Plants must adapt to the soil, sun, and rain, and Oaxaca’s astonishingly diverse plant population reflects the state’s varied landscape. Of Mexico’s 14 major vegetation zones, ranging from high desert to tropical rainforest, at least eight occur in Oaxaca.
Directly along Oaxaca’s paved national highways you can visit six of these zones: Near the seacoast lie extensive swaths of savanna, deciduous tropical forest, and pine-oak forest. Inland you can add the tropical evergreen forest, tropical rainforest, and arid tropical scrub to your botanical itinerary. Oaxaca’s remaining major two vegetation zones, the cloud forest and high coniferous forest, are accessible only on high, often roadless, mountain slopes and summits.
In their natural state, Oaxaca’s savanna lands appear as flat, palm-dotted grasslands, watery during the summer and dry and brown during the winter and spring. Although much savanna has been converted to pasture or farmland, some pristine stretches lie along the coast, notably along Highway 200 near the Lagunas de Chacahua  and along the Isthmus shoreline south of Highway 190, east of Juchitán.
Although grass rules the savanna, palms give it character. One of the most familiar in Oaxaca is the Mexican fan palm, or palma real (Sabal Mexicana), seasonally festooned with black fruit with leaves spread flat like a señorita’s fan. The palma real, sometimes called the Oaxaca palm, resembles its cousin, the palmetto of the American southeast. The palma real, moreover, doesn’t limit itself to the savanna. It appears in many other Oaxaca landscapes, notably in picturesque dwarf form in the cactus forest alongside Highway 190, just north of Huajuapan de León, in desertic northwest Oaxaca.
Visitors to Oaxaca’s coastal resorts usually enjoy the sight of plenty of coconut palms (Cocos nucifera), by many measures the world’s most useful tree. Local folks, who call it the cocotero, use nearly all of its parts: fronds for thatch, mats, and baskets; lumber for construction; and nuts for cooling drinks, fruit, candy, and oil. The coconut is completely benign with one exception: Falling coconuts are no joke. Watch out for them, especially during a breeze.
If you see what look like several grapefruits sprouting from a tree trunk, you are probably looking at a gourd tree, or calabaza (Crescentia alata), The mature gourds, brown and hard, were handsomely carved and fitted with gold handles for Aztec emperors to drink chocolate out of. Oaxacans, who still call them by the ancient name jícaras, use them as bowls (notably women, on the west Oaxaca coast, who carry them all day at market on their heads, like a hat).
Its petite, pumpkin-shaped gourds both identify and name the sandbox tree, or jabillo, because they once served as desktop boxes full of sand for drying ink. The Aztecs, however, named it the exploding tree, because its ripe fruits burst their seeds forth with a bang like a firecracker. Beware of its poisonous seeds and its irritating sap.
A mangrove wetland (manglar), a vegetation sub-zone, often borders a savanna’s watery seaward edge. Healthy mangrove wetlands are primary nurseries for uncounted forms of aquatic plants and animals. While a number of prime spots exist, Laguna Manialtepec , a half-hour drive west of Puerto Escondido , is one of Oaxaca’s richest and most accessible mangrove wetlands.
Great swaths of this “friendly” or “short-tree” forest coat Oaxaca’s coastline, especially along coastal Highway 200 around Puerto Ángel  and the Bahías de Huatulco . As the label “deciduous” implies, this is the forest where the trees, in response to the dry winter weather, go dormant and lose their leaves. For visitors, the upside to all the winter barrenness is that many trees’ leaves show bright fall colors; then, at the height of winter bleakness, they sprout profusions of bright red, yellow, pink, and white winter blossoms from apparently lifeless branches.
One of the most strikingly beautiful of these is the rosa amarilla, or yellowsilk shellseed (Cochlospermum vitifolium). Although not a rose, it looks every bit like a wild yellow rose when its big flowers sprout from bare branches in the early spring. After the flowers fall, leaves bud and apple-shaped green fruit grows, turning into brown pods, which pop open and release silky fluff.
The silk cotton tree (Ceiba pentandra), another of the tropical deciduous forest’s major actors, yields a form of lightweight, cottony kapok fiber. Local folks, who call it the cuajilote, prize it for its spectacular large white (or red in cultivated varieties) blossoms with big, brushy pink stamens. In dense forest the silk cotton tree stays relatively short, but isolated it can grow to a wide-crowned giant with bulging buttresses on the lower trunk.
