This study addresses the challenge of drought stress in ornamental plants by evaluating the drought response of Cuban oregano (Coleus amboinicus Lour.) and the potential of sea fennel (Crithmum maritimum L.) extracts as biostimulants to mitigate the effects of water deficit. Conducted in a greenhouse under two irrigation regimes, full irrigation (100% water replacement) and deficit irrigation (50%), the research applied foliar treatments of sea fennel extracts prepared via aqueous extraction (WE) and alcoholic extraction (AE) at various concentrations. Drought stress significantly reduced total dry biomass by 48%, leaf number by 33%, and leaf area by 57%, severely impacting both aboveground and root growth. Biostimulant treatments alleviated these negative effects, with alcoholic extracts at 2.5 mL L⁻¹ showing the greatest efficacy by increasing biomass by approximately 60% and restoring leaf area to levels comparable to fully irrigated plants. Aqueous extracts provided moderate improvements. Drought induced an increased root-to-shoot ratio, indicating adaptive biomass allocation, while SPAD values and gas exchange parameters (net photosynthesis and stomatal conductance) declined under stress but improved with biostimulant application, especially with AE treatments. Photosystem II efficiency (Fv/Fm) confirmed stress but showed partial recovery in AE-treated plants. Additionally, WE at 5 mL L⁻¹ enhanced anthocyanin and amino acid accumulation, suggesting metabolic adjustments to drought. Overall, alcoholic sea fennel extracts demonstrated superior potential as sustainable biostimulants to enhance drought tolerance in ornamental plants.

The ornamental industry encompasses a wide range of species cultivated for their aesthetic value, including floriculture crops, ornamental and turf grasses, trees, and shrubs. In Italy, in particular, this sector represents a significant component of the agricultural economy, with an annual wholesale production value of approximately EUR 2.6 billion. Despite its economic importance, the industry has recently faced challenges related to the COVID-19 pandemic and increasing international competition. Moreover, ornamental production is highly water-demanding, making water availability a critical concern under climate change scenarios. The future competitiveness of ornamental sector depends on its ability to adapt to environmental and market pressures through sustainable cultivation practices, diversification with value-added crops, and improved post-production management. This study investigates the potential introduction of non-endemic wild or underutilized species as innovative ornamental crops for EU markets. While economic evaluation will be essential prior to commercialization, the current focus is on identifying promising species and outlining strategies to optimize the production chain. These approaches aim to enhance the sector’s resilience, align with sustainability goals, and foster innovation within the Italian and Mediterranean ornamental industry.