4. Panicum hillmanii Chase [syn.: P. capillare subsp. hillmanii (Chase) Freckmann et Lelong] (N-Am.) – A very rare but possibly overlooked, usually ephemeral alien. Formerly exceptionally found in the Vesdre valley, probably as a wool alien (1882). Increasingly seen since the 1980’s, predominantly by roadsides (especially highways) and probably always associated with grain importation. In the port of Antwerp Panicum hillmanii locally persists in abundance since ca. 10 years by railway tracks; it may well be naturalized and spreading in that area. By 2013 at least three stable populations are known: railway yard W of Albertdok and by railway tracks N of Derde Havendok and E of Leopolddok. Elsewhere in Europe (Austria, France, Germany,…) recorded as an agricultural weed in maize fields and likely to occur as such in Belgium as well.
For the identification of Panicum hillmanii mature caryopses are preferably examined (although palea length is also a useful feature). Delimitation from Panicum capillare is straightforward in Europe and both are therefore treated at specific rank in this treatment (contrary to Freckmann & Lelong 2003).
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