Chaerophyllum L.
Chaerophyllum is a genus of 33 species in the northern hemisphere (temperate regions). It is most diversified in the Mediterranean and the Caucasus regions, with two species native to North America (Spalik and Downie 2001). Recent molecular studies support the monophyly of Chaerophyllum and reveal four well-supported clades within it (Spalik and Downie l.c.). Only one species is doubtlessly native in Belgium, Chaerophyllum temulentum L. (Lambinon & Verloove 2012). Two others, Chaerophyllum aureum and C. bulbosum, are native in areas close to the Belgian frontier and could be native as well (see however Cannon 1968).
Chaerophyllum hirsutum L. is sometimes cultivated as an ornamental (Knees 1997) and has been reported as an escape from several western European countries (e.g. Clement & Foster 1994, Beringen & al. 2005). It is very indistinct and might pass unrecorded. It is best distinguished by its ciliate petals and styles that remain erect in fruit. Cannon (1968) cites Chaerophyllum hirsutum as an alien from our territory but only records from the Grand Duchy of Luxembourg are available.
1 Lower leaves 2-ternate, leaf-lobes nearly undivided === Chaerophyllum byzantinum
Lower leaves 1-3-pinnate, leaf-lobes deeply divided === 2
2 Fruit (6-) 8-12 mm long, styles at least twice as long as the stylopodium. Deep-rooted perennial (not easily uprooted) === C. aureum
Fruit 4-7 mm long, styles more or less equaling the stylopodium (at most slightly longer). Biennial, easily up-rooted === 3
3 Bracteoles nearly glabrous. Stem glabrous above, hollow === C. bulbosum
Bracteoles pubescent (ciliate). Stem hairy throughout, solid (native) === C. temulentum
Literature:
Beringen R., Dirkse G. & van Moorsel R. (2005) Gouden ribzaad (Chaerophyllum aureum L.); onopgemerkt ingeburgerd. Gorteria 31: 110-121.
Cannon J.F.M. (1968) Chaerophyllum. In: Tutin T.G. & al. (eds.), Flora Europaea, vol. 2. Cambridge University Press, Cambridge: 324-326.
Chung K.F., Peng C.I., Downie S.R., Spalik K. & Schaal B.A. (2005) Molecular systematics of the trans-Pacific alpine genus Oreomyrrhis (Apiaceae): phylogenetic affinities and biogeographic implications. Amer. J. Bot. 92: 2054-2071. [available online at: http://www.life.illinois.edu/downie/Oreomyrrhis.pdf]
Clement E.J. & Foster M.C. (1994) Alien plants of the British Isles. BSBI, London: XVIII + 590 p.
Dihoru Gh. (1976) Differences between Chaerophyllum and Anthriscus. Rev. Roum. Biol., Biol. Veg. 21(1): 7-9.
Fröberg L. (2010) Chaerophyllum. In: Jonsell B. & Karlsson T. (eds.), Flora Nordica, vol. 6. The Swedish Museum of Natural History, Stockholm: 199-206.
Heath P.V. (1994) Commentary on the proposal to conserve Chaerophyllum Linné., Calyx 4: 98-99.
Knees S.G. (1997) Chaerophyllum. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 5. Cambridge University Press, Cambridge: 399.
Lambinon J. & Verloove F. (avec coll. Delvosalle L., Toussaint B., Geerinck D., Hoste I., Van Rossum F., Cornier B., Schumacker R., Vanderpoorten A. & Vannerom H.) (2012) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Sixième édition. Jardin botanique national de Belgique, Meise: CXXXIX + 1195 p.
Piwczyński M., Puchałka R. & Spalik K. (2015) The infrageneric taxonomy of Chaerophyllum (Apiaceae) revisited: new evidence from nuclear ribosomal DNA ITS sequences and fruit anatomy. Botanical Journal of the Linnean Society 178: 298-313.
Slavík B. & Slavíková (1997) Chaerophyllum. In: Slavík B. (ed.), Kvĕtena České Republiky, vol. 5. Academia, Praha: 284-295.
Spalik K. & Downie S.R. (2001) The utility of morphological characters for inferring phylogeny in Scandiceae subtribe Scandicinae (Apiaceae). Annals of the Missouri Botanical Garden 88: 270-301. [available online at: http://www.life.illinois.edu/downie/AMBG.pdf]