In 1867, Simon Schwendener startled the scientific world when he announced to the Swiss Naturalists’ Club that lichens were not the distinct organism they had long been thought to be, but rather were formed of two separate organisms:  a fungus and an alga. Leading lichenologists were outraged at the radical idea; not for 50 years would Schwendener’s theory be accepted. But once it was, lichens were seen as a classic example of a mutually-beneficial symbiosis:  The alga, able to photosynthesize, provides food for the fungus; the fungus provides shelter and water to the alga.

Some 20,000 kinds of this unique association grow on earth, living in almost every environment, from within Antarctic rocks to the surface of desert soils. Lichens can withstand years of desiccation by simply becoming dormant. They revive again with miniscule amounts of water – in the desert, humid night air suffices. While dormant, lichens can also stand searing heat and extreme cold; some species can survive temperatures as high as 180ºF and as low as 100ºF below freezing. Some arctic lichens are estimated to be over 4,000 years old, among the world’s oldest plants.

What looked to early botanists like a single plant is actually a highly-organized association of hundreds to millions of microscopic algal cells woven into a fabric composed of fungal filaments, or hyphae. The fungus forms the thallus, or body of the lichen; the algae, arranged in a thin layer near the top of the thallus, absorb solar energy and produce food.

Lichens come in three different forms. Crustose lichens often form colorful patches on rocks, adhering so tightly to their growing substrate that they cannot be separated. The bodies of fruticose lichens, such as beard lichens hanging in clumps from tree branches, are formed of many slender stalks. Foliose lichens, common on the surface of soils in forests and on tree trunks, get their name from the upcurled edges of their thalli, which resemble drying leaves.

New lichens grow from soredia, specialized pieces of the parent thallus consisting of a few algal cells enveloped by fungal hyphae. Soredia are designed to break away easily with the action of wind or rain. The fungi of some lichens also reproduce by themselves, producing spore which grow into new fungi, or if they encounter a suitable alga, into another lichen.

When Simon Schwendener announced his two-separate-organisms theory, he further asserted that the fungus captured the alga and lived off its food-making ability. New research supports this once-poo-poohed kidnapping theory:  When a fungus finds an alga, it interferes with the algal food-production process, turning the algae into “slaves” that make and secrete food for the fungus; yet the algae do not appear to benefit.

Next time you see a lichen, examine it closely – its life is not as simple as it seems.

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Technorati Tags: plants,plantlife,plant,Creosote bush,desert

My family and I moved to Las Cruces in summer, arriving on the heels of a late-evening thunderstorm. Darkness hid the landscape by the time we drove round the bend on I-25 north of town, but our noses told us where we were. The cool night air pouring in the car windows bore a rich and complicated mix of odors: citrus, sweet nectar, vinyl, camphor – emanating from creosote bush, the fragrance of our new home in the Chihuahuan desert.

Creosote bush is hard to miss in Southern New Mexico – its wiry form and sparse olive-green foliage are often all you see on alluvial fans, mesas and other sandy or gravelly soils. Creosote bush grows throughout the Southwest and northern Mexico.

Although widespread, it is not widely appreciated. Many consider the miles of creosote shrubland boring; others think it worthless, since cattle refuse to eat its resinous foliage; still others object to the fragrance produced when its coating of fifty or more volatile oils is washed off into the air by a desert rain. (In Mexico, its name is hediondilla—little stinker.) Regardless, creosote bush is an integral part of the desert, and a sophisticated example of the strategies plants use to adapt to the harsh environment.

Creosote bush’s distinctive odor and the leaves’ shiny appearance are due to a resinous, varnish-like coating which helps the plant keep from drying out. The sophisticated coating also screens the sun’s harsh rays, sheltering the delicate inner cells from heat and ultraviolet light. And it discourages grazers – the mix of waxes, volatile oils and other compounds tastes terrible and is indigestible to most animals. Only one small grasshopper, which spends its entire life on creosote, happily munches the resinous leaves.

Tasting terrible and smelling funny helps creosote bush survive in the most difficult desert environments, from parts of Baja California where four years may pass without significant rainfall, to the floor of Death Valley, where temperatures sometimes fluctuate 70 degrees from day to night. Not only does it survive, it thrives: the oldest living plant is a 9,000-year-old creosote bush in the Mojave desert of southern California.

Creosote bush’s complex chemical armor contains a veritable medicine chest: Native desert-dwellers drink teas steeped from the fragrant branches and inhale the pungent smoke to treat complaints from colds to fungal infections to rheumatism. Not surprisingly, researchers have found that the resins contain painkillers, fungicides, anti-inflammatories, and a powerful antioxidant which may be useful in treating alcoholism, liver diseases and cancer.

