Few plants can grow in the bone-dry conditions of Peru’s southern and central coast, which is dominated by shifting sand dunes and arid desert. The irrigated valleys, however, are covered in cash crops, including olives, grapes, nuts, and a range of fruits and vegetables. In Peru’s northern valleys, the hotter temperatures are ideal for the cultivation of cotton, rice, mangos, lime, and sugarcane.
As the Humboldt Current eases off Peru’s coast at the tip of the Península de Illescas, west of Piura, trade winds bring humidity and even some rain to the coast. The coast northeast of Chiclayo is covered by vast tracts of bosque seco, a scraggly low-lying forest composed mainly of algarrobo (carob), a mesquite-like tree whose sweet pods are the base of the algarrobina cocktail. Other trees in these forest include ficus, zapote, and vichayo.
Even farther north, the climate turns subtropical and occasional patches of palm trees line up near the beaches, along with the large mangrove swamps near Tumbes. The swamps are protected as part of the Santuario Nacional Manglares de Tumbes, which includes Peru’s only chunk of Pacific tropical forest. There are orchids and gigantic trees such as the ceibo, with its umbrella-shaped crown, and the pretino, which drops seed pods the size of basketballs.
The high grasslands region, or puna, is home to a collection of bizarre plants with endless adaptations for coping with the harsh climate. Many of them have thick, waxy leaves for surviving high levels of ultraviolet radiation and fine insulating hairs in order to cope with frequent frosts. They grow close to the ground for protection from wind and temperature variations. In Peru’s north, wet grasslands known as páramo stretch along the northwestern edge of the Andes into Ecuador. The páramo has a soggy, springy feeling underfoot and serves as a sponge to absorb, and slowly release, the tremendous amounts of rain that fall in the area.
Peru’s most famous highland plant, the Puya raimondii—baptized after Antonio Raimondi, the Italian naturalist who studied it—grows in the puna, from Huaraz all the way south to Bolivia. The rosette of spiky, waxy leaves grows to three meters in diameter and looks like a giant agave, even though the plant is in the bromeliad family along with the pineapple. The Puya lives for a century and, before it dies, sends a giant spike three stories into the air that eventually erupts into 20,000 blooms. Once pollinated, the plant’s towering spike allows it to broadcast its seeds widely in the wind.
The spiky tussocks of grass known as íchu are the most ubiquitous feature of Peru’s high plains. Highlanders use this hardy grass to thatch their roofs, start their fires, and feed their llamas and alpacas. Cattle, which were imported from Europe in the 16th century by the Spanish, are unable to digest it. Cows can only eat the íchu when it sprouts anew as a tender green shoot. Hence, highlanders burn large tracts of hillside every year to make íchu palatable for cows.
The high deserts of southern Peru, such as those on the way to the Colca Canyon, are so dry that not even íchu can survive. Instead, green blob-like plants called yareta spread along the rocky, lunar surface. This plant’s waxy surface and tightly bunched leaves allow it to trap condensation and survive freezing temperatures. It is currently considered an endangered species.
A few trees can be found in Peru’s montane valleys. Eucalyptus, which was imported to Peru from New Zealand, is used widely by highlanders for firewood and ceiling beams. Eucalyptus is useful but also highly invasive; its rapid spread has greatly reduced the numbers of Peru’s most famous highland tree, queñual, currently also endangered. This scraggly, high-altitude , onion skin–like tree can still be seen in abundance, however, in the Parque Nacional Huascarán, especially on a three-kilometer trail known as María Josefa that starts at the shores of Lagunas Llanganuco.
The cloud forests that blanket the eastern escarpments of the Andes are a remarkable tumble of gnarled trees that cling to the steep, rocky soil. These trees have evolved to trap the thick blankets of mist that form when humid jungle air cools as it rises over the Andes. Aerial plants, such as ferns, mosses, orchids, cacti, and bromeliads, cover the trees and are collectively known as epiphytes. Because they have no roots to the soil, they must gather all of their water and nutrients from the passing mist. This forest has a dark, primeval feel and is seen in the surrounding areas of Moyobamba and Tarapoto, Machu Picchu, throughout the Chachapoya region, and on the road to Parque Nacional Manu. The Peruvians somewhat poetically call cloud forest the ceja de selva or the “eyebrow of the jungle.”
