’ can range from small moist patches on stone, to short-lived trickles, to full-fledged gushing streams and finally to pools that weep all year. The most spectacular hanging gardens form where there is constant seep coupled with lots of shade to keep plants lush and moist. This explains why plants such as ferns, wildflowers, grasses and mosses are often found in these well-watered areas.

THE PHENOMENON OF WEEPING ROCK

Zion’s most famous hanging garden is called Weeping Rock. It is reached by a short but steep trail up a rocky hillside. As the path clears the rise, sand and gravel give way to moss and slippery rocks fed by long ribbons of water oozing from a canyon above. The canyon floor is formed of impermeable shale, so it sheds the water down through porous rock until it finally finds a place to penetrate.

What’s unique about Weeping Rock is that the permeable layer has eroded further than the impermeable layer, forming an impassable rock shelf. As a result, water collects on this level before streaming down the sandstone walls and terrace. Eventually, it cascades into a pool below.

Weeping Rock at Zion National Park

Pool where water collects under Weeping Rock

Weeping Rock is best viewed from beneath its natural arch, which features a garland of mosses and ferns. The seeping walls of the crescent-shaped stone terrace are home to lush green vegetation, including wildflowers, ferns, grasses and orchids. All of these plants are growing straight out of the rock. And some are even growing upside down.

The columbine Aquilegia grahamii, is one of many exotic plants found growing in the sandstone. (It’s a wonder since it’s known to grow only in extremely fragile environments.) Needless to say, its brilliant yellow and mango blooms add a colorful touch to the red stone walls.

Aquilegia grahamii columbine

Other beautiful flowers found growing at Weeping Rock include orchids and monkey flowers, to name just a few.

Monkey flower

Orchid and columbine growing out of the rock walls of Zion

For more information on Zion National Park and its hanging gardens, click here for the National Park Service website.