Whenever I breathe creosote-perfumed air after a rain, I remember this creation story told by the Pima and Papago Indians:

When Earthmaker took the first soil from his breast, they say, creosote bush was the first thing to sprout.
From the unpretentious creosote, Earthmaker created the world.

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The majestic soaptree yucca spears the New Mexico sky . Photo by Michael and Allison Goldstein.

Driving Interstate 10 between Deming and Lordsburg, travelers cross mile after mile of high grassy plains punctuated by odd-looking plants the height of a small trees. Growing up to 20 feet tall, the plants look like thick-trunked, short, palm, hence one common name:  palmilla, “little palm.” These grassland “trees” are soaptree yucca, the state flower of New Mexico.

Soaptree yucca is an interesting plant in all seasons. But its flowers are truly spectacular. In late spring and early summer, soaptree yucca sprouts flower stalks up to ten feet tall, laden with clusters of waxy, ivory-colored, bell-shaped blossoms. On moonlit nights, the tall, glowing columns inspire another common name:  “Our Lord’s Candles.”

Soaptree yucca flowers exude a subtle fragrance that attracts nighttime nectar feeders like bats and moths. But like all yucca species, soaptree yucca depends on just one particular pollinator, a yucca moth. The relationship is so specific that different species of yucca moths pollinate different species of yucca. And each depends on the other:  The small, night-flying moths cross-pollinate the flowers, ensuring yucca reproduction; the developing yucca fruit, in turn, nourishes the growing moth larvae. Female yucca moths fly from flower to flower, gathering pollen from one flower, shaping it into a ball, then flying to another flower. They stuff the pollen ball into the second flower and deposit their eggs in its ovary. The growing moth larvae feed on the fruit and seeds, leaving sufficient seeds to produce new yucca plants.

Yucca has long been useful to Southwesterners. People split and chewed the fibrous leaves to make rope, matting, sandals, baskets, and cloth. The leaves also thatched house roofs and shade ramadas. The succulent buds and young flower stalks were prized as a vegetable, and the ripe fruits roasted and dried. The name “soaptree yucca” refers to the gentle soap obtained from the pounded or boiled roots of all yuccas.

Most yucca leaves are stiff, quite waxy, and end in a stout spine, repelling all but the most determined grazers. But soaptree yucca leaves are slender and comparatively flexible. Woodrats relish them. They shear the leaves off at the base, leaving the yucca looking like it has received a buzz cut, then tote the leaves off for food and nest-building material. Cattle, deer, pronghorn, and other grazers nibble on soaptree yucca leaves and search out the succulent young flower stalks. Birds like orioles and cactus wrens hide their nests deep in the protected heart of the dense leaf rosettes. Where trees or utility poles are lacking, tall yucca stalks provide perches for shrikes and hawks.

If you travel across Southern New Mexicos grasslands in late spring or early summer, you can’t miss soaptree yucca and its towering ivory “candles.” But to really appreciate our state flower, visit the yucca forests on a moonlit night, when the blossoms glow and softly scent the air.

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Technorati Tags: plant,plants,tumbleweed

The spring winds blew the other afternoon, hurling great clouds of soil from newly-plowed fields into the air. Tumbleweeds bounced across roads and open spaces like giant soccer balls. When my step-daughter, Molly, and I rode our bikes across town the next morning, drifts of prickly tumbleweed skeletons turned the sidewalks into a slalom course.

A symbol of the West in movies and popular songs, tumbleweed is actually not native here at all. As Russian-thistle, its other common name, suggests, tumbleweed comes from Russia’s arid shrub steppes, half a world away. After hitching a ride to America in the 1870s with flax seed brought by Ukrainian farmers, tumbleweed spread like wildfire across disturbed places in the West, colonizing plowed prairies, overgrazed rangelands, road edges, corrals, and the bare earth of abandoned farms. No wonder that one Hopi name for tumbleweed is “white man’s plant.” By the time the Sons of the Pioneers recorded “Tumbling Tumbleweeds” in 1934, this invader had come to symbolize the rootless, restless Western culture.

Tumbleweed is now ubiquitous throughout the West. When young, bright green, and succulent, tumbleweed, a relative of spinach, attracts browsers and grazers. Desert cottontails and small rodents nibble on its high-calorie shoots, as do pronghorn antelope, bighorn sheep, domestic sheep, and cattle. But this fast-growing annual quickly becomes inedible, forming a globular mass of tough and prickly stems, as it grows up to six feet high, and fifteen feet across.

