Mesa Verde—A Garden of Ghosts, Fire and Yuccas

MesaVerdecliffpalace174Each year, thousands of visitors arrive at Mesa Verde National Park to peer into ancient cliff dwellings and puzzle over why and how people once built cities nestled in canyons. An initial glimpse will elicit gasps from those who catch their first view of Spruce House. But Mesa Verde, with 52,074 acres, is a wilderness garden, too. Fires have scorched acre after acre, imparting a ghostly appearance that matches the emptiness of echoes in the dwellings. In moments of quiet, only the wind blows and the mesa appears mysterious and haunted.

MesaVerderabbitbrush120Mesa Verde rolls mile after mile with uncharacteristic greenery after plentiful spring rains. Mariposa lilies push through the soil; their delicate markings on white petals seemingly too fragile for such rugged surroundings. Lightening storms strike with ferocity, more powerful here in Montezuma County than nearly any county of the nation. By late summer the weather mellows–dry and clear with cool nights and hot days. The soil is parched but blooming with bee-covered yellow rabbitbrush and purple tansy asters.

In the Four Corners, a dry spring or even a spring with scant rainfall indicates drought. And drought carries a long history here. By the year 1300 drought perhaps drove these early dwellers to greener pastures and continues to determine the daily life of those who live here or visit. And nothing is more sensitive to drought than the plants hugging the mesas.

MesaVerdejuniperpath146“The east side receives more moisture,” says Marilyn Collyer, supervisor of biological technicians at Mesa Verde, “the west side is hotter and drier. The cooler and wetter weather travels south to north up the mesa.” On the west side, you’ll find forests of pinyon pines and Utah junipers.

Pinyon pines are small and sturdy with edible pine nuts in the cones. The Utah juniper is clothed in ragged bark. Like abstract sculpture, the stark, twisting juniper trunks stand out against the sky. Only a puff of green scales could be called leaves. Bony limbs point to the stars at night and birds sit on the wooden fingers by day. Despite their contrasts, pinyon and juniper live in concert, each allowing the other plenty of space. Ancient Americans used both pinyon and juniper to build roof beams but only the pinyon can be relied upon to reveal a date. The junipers are too twisted to offer scientists core samples.

Walk through the Mesa Verde National Park Museum and you’ll see displays of corn, cotton, squash, beans and amaranth as examples of ancient crops. A wild potato grows here, too, that is small, white and edible. But no plant was more useful to these early people than the yucca, which dominates the mesas today—tough and spiky in an arid landscape.

MesaVerdeyucca143The banana yucca, Yucca baccata, flowers in the spring with a tall spire of waxy white flowers. By the end of summer, curly fibers unravel from the leaves as if to show off their role in early human history. The Ancient Puebloans stripped the fibers of the yucca for twining ropes and weaving sandals. On display in the museum is a single leaf of yucca beaten until shredded, yielding fine strong fibers suitable for woven fabrics or knotted ropes. Without domestic beasts of burden or the wheel, ropes must have played an essential role in hoisting food, lumber and other staples into and out of the cliff dwellings.

The yucca is from the Agave family, which is a subset of a large lily-like collection of plant families called monocots. With over 200 known agave species, perhaps the best known is the Mexican blue agave that produces tequila. Depending on the species, it may take anywhere from four to 40 years for the rosette to produce a stalk of flowers. The rosette then dies.

Asparagus, onions and garlic fall into these subsets, too, as well as the typical garden-variety lilies of beauty and stature. Peer into the spire of yucca flowers and you’ll see a lily appearance. With the ample bulbous roots of all these plants, it’s not too hard to imagine kinship. But lilies are among the most tender and graceful of flowering plants, while many agaves have adapted to arid climates with protective leaves.

Marilyn recently completed a study of Yucca baccata in the Park and found they grow best on a south-facing slope with good drainage. Most flourish as high as 8,000 feet in altitude. Nestled among the pinyon pine and Utah juniper, they will grow, but not as well. “Too much shade,” she reasons, “and not the right soil.”

Yucca root provided a soapy lather for the Ancestral Puebloans. It also provided an edible fruit and remains important for wildlife. By the end of summer, “it’s sweet with the texture of a date,” Marilyn says. Coyotes paw and scrape the flesh; pinyon jays feast on the seeds.

