Desert Notes: Hanging Gardens

Robin Patten, April 2022

Sheltered in their alcove habitat, maidenhair ferns began unfurling new fronds around the same time the Say’s phoebes started calling and sandhill cranes sang their way across Cottonwood Wash. At least that was the first green that I saw.

On a warm February day, I walked up to the edge of the shallow alcove, expecting to find only the decay of last year’s growth clinging to the rock. The anticipated mass of dead leaves and plant detritus was there, drooping over a moist black ooze, but amidst that brown were the beginnings of vibrant spring growth – the maidenhair fern, other green sprouts, and most delightful of all, a single flowering primrose with its long stem stretching blossoms towards the light, its roots tapping the water that seeped from the rock itself.

I watched with fascination as this desert water source emerged from the rock, slipping out through the plant mass, sliding down old stems to the tips of dead leaves where the drops hung for a glittering moment before falling to the black algae below. The seep is a fount of moisture for plant and animal alike, nurturing the hanging garden tucked into this alcove shelter.

Hanging gardens decorate numerous alcoves in southern Utah deserts, slips of habitat filled with ferns, moss, algae, and a host of flowering plants. But not all alcoves flourish with life; it requires a certain situation of rock and water, geology and aspect, to create conditions where gardens can grow. The moisture comes from above, groundwater soaking down through a permeable layer of rock, flowing through porous stone and cracks over years of time until it hits a resistant layer that forces the water to move laterally. The seeps occur at the exposed line between porous and impermeable rock layers, the water emerging into daylight to create green abundance within the desert.

Around Bluff, the Bluff Sandstone provides that porous overlay, while in other parts of southern Utah, the Navajo Sandstone allows moisture to filter downward. Along the base of the Bluff Sandstone hanging gardens were once so prevalent, a 1938 USGS report dubbed it the “zone of seeps…marked by a band of green vegetation formed by plant species that seem out of place in the present scheme of distribution.”[1] But what we see today along this “zone of seeps” may only be a fraction of the gardens that once existed, for a later 2010 paper notes many of those seeps have dried up.[2]

Yet still these desert oases exist in numbers, spread across the region. The hanging gardens of the Colorado Plateau are diverse, for no one species dominates its alcoves, nor is any one species found in all of the gardens; each is an association developed for that place in this time. Unique species thrive in this habitat, an estimated 25 endemic species – plants found only on the Colorado Plateau – are associated with hanging gardens. ^[3] There are ferns that look like they should be clinging to a rock wall in Scotland and flowers that appear more appropriate for an English country garden, like the alcove columbine (Aquilegia micrantha) and Eastwood’s Monkey Flower (Mimulus eastwoodiae), named for Alice Eastwood, the intrepid early-1900 field botanist. And then there is the endemic cave primrose (Primula specuicola), the same flower I found on that February afternoon, a plant of particular significance for the Bluff region. This little lavender-blossomed beauty was discovered near Bluff in 1911, making Bluff its ‘type locality’ – the place the species was first described.

The hanging gardens are a result of an intricate series of events taking place over the eons: ancient desert sand dunes forming then solidifying into sandstone, plants evolving and surviving over the millennia to reside just there in that specific habitat, water moving slowly through the rock, years passing before it reaches the surface. Strands of time and geography of space unite, so that there on that rock wall on a February day, a primrose blooms. Several weeks later, the alcove holds a flourishing garden of flowers. It is a wonder – I can think of no better word for it.

The hanging gardens are fragile. I approach with care, avoid getting too close so as not to disturb any bit of soil accumulated on the edge, and consider that phenomenon before me – an intimate relationship of stone, water, plant, and animal developed over vast time, an ecological marvel and a verdant bit of beauty within Utah’s canyonlands.

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Thanks to Stewart Aitchison for introducing me to the “zone of seeps,” and other wonderful naturalist information.

[1] Gregory, H. E. (1938). The San Juan Country: A Geographic and Geologic Reconnaissance of Southeast Utah. USGS Professional Paper 188

[2] O’Sullivan, R. (2010). The lower and upper contacts of the Upper Jurassic Bluff Sandstone Member of the Morrison Formation in southeastern Utah. In J. E. Fassett, K. E. Zeigler, & V. W. Lueth (Eds.), Geology of the Four Corners Country. Geological Society 61st Annual Fall Field Conference Guidebook.

[3] James, F. F., Stanton, N. L., & Ronald, L. H. (2007). Distribution of hanging garden vegetation: Associations on the Colorado Plateau, USA. Journal of the Botanical Research Institute of Texas, 1(1), 585-607.