The Naturalized Flora of Hong Kong: A Comparison with Singapore

At least 144 exotic species of vascular plants have become naturalized in Hong Kong. The families As- teraceae, Poaceae and Fabaceae account for 45%. Of the total, 52% are probably introduced from tropical America, 18% from northern Eurasia (including Europe), 15% from Africa and Madagascar and 10% from tropical and subtrop- ical Asia. Recognizably exotic species are largely confined to open, recently-disturbed sites and have not significantly invaded the secondary grasslands and shrublands which cover most non-urban areas in Hong Kong. Only 48% of the Hong Kong species are also naturalized in Singapore. This is best explained by climatic differences. Hong Kong's cool winters apparently permit the establishment of exotics of temperate origin while excluding some tropical species.