Does constant or changing light give the best rooting of hibiscus cuttings of two sizes?

•Limited light requirement for rooting allows for 5 weeks propagation of hibiscus in vertical table system under LED lamps.•Low light before root emergence conserve water while higher subsequent light promotes photosynthesis and root growth.•There is a linear relationship between light integral and rooting within each light protocol (constant or increased light).•76 → 151 µmol m−2 s−1 light treatment gave the best rooting, combining water conservation with boosting of photosynthesis.•7 cm cuttings had higher rate of photosynthesis, more carbohydrates, and more root dry matter than 10 cm cuttings.