biloba – two-lobed in reference to the leaves, which are sometimes incised or divided

Native range: S. China

Leaves:

• alternate (~ clusters of 3–5 on spurs, or dwarf shoots)
• fan shaped w/ parallel veins
• incised (bifid lobes)
• dichotomous venation, or unconnected veins (veins at the margins that are not connected basally) and veins that end a considerable distance from the margin

Cones:

• dieoceious
• male – catkin-like
• female:
  • small
  • stalked seed with fleshy aril
  • looks like silver plum
• smelly pulp
• edible

Other characteristics:

• open branching pattern
• leaves turn golden yellow in fall
• often drop a major proportion of their fall foliage over a short period of time, sometimes a single night, creating a yellow carpet beneath a tree

Relevant info:

• ancient tree used medicinally
• ‘Living fossil’, sole survivor of an ancient group of trees that date back >200 million years ago (before dinosaurs)
• only living bridge between ‘higher’ and ‘lower’ plants (i.e., ferns and conifers)
• according to fossil record, ancient members of this genus typically occurred in riparian plant communities with Cercidiphyllum and Metasequoia
• widely cultivated as an ornamental, probably for more than 3,000 years
• certain varieties used as street trees
• resistance to herbivory makes species popular in cities
• nurseries typically sell only male trees (fruitless) because female trees produce seeds encased in fleshy, fruit-like coverings which, at maturity in autumn, are messy and emit a noxious, foul odor upon falling and splitting open
• ginkgoic acid in the fleshy seed coat causes allergic contact dermatitis in humans
• sacred to Buddhists and often planted near temples
• endangered according to IUCN (on its Red List)

Ecology & Adaptations:

• native to south-central and southeastern China, long cultivated
• introduced to north-central China, South Korea and Japan
• scattered in broadleaved forests, in moist, deep, sandy soils in full sunlight; in valleys on acidic, well-drained, yellow loess (pH = 5–5.5)
• 300–1,100 (1,300) m.
• complex phenology (timing) of sexual reproduction cycle may constrain the species’ ability to migrate, independently of humans, into cold-temperate regions with short growing seasons, and probably accounts for its limited, warm-temperate distribution as a wild or semi- wild tree in the mountains of central China
• pollination by wind
• sexual reproduction:
  • many aspects are influenced by temperature, which varies with latitude and elevation across species distribution; trees typically reach sexual maturity at 20 yrs
  • reproductive organs produced on short shoots in the axils of bud scales and leaves
  • catkins emerge before the leaves and fall off immediately after shedding their pollen
  • when the ovule is receptive, secretes a small droplet of mucilaginous fluid from a tiny opening, which captures airborne pollen
  • retraction of this droplet at the end of the day brings the pollen into the pollen chamber
  • once inside ovule, male gametophyte develops over 4 to 5 months, ultimattely with the production of a pair of multiflagellated spermatozoids, one of which fertilizes a waiting egg cell
• seed dispersal:
  • consumption of fruits by wild cats (e.g., leopard cat, masked palm civet) in China aid in seed dispersal and germination (via exposure to acids of animal gut)
  • once seeds fall to the ground in the autumn and decay, fleshy seed coat exudes butanoic and hexanoic acids, which produce an unpleasant rancid-butter-like smell, probably mimicking the smell of carrion (dead animal flesh) to which the wild cats and other carnivores would be attracted
• seed germination:
  • removal of fleshy seed coat appears to be necessary for seed germination
  • exposure to cold temperatures of winter appear to increase germination rates
• vegetative reproduction – sends up new shoots from roots, which contributes to longevity of the clone
• herbivore/pathogen defense:
  • ginkgotoxin in the seeds is a neurotoxin that induces seizures in animals
  • leaves are resistant to many pathogens and herbivores because of the presence of toxic leaf compounds, such as terpenoids (ginkgolides, bilobalides), flavonoids, and ginkgotoxin
  • plant tissues that are attacked by herbivores also emit volatile organic compounds (VOCs), that may induce defense on the same or different plants
  • bark contains tannins