The forest takes on a whole different feel farther downhill in the lowland tropical rainforest, where steep slopes give way to swampy soil and the rivers become slow and muddy. The trees are huge, often over 60 meters tall, and the understory is dark and curiously free of plants. Huge gray vines, as thick as the human body, descend from the highest branches into the ground. These are the strangler figs called matapalo, which begin life high in the canopy where birds and bats drop their seeds after gorging on the fig fruit. After dropping their vines to the forest floor, these vines merge together and form a sheath that envelops the tree, slowly choking off its nutrients. When the host tree dies, the parasite strangler fig remains in its place. They are often the largest, noblest trees in the forest, and it is hard to believe they began life as assassins.
Life in the rainforest is a battle for sunlight. This becomes readily apparent to those who climb up to the tree platforms or canopy walkways that have been built in the jungle lodges. Perched high in the canopy are an astounding number of epiphytes, far greater than in the cloud forest. Each of these plants has made adaptations to deal with the intense sunlight and evaporative breezes of the upper canopy. Tank bromeliads have long leaves that work as troughs to collect rain, while the orchids store water in their bulbous stems. All the plants, especially the cacti, have tough, waxy skins to retain moisture. These epiphytes are here not only for the sunlight, but also for the breezes that help disperse seeds and the vast number of bats, birds, and insects that forage in the canopy and serve as pollinators.
The fight for sunlight is evident on the forest floor when a large tree falls over, dragging its vines and smaller trees along with it. The sun-filled clearings created by falling trees are called “light gaps” and form fascinating mini-ecosystems for fast-growing pioneer trees, such as the cecropia. Its thin gray trunk, often marked with white rings, twists in odd shapes to catch the sunlight with its huge palm-shaped leaves. These clearings are wonderful places to examine the epiphytes, insect nests, and other forms of canopy life.
Large rainforest trees include mahogany (caoba), cedar (cedro), and tornillo, a highly valuable wood for making furniture that can now be found only in Peru’s stands of primary forest. You might also see the Brazil nut tree, which drops round pods containing seeds used to make organic oils and lip balms. There is also the kapok, also known as ceiba, which is readily identifiable by its huge red seed pods hanging from branches. When these pods open, they release seeds that are borne by the wind on cottonlike tufts, which Amazon natives use for making hunting darts. At the ground level, the kapok stands out for its huge buttress roots, which fan out in all directions and are often wider than the tree itself.
If you scuff the ground with your foot you will understand the reason for the roots. Jungle soil is amazingly poor because all the minerals are either sucked up by the voracious competition of plant life or leached away by the constant rains. As a result, even the roots of the largest trees run along the surface in a desperate search for minerals. Because rainforest trees lack the deep taproots of temperate-forest trees, they need buttress roots to help stay upright, especially during the violent windstorms that snap the tops of many trees right off.
Another surprising difference between temperate forests and rainforests is the age of the trees. In the United States, old-growth forests take centuries to develop. But rainforests are much more dynamic—the average life of a tree here is a mere 80 to 135 years.
For people used to the pines and oaks of temperate forests, the sheer variety of trees in the rainforest can be overwhelming. There are more than a thousand different tree species in Peru’s Amazon, and even finding the same tree twice can be a challenge. There is no complete guide to rainforest trees; even if one existed, it would be the size of a telephone book.
Instead of trying to keep a mental catalog of the trees you see, it makes more sense to try to understand how different trees use common defenses to survive. The thorns and spikes on many rainforest trees serve as a protection against animals, while peeling bark prevents vines from climbing the trunk. Many leaves have thin hairs or contain a complex array of toxins that serve as protection from the predation of caterpillars and insects.
Other trees have developed symbiotic relationships to survive. The palo santo (holy tree), for instance, has hollow chambers and a gooey nectar that provide food and lodging to fire ants. These ants are totally dependent on the tree for survival and will chase off any predator that would otherwise feast on the tree.
© Ross Wehner and Renée del Gaudio from Moon Peru, 3rd Edition