Lovers of Hawaii will be pleasantly surprised to find that a number of their favorite island plants are Mexican natives. The frangipani or plumeria, prized by native Mexicans for its heavenly orange blossom–like fragrance, was first classified and named as Plumeria acutifolia by French botanist Plumier. Pick some of its white, pink, or yellow whorl-lobed five-petaled flowers and put one behind your ear to get yourself into the mañana mood.
Not nearly so benign is the mala mujer (bad woman), southern Mexico’s poison ivy bush (Cnidoscolus urens). Before venturing out through the Oaxaca coastal forest, ask someone to point out its drooping, oak-like, five-lobed leaves and tiny flowers. Otherwise, you might risk a stinging rash from the nettle-like hairs on the leaf surfaces and the long stalks.
One of the showiest of roadside inhabitants is mata ratón (mouse killer, Gliricidia sepium). Despite its fragrant spring swirls of pink and white pea-like blossoms, this plant lives up to its name. Oaxacans grind its bark and leaves with cooked corn for a very effective rat and mouse poison (which, beware, is also poisonous to dogs and cats). It can be further identified by its four- to six-inch-long seedpods.
About an hour’s drive inland, at elevations of about 5,000 feet (1,500 meters), the tropics give way to the cooling heights of the pine-oak forest, Oaxaca’s most extensive vegetation zone.
Although pine-oak forest once covered half of Oaxaca’s landscape, people, beginning thousands of years ago with Oaxaca’s original farmers, cleared much of it for fields, especially in the central valley and surrounding mountainsides. Nevertheless, extensive upland tracts of pine-oak forest still remain, doing their beneficent work, storing moisture, anchoring soil against erosion, and providing food and shelter for hosts of animals.
As you enter the pine-oak forest from lower elevations, you usually see the oaks first, occurring in two broad families. Mexicans identify them as either the encino (evergreen, small-leafed) or the roble (deciduous, large-leafed), both resembling oaks that dot the hills and valleys of California and the U.S. Southwest. Clustered in their branches and scattered in the shade are the bellota (acorns), which unmistakably mark them as oaks.
At higher elevations the oaks gradually give way to pines, which, in Oaxaca, often grow in pure stands above six or seven thousand feet (1,800–2,100 meters). Pines are easy to identify because of their long needle-like leaves, which grow in bundles, in contrast to the shorter needles of other conifers, such as spruce and fir, which commonly grow feather-shaped leaves made of rows of needles individually attached to the leaf stem.
Although pines are easily distinguished from other tree families, individual pine species are often hard to differentiate from each other. Nevertheless, examining the cones (which often conceal edible, tasty nuts) and the needles may yield identifying clues to at least a few members of this populous and very useful Mexican tree family.
Among the varieties you may encounter is the Mexican white pine (Pinus ayachuite), similar to the white pine of the western United States. Local folks, who call it the pinabete or ayacahuite, know it by its very large (more than eight inches/20 centimeters) cones and long, four- to six-inch needles, which hang in clusters of five.
Others you might see are the Montezuma pine, locally called the ocote macho (dark three- to nine-inch dark cones, long, drooping needles, five to a bundle) or the Aztec pine, or pino real (shiny, small brown one- to two-inch cones and long, bright green needles in bundles of three—very useful for turpentine, tar, soap, and medicines).
Often associated in the same territory as pines and oaks is Mexico’s renowned national tree, the ahuehuete (ah-way-WAY-tay), or sabino. Nearly every visitor to Oaxaca City  sees the country’s most famous specimen, at the village of Santa María del Tule , half an hour east of the city, where droves of visitors arrive, some on bended knee, to wonder at what is known locally as El Tule. Probably the most massive tree in Latin America, it’s as big around at the trunk as it is high: approximately 150 feet (46 meters).
In rainy foothill and low mountain areas, especially along the north Gulf slope, the lush, dense undergrowth and tall, leaf-crowned trees of the tropical evergreen forest decorate the hillsides. Here, most extensively in the north along Highway 175 around Valle Nacional, and, to a lesser extent, in the southern Sierra foothills along highways north from the Pacific coast, huge trees and vine-strewn thickets often overhang the highway. As the road curls through a dark, isolated, liana-draped canyon, momentarily you might feel as if you’re traversing a forgotten corner of some prehistoric lost world, where a last remnant dinosaur might rear up at any moment.
