Sulla is a biennial forage legume native to the central-western Mediterranean Basin and has increasing interest for regions with Mediterranean-climate. The Italian germplasm is a reservoir of variation for important agronomic traits. This study aimed to support breeding programs by investigating patterns of agronomic, adaptive and morpho-physiological variation among ecotypes collected from the three main Italian regions of species cultivation: central Italy, and the two islands of Sicily and Sardinia. Forage yield and morpho-physiological traits were evaluated at a site with Mediterranean climate in Sicily. Forage yield and cold tolerance in a cold-prone site of northern Italy were also assessed, to locate useful germplasm for widening crop resilience and climatic adaptability. Collection regions, and ecotypes within regions, differed for total forage yield and final plant survival, but their responses were subjected to interactions with test location. Specific adaptation dominated the adaptive responses of ecotypes and elite commercial varieties. Ecotype adaptation to cold winter was associated with latitude and, more specifically, the extent of cold stress in collecting sites. The ecotype collection region had a bearing also on morpho-physiological characteristics. A few ecotypes from central Italy performed outstandingly with respect to elite varieties, displaying wide adaptation across cold-prone and drought-prone environments.