Roselle (Hibiscus sabdariffa, L.) is medicinal plant species producing anthocyanin, which are
flavonoids are water-soluble natural pigments. Two field experiments were conducted at the Experimental Farm
of EL-Quassasin Horticultural Research Station, Ismailia Governorate, Egypt during 2019 and 2020 summer
seasons. That, to define an appropriate vernalization types and gibberellin rates as well as their combinations for
achieving an early flowering and shortening of plant life, a better plant growth, fruits and sepals yield and
quality of roselle. Vernalization treatments were seven types: without vernalization, vernalization at 4 or 10ºC
for one week, 4 or 10ºC for two weeks and 4 or 10ºC for three weeks. Gibberellin treatments were three rates:
control, 100 and 200 ppm. The result of the research revealed that the early flowering date and the shortest
duration from sowing to reach the harvest was observed from the pre-sowing cold treatment of seeds at 10ºC for
three weeks followed by two weeks with no significant difference between them compared to the other
vernalization treatments under study. The same two treatments produced the highest values concern fruit
number and weight per plant, sepals yield per plant and per feddan as well as anthocyanin content. Using GA3 at
200 ppm reduced number of days to flowering and harvest compared to the other rates and control. The tallest
plants, more branches and fruit number per plant, heaviest fruits and sepals per plant and higher chlorophyll and
anthocyanin contents were obtained by the treatment of 200 ppm GA3 compared to the other ones under study.
The combined application of 10ºC for two weeks with GA3 at 200 ppm produced better responses and further
enhancement in plant growth, yield components, pigments and early harvest date. Therefore, it can be
recommended to apply it to the roselle plant under the same conditions.