Overhead, huge-leafed climbing plants, such as the ceriman (Monstera deliciosa), hang by thick ropy vines on the trunks of accommodating trees. Local people, who know the ceriman as the piñanona, enjoy its sweet, juicy, corn cob–shaped fruit and find relief from aches and pains by drinking a tea brewed from its leaves.
No Oaxaca jungle trip would be complete without experiencing the strangler fig, known by the hideously accurate local label matapalo (killer tree). A strangler fig seed, once it sprouts in the crotch of a victim tree, will grow, finally entwining its host in a suffocating embrace. By then the strangler fig will have planted hairy “air roots” for ground support and will most likely go on living long after its victim has died. In a peculiarly national quirk of character, many Mexicans prize such dead victim-tree trunks. Workers scour the forests, cutting, gathering, and polishing these death embraces, to decorate living room corners or support elaborate outdoor palapa roofs, especially in fancy open-air restaurants.
In numerous stretches of Oaxaca’s tropical evergreen forest, local folks cultivate coffee beneath the shady canopy. Even if coffee (Coffea Arabica), known to its Mexican growers as cafeto, weren’t commercially important, people could still enjoy it as an attractive ornamental, with its shiny, ribbed green leaves and red holly-like berries. Even though coffee shrubs are quite common in Oaxaca’s jungly foothills, you have to look carefully for them, because they grow best in the deep shade beneath taller trees. If you don’t spot the ripe red berries, look instead for the white flowers, which are as fragrant as those of coffee’s cousin, the gardenia.
This is the “forest primeval” of legend, where heavy rains nourish grand evergreen hardwoods whose great leafy crowns tower up to 200 feet (60 meters) over layers of lesser trees. Here and there, rays of sunlight shine through and nurture a luxuriant undergrowth of palms, bamboo, orchids, and bromeliads.
The rainforest gives rise to many unique, sometimes bizarre, adaptations. The big trees fortify themselves against their top-heavy bulk by developing ponderous buttresses, reaching up to a dozen feet from the ground and spreading six or eight feet from the trunk. On the other hand, shorter, lower-canopy trees commonly drop fibrous filaments, which eventually root and grow into strange, stilt-like side-trunks as far as 50 feet (15 meters) from the original trunk.
The acknowledged king of the Mexican rainforest community is the mahogany, which local people, who call it the caoba, often point to with pride. The label refers to a number of similar trees of the genus Swietenia, which grow throughout the Mexican and Central American rainforests. Although the original mahogany (Swietenia mahogany) does not grow in Mexico, some of its cousins, such as Swietenia macrophylla, do. Oaxacans prize it for its handsome reddish wood, much valued for furniture. You can identify it by its half-foot-long slender leaves and four-inch woody fruits, curved like a vulture’s head, thus the tongue-twisting indigenous label zopilo zontecomacuahuitl (buzzard-head tree).
If, along the roadside, you spot a tall tree with diagonal slashes on its bark (for gathering sap), it’s most likely either a rubber tree or the chewing-gum tree, the chicle, locally known as the chicozapote. Chewing gum, made from the chicle’s sap (notice the Chiclets in every store), spread all over the world during the early 20th century and continues to gum up sidewalks and schoolroom desks from San Francisco to Samarkand. Additionally, chicle trees, known to botanists as Acrasuzapote, yield hard, very durable wood and, from small pinkish-white flowers, luscious round cream-colored fruits.
Of both commercial and decorative importance is the rubber tree (Castilla elastica), the source of so-called Panama rubber, once made (before synthetics) for raincoats, tennis balls, and tires. Indigenous Mexicans, who still call it the hule (OO-lay), have used it for millennia for making the ball for the ceremonial game of tlatchtli. Besides the diagonal grooves (which guide the milky sap into cups) on the trunk, you can identify the rubber tree by its foot-long elliptical leathery dark-green leaves, shiny on the top side and hairy underneath.
Among Oaxaca’s most useful rainforest natives is the chocolate tree (Theobromo cacao), the “food of the gods” of the pre-conquest kings of Mexico. Before the conquest, cacao seeds served as currency. Although these days most people don’t like to think of such things, historical records indicate that a healthy slave usually traded for about 100 beans; a small animal for perhaps about five. Most likely you’ll identify the cacao, growing as a smallish tree beneath the forest canopy, by spotting its 10-inch (25-cm) pods, which sprout right from the trunk. Workers break open the ripe leathery yellow pods to harvest the trove of beans inside.
