■ イチョウ【銀杏】 the ginkgo tree
■ ぎんなん【銀杏】 the edible ginkgo 'nut'
■ ぎんきょう【銀杏】 (nonstandard reading)
These two words are (confusingly) written with the same kanji, and refer to Ginkgo biloba, or the maidenhair tree. This is a "living fossil", the sole surviving member of the ancient botanical division ginkgophyta (one of three divisions of the gymnosperms, of which the best known is the conifers). It was first known to the West after discovery in Nagasaki by Engelbert Kaempfer in 1690.
It is only possible to determine the reading of the characters 銀杏 by context. In a restaurant, they will normally refer to the edible seed kernels (strictly not fruit), and so are read ぎんなん. (The kernels are an essential ingredient of 茶碗蒸（ちゃわんむし）. )The tree itself is more likely to be referred to as イチョウ written in katakana. The reading ぎんきょう does not appear to be standard, though it is found in some large dictionaries: it holds an obvious clue to the Latin and English name "ginkgo".
For photographs and more description, see the author's "Plant-Watcher's Page": Ginkgo and the follow-up, Ginkgo Origins including a discussion of the source of the mysterious "ginkgo" name.
This entry was created by Brian Chandler.