Earth Notes: Hanging Gardens

Apr 11, 2018

Hidden within the ocher and vermilion canyons of the Colorado Plateau are lush green edens called hanging gardens. They harbor some of the region’s rarest plants and flowers that exist only in the special zone where water emerges from stone. 

Hanging garden, Zion National Park
Credit NPS/Pete Sawtell

When rain and snow bless the high mesas, the water seeps into porous stone and filters down until it comes into contact with an impermeable rock layer—often where sandstone meets shale. The water then flows sideways until it reaches a cliff or canyon wall—emerging in slow drips and trickles, or as a gushing waterfall.

Over eons, water and wind erode hollows in the cliff faces around these springs. Seeds blow in on the wind, setting the stage for a hanging garden.

The plant communities are pristine because they’re often inaccessible to humans and grazing animals.  Hanging gardens help scientists understand impacts on delicate ecosystems—and they offer a tantalizing look into past ice ages and even more tropical times when these kinds of plants were more widespread.

As climate warmed at the end of the ice ages, many plant species were pushed high into the mountains—but some survived in the moist microclimates and evolved and adapted in the shelter of hanging gardens. Kachina daisy, Zion shooting star, alcove bog-orchid, Eastwood’s monkeyflower, maidenhair ferns—along with mosses, algae, and diatoms. Several of these are found nowhere else in the world.