White Poplar (leukê)
LEUKE (Leuce) was an Okeanid-nymph abductedto Elysion (Elysium) by the god Haides where she was transformed into a white poplar tree.
Her story was probably connected with the white poplars which grew on the banks of the river Akheron (Acheron) in Thesprotia--a region famed for its necromantic oracle of Haides.
Leuke was probably the same as Leukippe, an Okeanid-nymph companion of the goddess Persephone mentioned in the Homeric Hymns.
OKEANOS (Servius on Virgil's Eclogues 7.61)
LEUCE (Leukê), a nymph, a daughter of Oceanus, who was carried of by Pluto; and after her death, was changed into a white poplar in Elysium. (Serv. ad Virg. Eclog. vii. 61.)
Source: Dictionary of Greek and Roman Biography and Mythology.
CLASSICAL LITERATURE QUOTES
R. E. Bell, Women of Classical Mythology (sourced from Servius on Virgil's Eclogues 4.250) :
"Leuce was a nymph, a daughter of Oceanus, who was carried off by Hades. After her death she was changed into a white poplar in Elysium. The white poplar was sacred to Hades. When Heracles returned form the underworld, he was crowned with poplar leaves."
Pausanias, Description of Greece 5. 14. 2 (trans. Jones) (Greek travelogue C2nd A.D.) :
"Herakles found the white poplar (leukê) growing on the banks of the Akheron (Acheron), the river in Thesprotia, and for this reason Homer calls it Akherois (Acherois). So from the first down to the present all rivers have not been equally suited for the growth of plants and trees. Tamarisks grow best and in the greatest numbers by the Maiandros (Meander) . . . So it is no wonder that the white poplar grew first by the Akheron."
- Pausanias, Description of Greece - Greek Travelogue C2nd A.D.
- Women of Classical Mythology - English Encyclopedia of Mythology C20th A.D.
Other references not currently quoted here: Servius on Virgil's Eclogues 7.61.