In rainier areas, the thorn forest grades into tropical deciduous forest. This is the “friendly” or “short-tree” forest, blanketed by a tangle of summer-green leaves that fall in the dry winter to reveal thickets of branches. Some trees show bright fall reds and yellows, later blossoming with brilliant flowers—spider lily, cardinal sage, pink trumpet, poppylike yellowsilk (pomposhuti), and mouse-killer (mata ratón), which swirl in the spring wind like cherry-blossom blizzards.

The tropical deciduous forest is a lush jungle coat swathing much of the coastal Puerto Vallarta region. It is especially lush in the mountains above San Blas and along the low summit of Highway 200 over the Sierra Vallejo north of Puerto Vallarta. Where the mountains rush directly down to the sea, the forest appears to spill right over the headland into the ocean. Vine-strewn thickets overhang the highway like the edges of a lost prehistoric world, where at any moment you expect a dinosaur to rear up.

The biological realities here are nearly as exotic. A four-foot-long green iguana, looking every bit as primitive as a dinosaur, slithers across the pavement. Beside the road, a spreading, solitary strangler fig (Ficus padifolia) stands, draped with hairy, hanging air roots (which, in time, plant themselves in the ground and support the branches). Its Mexican name, matapalo (killer tree), is gruesomely accurate, for strangler figs often entwine themselves in death embraces with less aggressive tree-victims.

Much more benign is my favorite in the tropical deciduous forest: the Colima palm (Orbignya guayacule), or guaycoyul or cohune, which means magnificent. Capped by a proud cock-plume, it presides over the forest singly or in great, graceful swaying groves atop seacliffs. Its nuts, harvested like small coconuts, yield oil and animal fodder.

Excursions by jeep or foot along shaded off-highway tracks through the tropical deciduous forest can bestow delightful jungle scenes; however, unwary travelers must watch out for the poison oak–like mala mujer (evil woman) tree. The oil on its large five-fingered leaves can cause an itchy rash.