Megaflora
Megaflora (from Greek μέγας megas "large" and Neo-Latin flora "plant life") refers to an exceptionally large plant species. Examples  of megaflora include the Sequoioideae of California and a number of extinct plant species from the Mesozoic. Culture
Most Proto-Indo-European mythologies feature Megaflora in the form of a World Tree, a Tree-of-Life, axis mundi, or Sacred Tree. Some examples are the Ashvattha in Hindu mythology, Yggdrasil in Norse mythology, and égig érő fa in Hungarian mythology. Notable texts like the Epic of Gilgamesh and the Book of Genesis contain similar motifs, drawing inspiration from ancient iconography. Often symbolizing rootedness, spirituality and fruitfulness, these plants have become central to the high fantasy and science fiction genres. The Two Trees of Valinor from The Lord of The Rings and the Hometrees of Avatar are two mainstream examples. Examples

Africa
Adansonia digitata

Oceania
Eucalyptus regnans

Eurasia
Ficus benghalensis

Central and South America
Ceroxylon quindiuense

Puya raimondii
Victoria amazonica

North America
Sequoia sempervirens
Sequoiadendron giganteum
Picea sitchensis
Pseudotsuga menziesii var. menziesii

Asia
Shorea faguetiana
Koompassia excelsa

Rafflesia arnoldii
Amorphophallus titanum

See also
Megafauna
Megaherb

References

Flora