GROWING DEVELOPMENT PHASES of EVENING PRIMROSE PLANT (Onothera spp.).

The evening primrose plant cycle was divided into six successive phenological phases: germination, rosette, stem elongation, flower differentiation, flowering and fruit maturation. Between two successive phases a boundary was defined by an easy observable morphologic characteristic. This description was created for helping farmers and technicians to better manage their evening primrose crops. Phase 0. Germination. This phase started when seeds were sown and ended when cotyledons were above ground and had emerged. Phase 1. Rosette. The presence of cotyledons above ground marked the beginning of this phase and ended when the stem started to extend. This phase included the initial part of the leaf differentiation. Leaf buds at the top were counted as pairs. Phase 2. Stem elongation. This phase started when the stem at its base was at least 2.0 cm long and clearly started to elongate ending all plants their apparent prostrate position. Phase 3. Flower differentiation. This phase started when flower buds were first visible at the tip and ended when the first flower opened. Phase 4. Flowering. The first flower open marked the start of this phase, which ended when the last flower opened. Phase 5. Fruit maturation. This phase started when the last flower opened and ended when the plant died and included the last part of fruit and seed maturation, which started at the middle of flowering phase. At the beginning of this phase it was observed that seeds of the first capsules (bottom of the flower spike) started to turn from white to brown. These capsules, after the first third of this phase, started to open and release black seeds. This process continued upwards from the last mature capsule to the next capsule. Dead plant was defined when the whole length of the flower spike turned to brown and dry and the last capsule opened.