One way that botanists classify plants is to label them by the conditions they prefer: for instance, plants adapted to saline soils are “salt-lovers”; others requiring the damp soils along streams are “water-lovers.” Tumbleweed is a “wind-lover.” Tumbleweed’s minute flowers, containing no nectar to attract bees, wasps, hummingbirds, or other nectar-sipping pollinators, depend on the wind, releasing clouds of tiny pollen grains to float on the river of air. Because of its windborne pollen and its abundance, tumbleweed is a major irritant to hay fever sufferers in the Southwest.

Wind assists tumbleweed again when the seeds are ready to disseminate. Tumbleweed’s large, dry, ball-shaped skeleton sways with the tug of the wind, until eventually the single stem snaps, freeing the plant to bound across the arid soil. With each bounce, tumbleweed drops some of its prodigious number of seeds – a single plant can produce up to 200,000 seeds – spreading its genes far and wide before piling up in the lee of a building or snagging on a fence.

Like them or not, tumbleweeds are a part of the modern West, a reminder of our heedless tinkering with the balance of arid environments. As spring winds propel tumbleweeds into the air to leap across the landscape and scatter their progeny, I dream of the day when their seeds will have a hard time sprouting in healthy deserts and grasslands.

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Technorati Tags: Mistletoe,plants

While walking the road along the dry irrigation ditch behind my house one cold afternoon, I looked over at a row of tall, winter-bare Lombardy poplars. Their leafless branches stood out like bleached skeletons against the blue sky – except for a large, ball-shaped olive-green mass growing from one branch: a mistletoe.

Mistletoe, the plant made into Christmas “kissing balls,” is one of the few truly parasitic flowering plants. Instead of producing its own food, mistletoe feeds on trees. When a sticky mistletoe seed sprouts on a tree branch, it sends a root into the tree’s veins, and draws its food and water from the tree. Mistletoe grows into a dense mass of many-branched stems, well-described by its Navajo name, “basket on high.” Eventually, however, a mistletoe may be doomed by its own success: dense mistletoe growth may kill its tree host.

Many different species of mistletoe grow in the Southwest, parasitizing deciduous and coniferous trees from the hot deserts to cool mountain forests. Different mistletoe species parasitize different tree species, and have evolved characteristics to fit each niche. Mistletoes that feed on desert trees, such as mesquite, ironwood, and paloverde have minuscule, scale-like leaves in order to conserve water. However, mistletoes growing in wetter places grow large leaves, like the mistletoe I spotted in the Lombardy poplars, which also grows in cottonwoods and ash trees. This mistletoe is widely used for Christmas decorations because of its large, pretty, oval, green leaves and glistening white berries. Green mistletoes like this one manufacture chlorophyll, and produce some of their own food. Yellowish or brownish mistletoes are completely parasitic, lacking chlorophyll altogether.

One of the completely parasitic mistletoes, juniper mistletoe, or bellota de sabina in northern New Mexico, is used in traditional medicine. Some curanderos prescribe it to staunch bleeding and induce abortions in sheep and goats. Navajos make a soothing lotion for insect bites and to cure warts by boiling equal amounts of the mistletoe and the juniper that it grows on.

The bright coral-pink berries of the mistletoe of mesquites and other desert trees constitute the major winter food of many birds; phainopeplas and robins, in particular, consume great quantities. (In fact, phainopeplas – black, robin-sized desert residents sporting striking crests – are so dependent on mistletoe berries that if the winter crop is scant, they do not breed the following spring.) Mistletoe, in turn, depends on avian consumers to spread its seeds. The sticky seeds pass through the bird’s gut undigested, and are deposited in a pat of fertilizer – bird scat – on a branch, where they sprout.

The mistletoe I spotted in the Lombardy poplars nearby is the kind used for Christmas decorations. Perhaps I’ll cut a few of its branches to make a kissing ball for my house. I don’t know why mistletoe is associated with kissing, but I don’t mind taking advantage of the tradition!

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Technorati Tags: Cottonwood,cottonwood tree,plants,trees

Autumn slips across the desert quietly. Although nights grow chill, summer’s heat lingers in the afternoons, and the greenery brought on by summer rains simply fades to dusty olive, bleached straw, and weathered brown. As the soil dries out, mesquites, desert willows, and ocotillo drop their leaves without any fanfare. But here and there where water flows – a spring, stream, an irrigation ditch, or a river – autumn shows in the rich yellows and golds of cottonwood trees.

