Identification and Status of the Introduced Black Pine, <em>Pinus nigra</em>, and Mugo Pine, <em>Pinus mugo</em>, in Ontario

Recent reference texts and other sources are contradictory regarding the spread of Pinus nigra and Pinus mugo from cultivation in Ontario. Both species have reproduced from plantings along roadsides but neither has been observed to occupy habitats in Ontario to the substantial reduction or exclusion of native species, or to substantially invade natural habitats. The more widely planted Black Pine has been recorded spreading at 24 localities throughout the eastern part of southern Ontario. Mugo Pine is reported spreading at 18 locations. Although evidently much less aggressive than Scots Pine (Pinus sylvestris), both Black and Mugo pines have a potential for negative impact on biodiversity in dry, rocky or sandy habitats, especially in connection with extensive plantings. A key for the identification of two-needle pines is included. Both P. nigra and P. mugo are highly variable and reported to hybridize extensively with other species.