Calendula, Linnaeus, 1753

Simão, Inês, Reyes-Betancort, J. Alfredo, Talhinhas, Pedro, Morais-Cecílio, Leonor & Silveira, Paulo, 2024, Taxonomic revision of the genus Calendula (Asteraceae) in the Canary Islands, Phytotaxa 640 (2), pp. 125-160 : 138

Key to the species of Calendula in the Canary Islands

1. Cymbiform achenes with a more or less developed ventral wing; disc florets at least 60 ........................................ 2. C. officinalis

– Cymbiform achenes without a ventral wing; disc florets up to 50, more frequently between 15–25 .............................................. 2

2. Outer achenes rostrate or bialate with incise-dentate lateral wings, never trialate ...................................................... 1. C. arvensis

– Outer achenes rostrate and trialate with entire to sub-entire lateral wings ....................................................................................... 3

3. Capitula diameter (0.7) 0.9–1.1 (1.3) cm; rostrate achenes (4.9) 6.2–10.6 (13.5) mm long; leaves strictly linear-oblong ................ ...................................................................................................................................................................................... 4. C. sventenii

– Capitula diameter (1.4) 1.7–2.7 (3) cm; rostrate achenes (10.4) 13.7–22 (25) mm long; leaves ovate to oblong, less frequently oblanceolate .................................................................................................................................................................. 3. C. ricardoi