The Island’s flora lives in specific zones. Understanding these zones helps with identification and appreciation of the flora. From the Mangrove Swamps that cover the wet coastal zone, the Prickly Pear Cactus of the Arid Lowlands, the Scalesia Trees, to the Miconia of the higher Humid Zones. The Galapagos hosts an interesting array of flora.
Climate on the islands varies from dry low areas along the coast, to the high moist areas near the volcano tops. There are 7 zones within the archipelago, and these are the: Coastal Zone, Arid Lowlands Zone, Transitional Zone Scalesia Zone, Brown Zone, Miconia Zone, and Pampa Zone.
The Arid Zones is the most extensive vegetative zone. It is a semi-desert forest dominated by deciduous trees and shrubs. The plants have adaptations to withstand drought. There are great numbers of endemic species, like Lichens which are abundant in this zone because they are tolerant of dry conditions and are capable of absorbing moisture from the occasional garua mist.
As an island slopes from the beach to an elevation of about 197 ft (60 m), an arid desert-like zone occurs. This region is home to the many Cacti that live in the Galapagos including the Prickly Pear Cactus, Lava Cactus, and Candelabra Cactus. Vine plants also make their home in the Arid Lowlands. The endemic lava morning glory and endemic passionflower can be found in this zone.
At the top of the Arid Lowlands the silvery leafed Palo Santo Tree with its collection of lichens can be seen.
It is intermediate in character between the scalesia and arid zones, but dominated by different species than either of the adjacent zones. The forest is still mainly deciduous, it is much more dense and diverse than forest of the arid zones, and it is often difficult to say whether any species is dominant.
Higher up in the island, plants becomes more abundant. In the Transition Zone, plants from both the Arid Lowlands and the Upper Moist Zones grow. This zone is home to a variety of small trees and shrubs, including the endemic Pega Pega Tree and the endemic Guayabillo, which produces a small white flower that develops into a fruit similar to the Guava fruit.
The Galapagos Tomato, endemic to the islands is a salt resistant tomato that has been used to create a hybrid, which is capable of growing in salty soil around the world.
The transition zone merges into the evergreen Scalisia forest, which is a lush cloud forest, dominated by Scalesia Pedunculata trees. This type of forest occurs only on the higher islands and, being the richest zone in terms of soil fertility and productivity, it has been extensively cut down for agricultural and cattle ranching purposes. The Scalesia forest is diverse, and has many endemic species.
Humid Epiphytes like orchids, mosses, ferns and lichens thrive in this zone's constant moisture, as well as ornate trees and shrubs with color and charm. Scalesias and Pisonias are abundant at this degree of humidity. Not much is said about the highlands of Galapagos, but in reality this is an amazing cloud forest with unique features.
The Scalesia Zone is the lowest of the "humid" zones. This zone is named for the daisy tree that grows between 970 and 1970 ft (300 - 600 m) in elevation. The Scalesia is one of the few trees in the Aster Family, and grows to16 - 50 ft (5-15 m) in height. Its trunk and branches are covered with moss and lichens. This area is humid, and gives the feeling of being in the rainforest.
Scalesia Trees have been greatly reduced in numbers since humans arrived to the islands. Along with them came pigs and goats, which devoured the young plants and fed off of older plants. People also introduced the Guava plant, which is dense, and its growth patterns steal nutrients; it gradually makes it impossible for competing plants to survive.
The Brown Zone is intermediate between the dense Scalesia forest and the Miconia shrub vegetation. It is an open forest dominated by Cat’s Claw, Tournefortia Pubescens, and Aunistus Ellipticus. Trees are heavily draped with epiphytes, mosses, liverworts and ferns, which give this zone a brown appearance during the dry season. This zone has disappeared due to human occupancy.
The southern slopes of San Cristobal and Santa Cruz are the only places where there is a dense shrubby belt of Miconia Robinsoniana. Native trees are absent from this zone, and ferns are abundant. There are also more liverworts than anywhere else.
Above the Scalesia Zone at 1,950 – 2,300 ft (600-700 m) is the humid zone named for the Miconia shrub that once dominated this region. The Miconia Robinsoniana grows at heights of 10-13 ft (3-4 m). It's leaves are easily identified because of their yellow or reddish shading around the edges.
The Miconia is endemic to the Galapagos, but since the arrival of man, it has become the most endangered plant in the islands. Introduced cattle have grazed the Miconia into dangerously low levels.
There are virtually no trees or shrubs, and the vegetation consists largely of ferns, grasses, and sedges. This is the wettest zone, specially during the garua season, receiving as much as 2.5 m of rain in some years.
In the populated islands, this is considered farmland or Pampas. The temperature is low, and grass is abundant; good to cultivate commercial products and raise cattle.
On islands of 3000 ft (900 m) in elevation and higher, the highest level of vegetation in the Galapagos can occur; the Fern-Sedge Zone or Pampa Zone. The appearance of this zone depends on the amount of moisture it receives. The tall Galapagos Tree Fern and Liverworts are commonly found in this zone.