Because of the wide range of temperature, the native flora of Mexico is extremely varied. Cactus, yucca, agave, and mesquite are plentiful in the arid north. The tierra caliente is thickly grown with an immense variety of plants, which form a dense tropical jungle in some areas. The trees in this zone include valuable hardwoods, as well as coconut palms, gum trees, and almond, fig, and olive trees. On the mountain slopes grow oaks, pines, and firs. Arctic vegetation is found at the highest elevations in Mexico.