Silkvine in the Segre’s riverside forests: what a 2007 cut-stem trial found
Botanists at the University of Lleida reported in 2009 that silkvine, an ornamental climber, was spreading through riverside forests on the lower Segre and that its cut stems could sprout weeks later.
What the study did and found
The paper, “Comportamiento invasor de Periploca graeca en bosques de ribera del río Segre (Cataluña)”, appeared in Spanish in 2009 in the proceedings of a weed-science congress in Lisbon (Conesa et al., 2009). Its four University of Lleida authors had found 12 silkvine patches covering 0.7 ha in the city’s Parc de la Mitjana.
In the study, 72 cut stem sections 35 cm long were laid on peat outdoors and potted in weekly batches over eight weeks. Eleven (15%) sprouted and 27 were alive at the end; none left lying six to eight weeks survived (Conesa et al., 2009).
Why it is cited
The referring page is Wikibooks’ Flora of New York page on the Gentianales, where a footnote cites the record for silkvine being “listed as invasive in Northeastern Spain” and rooting from “small pieces of stem”.
The footnote matches the paper’s broad message but stretches two points: the paper is a field report and pot trial, not an official list, and its 35 cm sections were scored for shoots, with no rooting data (Conesa et al., 2009).
The evidence is one small pot trial of 72 cuttings from a single park, with no statistical tests, presented as first results; the paper’s survival percentages also divide by 74 rather than 72 (Conesa et al., 2009).
Later work points to continued spread: a 2016 bachelor thesis mapped 67 populations on the lower Segre in 2015, against 36 affected points in 2006 (Hidalgo i Jiménez, 2016), while Catalonia’s EXOCAT database still rates silkvine as not established (CREAF, n.d.).
The topic today
Silkvine is on neither Spain’s catalogue of invasive alien species nor the EU list of 114 species of Union concern (European Alien Species Information Network (EASIN), n.d.). Lleida city council still clears it from La Mitjana (Ajuntament de Lleida, 2025).
For the current picture, see our explainer Can Cut Silkvine Stems Sprout? The 2007 Lleida Trial.