A two‐year field trial was carried out to identify the most effective concentration of colchicine (Colch) for seed priming in spinach ( Spinacia oleracea L., cv. Desi Palak) with the aim of improving crop performance and resilience under changing environmental conditions. The study revealed that seed treatment with 0.07% Colch significantly enhanced morphological, anatomical, fluorescence, and biochemical characteristics of spinach, whereas higher concentrations negatively affected growth. In comparison to the untreated control, the 0.07% Colch treatment resulted in notable increases in germination rate (20.3%), plant height (62.2%), number of leaves plant −1 (51.4%), leaf area (63.6%), crop growth rate (54.3%), and leaf yield (25.9%). Positive effects were also observed on stomatal size (44.4%), stomatal index (23.1%), leaf thickness (81.5%), quantum yield of photosystem II (46.4%), chlorophyll content (49.7%), linear electron flow (74.4%), and the enzymatic activities of catalase (23.4%), superoxide dismutase (33%), and peroxidase (14.3%), along with antioxidant capacity measured in terms of 2,2‐diphenyl‐1‐picrylhydrazyl‐radical scavenging activity (28.3%). Moreover, the chromosomal count was doubled in plants treated with 0.07% Colch compared to the control, and polyploidy was cytogenetically verified, confirming its effectiveness in inducing genome duplication. Conversely, reductions were recorded in stomatal density (42.8%), nonphotochemical quenching (threefold), nonregulatory energy dissipation (twofold), hydrogen peroxide (31.5%), and superoxide anion levels (25.5%). Thus, the above findings demonstrate that 0.07% Colch seed priming can induce beneficial changes in the morphology, anatomy, physiology, and biochemical profile of spinach, providing practical implications for breeding strategies and sustainable crop development.