Protected cultivation of hybrid English cucumber (Cucumis sativus L.) offers a route to substantially higher and more consistent yields than open-field production, but on-farm evidence documenting week-to-week yield escalation under commercial polyhouse conditions in South India remains limited. This case study reports harvest-wise production data from a 1-acre naturally ventilated polyhouse at Alangur, Kolar district, Karnataka, sown with a gynoecious hybrid cucumber on 3 July 2026 at a spacing of 1 ft (plant-to-plant) × 2.5 ft (row-to-row), giving a plant population of 8,421 seed points per acre. Germination reached 91.6% (7,715 established plants). Picking commenced on 10 August 2026 on a 2-day harvest interval. The first harvest (10 August) yielded 1,198 kg of marketable fruit; the second harvest, two days later (12 August), yielded 2,001 kg from approximately 11,000 fruits at a mean fruit weight of ~180 g — a 67% increase over the first picking and roughly double the customary single-day benchmark yield of ~1 tonne reported for polyhouse cucumber blocks of this size. Non-marketable (cull) fruit was negligible (7 kg), giving a marketable fraction exceeding 99.6%. The yield surge coincided with correction of an observed potassium deficiency, sustained drip fertigation at 200 mL plant⁻¹, and active scouting-based management of Spodoptera sp., thrips and leaf miner. We situate these on-farm observations against the published literature on protected-structure performance, plant density, potassium nutrition and pest management in greenhouse cucurbits, and propose that the second-harvest surge is attributable to the coincidence of peak early-cycle fruit set, corrected potassium nutrition and stable microclimate rather than to any single factor in isolation. The results support naturally ventilated polyhouse cultivation, tight plant spacing with rigorous canopy and nutrient management, and short harvest intervals as a practicable route to high, early-cycle marketable yield in hybrid cucumber under Karnataka's agro-climatic conditions.