But the most notable relationship the yucca fosters is with a moth. The moth that pollinates the yucca bores into the ovary of the plant and deposits pollen as protein to feed the moth larvae, which will hatch from the eggs of the moth. Without this moth, the yucca cannot be pollinated, although it can send out rootlets to form colonies. “Seeds are needed to get some distance from the plant,” Marilyn explains. Animals eat the yucca seeds, which deposits and spreads seeds widely on accommodating soil.

MesaVerdeburnedforest087If you visit Mesa Verde, much of the top mesa is burned. At first the charred landscape is shocking. If the fire has burned at high temperatures for days, the soil may become glazed, like the pottery shards found among the ruins. Rain no longer penetrates the soil but nutrient-rich silt runs off elsewhere. For scientists, it’s a chance to see how nature rebounds, or suffers, from a large fire. The pinyon pines and junipers disappear, at least for many years, as does the sagebrush and antelope bitterbrush.

“It’s the little stuff that re-sprouts; the undergrowth is much like it was before the fire,” Marilyn says. Gambel oak, serviceberry, fendler bush, mountain mahogany, chokecherry–Marilyn defines this collection as the mountain shrub complex. They return with vigor, robust from the nitrogen, phosphorus and potassium deposited from the ash of the fire. With rain in the spring, she says, “it’s dramatic to see the amount of foliage, berries and seeds that will appear after a fire.” This is what many ancient people across the globe have noticed and reprised as a slash-and-burn method when they cleared fields for a first planting. Wild animals, too, return to reap the abundance after a fire.

MesaVerdeshrubs073Pioneering grasses like squirrel tails and rice grass return, although not the commonly seen mutton grass. In the bottom of the canyon, where the rich ash accumulates, purslane, lamb’s quarters, ground cherry and wild potatoes grow. “The potatoes are no bigger than the tip of your little finger,” Marilyn says, “but you could get about 15 potatoes from each plant.” The soil is sandier, the air more humid and the ground is warmer than above on the mesa.

But the canyon has no water. Unlike many Colorado canyons, no river runs through this canyon and that may be why drought had dire implications for those who tried to live here. Instead, nearly every cliff dwelling is located at the site of a spring, with the dripping of water obvious. Water percolates through layers of sandstone into a shallow pool. At Oak Tree House, which was opened only for the centennial of the Park, the spring shelters a southern maidenhair fern, which cascades down the wet wall in a tangle of dainty foliage. It thrives in the overhang, dependent on a constant supply of clean water, a marvel for anyone to see in this desert climate. Seeds blew in and found an unexpected hospitality in this shady nook.

At Balcony House a ghostly imprint of a hand on one wall indicates that this is a place for water. That hand, the ranger tells visitors, is found wherever there is water at Mesa Verde. Water was precious then, as it is today. Where did these people go? A few stayed behind, but most archeologists today believe the Mesa Verde residents packed what they could on their backs and took their families to kin who lived elsewhere, perhaps along rivers where water was more plentiful and predictable, where corn, beans and gourds could be raised easily.

MesaVerdegourd217In a small courtyard of the main visitors center a garden of corn, beans, rambling squash vines and amaranth grow in a crowded space. It’s more decorative than useful, but serves as an attempt to demonstrate what these early crops might have looked like.

The corn is high with small ears of varicolored kernels. The squash is a gourd with trailing vines crawling up a small tree. Beans are ripening in the pods nearly ready for harvest. Each of these crops could be stored for winter: the corn ground into meal, the beans removed from tough pods and the gourds once ripened with thick skins, stored in dark alcoves. Early people also hunted deer for meat, but kept dogs and turkeys probably as pets.

Agrarian life has disappeared and no crops have reverted to the wild. They require too much fertilizer and water to survive without human care. There’s no sign of wild dogs, either, although there are plenty of coyotes. Turkeys hide among the Gambel oaks, feasting on the acorns. It’s surprising that so much food exists for wildlife in a land too parched for humans. Acorns, berries, nuts and fruits for birds and mammals—a plentiful supply of rabbits for birds of prey—thousands of acres are paradise for others on the food chain.

Now the blight in this paradise is invasive weeds that take advantage of disturbed soil. Musk thistle is one. Marilyn rattles off a list that includes cheat grass. Most of the problem is on Chapin Mesa, where heavy foot traffic may expose soil to weed seeds. Farther away from the high traffic areas, the original shrubs, wildflowers and grasses can hold their own, carrying on the timeless rotation of post-fire recovery. But it may take 50 years for the forest to return with mature trees taking over the mesa. In the meantime, the mesa is flush with bloom. And, as several rangers point out, appears closer to what Mesa Verde must have looked like hundreds of years ago when the first residents called it home.