Although it looks a lot like a desert, Oaxaca’s arid tropical scrub vegetation zone, along its northwest border with the states of Guerrero and Puebla, averages at least as much rainfall as San Francisco, California. In Oaxaca, however, the rain comes within a few summer months, often in cloudburst deluges that quickly drain away, leaving the people, animals, and plants to cope with six months of winter–spring drought.
The arid tropical scrub zone’s most successful plants, succulents, such as the cactuses and their cousins the agaves, cope by storing moisture in fleshy leaves, trunks, and stems. None is more successful or important than the prickly pear (Opuntia tuna), which, from its role in Aztec legend and consequent presence on the Mexican flag, is an important national symbol. Moreover, it is especially useful as a fence plant, for cattle food, and, most of all, for its delicious red tunas, “cactus apple” fruit, which festoon its fleshy leaves.
The prickly pear is but one member of a broad look-alike family, known in Mexico generally as the nopal. Another, especially benign, relative, known by botanists as Platyopuntia, is cultivated both for its tasty, spine-free leaves and, in Oaxaca, for red cochineal dye. Once commercially very important but now largely supplanted by synthetics, cochineal is still produced in a few Valley of Oaxaca  communities. It turns out that a certain scale insect, Dactylopius coccus, loves to munch on the Platyopuntia cactus leaves. When the insects have eaten their fill, the people gather, dry, and crush their bodies, which yield a brilliant scarlet dye prized by weavers.
Another useful domesticated member of the arid tropical scrub community is the maguey (mah-GAY), or century plant, so-called because it’s said to bloom once, then die, after 100 years of growth, although its lifetime is usually closer to 50 years. The maguey, moreover, has a number of well-known relatives. These include the very useful mescal, renowned for distilled liquor; lechuguilla, for ixtle fiber; and sisal, also useful for fiber. All of these, of the genus Agave, mature as a rose-like cluster of leathery, long pointed gray-green leaves, from which a single flower stalk eventually blooms.
Oaxaca’s two rarest plant and wildlife communities lie on the slopes and summits of high, remote mountains. Oaxaca’s most accessible cloud forests coat the northern mountains north of Ixtlán de Juárez along Highway 175 and the crest of the Mazatec’s holy mountain, Cerro Rabón, near Jalapa de Díaz. The easiest, safest route is to hire a local guide who can take you to these dewy mountaintops where, beginning around 6,000 feet (1,800 meters), you will first meet the plant and wildlife community of the cloud forest. Most botanists believe the cloud forest plants to be Ice Age remnants of a time when Mexico’s climate was much cooler than today. The proof is in the unusual specimens, many of which appear to have been transported directly across the Gulf of Mexico from the mountain forests of Georgia or North Carolina. In Oaxacan cloud forests, you may see the brilliant reds and oranges of liquid amber, the lovely white flowers of dogwood, or the white bark and tan falling leaves of beech.
Besides those, you might observe some of the cloud forest’s even more ancient vestiges, dating from the age of the dinosaurs. They include the giant Mexican tree ferns (Cyathea mexicana) with their long feathery fronds, dotted underside with ranks of brown spores. New fronds, which are born curling out of the treetops, account for the tree fern’s local name, rabo de mico (monkey’s tail).
Other such relics are the bromeliads and orchids, which as epiphytes merely enjoy physical support in their hosts’ branches (unlike parasites, which feed on their hosts). Bromeliads, members of the pineapple family, love the drippy cloud-forest environment, collecting water in their cup-like leaf folds. Of the dozens of Mexican species, one of the best known is the showy piñuela (Guzmannia lingulata), whose roseate central leaf cluster matures from green to red, finally appearing as an exotic scarlet flower.
Follow your guide even higher and you will reach the zone of high coniferous forest, which in Oaxaca exists only as a few scattered roadless, cloud-swathed green alpine islands, with vegetation resembling upper Rocky Mountain slopes in the United States and Canada. In Oaxaca, as you climb above about 9,000 feet (2,700 meters), you will likely pass through a zone of mixed pines, alders, and firs, reigned over by the regal Montezuma pine (Pinus montezumae), distinguished by its long, pendulous cones and rough, ruddy bark, reminiscent of the sugar pine of the western United States.
Ascending still higher, you may pass through pure stands of sacred fir (Abies religiosa), which your guide will probably know as oyamel or abeto. You can identify them by lovely violet-blue cones and typical fir-like needles, which grow in rows along the branches. Even higher, the firs will eventually thin out, giving way to bunchgrass and bushy Mexican juniper (monticola), with its edible, waxy blue berries.