Cucumis myriocarpus

Cucumis myriocarpus Naudin (S Afr.) – A very rare and ephemeral alien. Formerly occasionally recorded as wool alien in the valley of river Vesdre, at least between 1895 and 1955 (Verloove 2006). As such, it was also known from several other European countries, for instance from Sweden (Karlsson 2010), the British Isles (Clement & Foster 1994) and Central Europe (Scholz 2008). Two individuals were found in 2018 in Bossuit (Avelgem) on the banks of river Schelde, along with Cucumis dipsaceus. Both species appeared after reinforcement works. Accompanying species were, among others, Cucurbita pepo, Helianthus annuus and Solanum lycopersicum. These species can be associated with sewage works (food refuse) or birdseed. Cucumis myriocarpus and C. dipsaceus are also included in ornamental fruit mixtures for fences. The exact origin of Cucumis myriocarpus in this locality, however, remains uncertain. According to Clement & Foster (1994) it is possibly also an impurity in commercial birdseed mixtures which might also explain its recent occurrence.
Cucumis myriocarpus has become a naturalized weed in warm-temperate and subtropical regions across the world, also in the Mediterranean, for instance in the Iberian Peninsula (see Molina 2017 for an overview). In Australia it is an important summer annual weed of agricultural fields (Shaik & al. 2017).
With its deeply lobed leaves with rounded sinuses Cucumis myriocarpus superficially resembles Citrullus lunatus. In the absence of mature fruits both can be intermingled. Cucumis myriocarpus, however, has much smaller (petals ca. 5 mm), bright yellow corollas, unbranched tendrils and leaf margins are markedly undulate. Compared with the other Belgian representatives of Cucumis it has very small, aculeate pepos that are ca. 20 mm across. Also, it has smaller corollas and deeply palmately divided leaves.

Selected literature

Clement E.J. & Foster M.C. (1994) Alien plants of the British Isles. BSBI, London: XVIII + 590 p.

Karlsson T. (2010) Cucurbitaceae. In: Jonsell B. & Karlsson T. (eds.), Flora Nordica, vol. 6. The Swedish Museum of Natural History, Stockholm.

Molina Molina D. (2017) Primera cita de Cucumis myriocarpus Naudin subsp. myriocarpus (Cucurbitaceae) para la Comunidad Valenciana (España). Revista BV Publicaciones Científicas 6: 95-99. [available online at: https://www.biodiversidadvirtual.org/taxofoto/sites/alienplantsbelgium.b...

Scholz H. (2008) Cucurbitaceae. In: Conert H.J., Jäger E.J., Kadereit J.W., Schultze-Motel W., Wagenitz G. & Weber H.E. (eds.), Gustav Hegi Illustrierte Flora von Mittel-Europa Bd. 6, Teil 2A. Weissdorn-Verlag, Jena: 36 pp.

Shaik R., Burrows G., Urwin N., Gopurenko D., Lepschi J.B. & Weston L. (2017) The biology and management of prickly paddy melon (Cucumis myriocarpus L.), an important summer annual weed in Australia. Crop Protection 92: 29-40. [available online at: https://www.researchgate.net/publication/309372200_The_biology_and_manag...

Verloove F. (2006) Catalogue of neophytes in Belgium (1800-2005). Scripta Botanica Belgica 39: 89 p. [available online at: http://alienplantsbelgium.be/sites/alienplantsbelgium.be/files/tabel_2.pdf]