It is hard to find a cottonwood in the desert nowadays. Where tall cottonwood overstories once marked the high-water lines of desert rivers and traced the sputtering lines of streams and springs, only an occasional twisted survivor remains. The disappearance of the cottonwoods and the associated bosques, Spanish for “woodlands,” and cienegas, “marshes,” resulted from several causes. Woodland clearcutting and livestock overgrazing in the late 1800s denuded whole watersheds, stripping the plant cover so that rainwater roared off, carrying the precious soil and causing once-permanent streams to alternate between brown floods and dusty drought. Steep-walled arroyos now gouge the landscape where streams and rivers once meandered, lined by cottonwoods and bosques. Dams controlled river flooding, but without the scouring action and rich sediment deposited by high water, cottonwoods could not reproduce. Farmers cleared the bosques and cottonwood overstory to create fields in the fertile soils of the river floodplains.

But where cottonwoods remain, the gradually shortening days of autumn bring color to their broad, triangular leaves. As the number of hours of daylight decrease, the trees stop producing chlorophyll, the green pigment that both colors their leaves and helps them produce food from the sun’s energy. The chlorophyll slowly breaks down and disappears from the leaves, revealing underlying pigments which color the waxy leaves golden yellow.

Many Southwest place names – such as Alamogordo, New Mexico, for instance, named “fat cottonwood” for a long-vanished giant – commemorate the cottonwood of the Southwest’s deserts and grasslands. This species grows as tall as 80 to 90 feet, supporting a broad, open crown with large, spreading branches. Grey, deeply furrowed bark clothes a fat trunk that can swell to more than five feet in diameter. The largest-known example of this cottonwood grows on a ranch in western New Mexico and boasts an enormous trunk nearly 12 feet across – 38 feet around – and a crown spread of 102 feet!

The yellow and gold tinging cottonwood leaves in the fall signals the tree’s preparations for the oncoming winter. Despite the waxy coating that gives the leaves their slight shine, cottonwoods (and all deciduous trees and shrubs) shed their leaves so that the leaves will not respire more water than the tree’s roots can suck from the dry soil over the winter, dehydrating the tree. And by preparing for winter, the cottonwood brings a blaze of autumn color to the desert.

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Technorati Tags: Agaves,plantlife

One spring afternoon, I noticed an odd plant in a nearby yard. The plant, a huge clump of leathery, blue-green leaves nearly as tall as I am, sprouted a stout green flower stalk from its center. Each foot-wide, six-foot-long leaf grew upwards and then drooped over, pointing a stilletto-spined end outwards. The flower stalk looked like a giant asparagus stalk and gave away the odd plant’s identity — a common century plant or agave.

Agaves, characteristic of New Mexico’s Chihuahuan Desert and grasslands, live surprising lives. Agaves spend their first 5 to 35 years quietly growing a clump of long, stiff and leathery leaves in which they store food and water. But once mature, these succulent relatives of lilies squander all on one glorious-but terminal-burst of reproduction. A flower stalk spurts from the center of the leaf rosette, growing as fast as a foot a day and up to 15 feet tall. As the stalk grows, it draws its energy and water from the now-withering leaves. Soon dozens of buds swell along the stalk, and eventually open at night into big, tubular flowers that emit strong, musky fragrances, attracting bats, insects and other pollinators. By the time the flowers have matured into seeds, the agave plant itself is gray, shriveled, dead.

Large agaves and some nectar-feeding bats have a special relationship. The bats migrate north just as the agaves bloom; the big plants depend on the bats for cross-pollination. Agave flowers are specially designed for these bats: They smell like rotten meat, a scent attractive to the bats; grow on tall stalks, making access easy for the hovering drinkers; their nectar secretions peak between 8 and 10 o’clock at night when the bats are most active; and the nectar is high in the exact nutrients that bats need for fuel.

Agaves once supplied food, fiber for rope and cloth, soap, and other necessities for desert-dwelling people. Southern New Mexico’s Mescalero Apaches are named for their trade in and diet of mescal, Spanish for “agave.” Mescal pits-rock-lined pits built for roasting the young flower stalks and the succulent heart of the leaf rosette-are common Southwest archaeological sites. People in northern Mexico still harvest and roast agave to produce pulque, which can be distilled into mescal and tequila. So much bootleg mescal is now being produced that wild agave populations are in danger from overharvesting.

For the next several weeks, I watched the agave flower stalk spurt upwards. Then came tragedy: Just before it burst into bloom, I found the stalk lying on the ground, felled by a chain saw. The withered plant was uprooted, dead. How sad to cut the big plant’s life short just before its final burst, and deprive the bats, hummingbirds, moths and other pollinators of their banquet!

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