Euphorbia hypericifolia Linnaeus (1753: 454)

Mifsud, Stephen, 2018, Contribution to the flora of the Maltese Islands: Euphorbia subg. Chamaesyce and Euphorbia exigua s. l. (Euphorbiaceae), Phytotaxa 372 (2), pp. 153-166 : 159-160

Euphorbia hypericifolia Linnaeus (1753: 454) [ Fig.1E ]

Origin: tropical and subtropical America ( Steinmann et al. 2016, Tropicos 2017).

Occurrences in Europe and the Mediterranean area: Aegean islands, Greece, Crete, Belgium (Raab-Straube & Raus 2015, Euro+Med 2006–2017), NE Sicily ( Sciandrello et al. 2016) and Spain (Raab-Straube & Raus 2015).

Introduction in Malta: contaminated soil of imported plants or trees used to decorate roads, traffic islands, hotels and public spaces.

Habitat: Naturalised in soil for embellishment at roadsides and traffic islands, large planters, outdoor gardens and terraces. So far not observed on or beside curbs or paved ground.

Invasiveness: Weakly invasive, spread readily within the area it occurs but it is not able to disperse. Increased records during last three years are likely cases of new introductions. Not yet encountered in natural ecosystems, strictly urban species.

First record: The present record (Marsa, October 2009) is the first one for the Maltese islands.

Distribution: Scattered individuals in traffic islands (Manuel Dimech Street, Qormi), soil of embellished areas (e.g. il-Menqa, Marsa; Paradise Bay Hotel, Mellieħa) and large potted plants (Dragonara, St. Julians)

Flowering: June–December.

Morphological observations: Suberect to erect habit with glabrous leaves and flowers. Leaflets variable in shape and of little diagnostic value, ranging from broadly ovate to narrow-lanceolate with a shallowly serrulate margin, usually lacking red markings. It is closely related to E. nutans Lagasca (1816: 17) and possibly confused with it locally, although the presence of both species in Malta is not excluded. E. hypericifolia differs from E. natans in having fruit up to 1.4 mm high and green (1.5–2.0 mm reddish or green in E. nutans ); completely glabrous (slightly pubescent at the leaf nodes and base of stem in E. nutans ) and usually some stipules are deltate and conspicuous (mostly vestigial or linear in E. nutans ).

Chromosome number: 2n = 42 ( Benedì & Orell 1992).

Figures

FIGURE 1. Photos of stipules (left), fruit capsules (centre) and seeds (right) of:A: Euphorbia serpens (EUP03); B: Euphorbia chamaesyce (EUP05); C: Euphorbia maculata (EUP15), D: Euphorbia prostrata (EUP 11); E. Euphorbia hypericifolia (EUP 20). Scale bar = 2mm.