The green-leaved variant of Eucalyptus largiflorens: a story involving hybridization and observant local people

Eucalyptus largiflorens (Black Box) is the most common tree in the Chowilla anabranch system on the Murray River floodplain. It typically has dull, glaucous, grey-green leaves. Occasional trees with smaller, glossy green leaves (Green Box) occur scattered amongst the Black Box. In areas with increasing salinity, they usually appear much healthier than adjacent, normal Black Box trees. Green Box plants are intermediate between normal Eucalyptus largiflorens plants and Eucalyptus gracilis plants in many morphological and allozyme characters, strongly suggesting that they are hybrids between those species. Green Box plants tolerate salinity better and use water more conservatively than normal Black Box plants, traits that they have probably inherited from Eucalyptus gracilis. In 1994, the Botanic Gardens of Adelaide used tissue culture and micropropagation to produce nearly 9,000 cloned Green Box plants which were planted out on Riverland floodplains. Since the 1990s, the high cost of producing clonal plants has meant that no further such plantings have occurred. Because Green Box plants can be a considerable distance from the nearest plants of one putative parent (Eucalyptus gracilis), more detailed studies could contribute to the existing work on such phantom hybrids