The life cycle of a sunflower consists of germination, growth, flowering, seed development and death. Sunflower plants complete an entire life cycle in a single growing season. While many varieties of sunflower exist, the basic phases of the life cycle remain the same.
Sunflowers are annual plants known for producing large and distinctive flowers. Plants germinate from seeds five to 12 days after planting. Sunflower germination requires warm soil temperatures and moist conditions. Temperatures between 70 to 78 F produce optimal sunflower growth and plants typically require about 30 days before the development of the flower bud becomes noticeable. Flowering occurs approximately three weeks after the bud first becomes visible.
Seeds develop once the sunflower finishes blooming and continue to ripen for approximately 30 days. Once ripe, seeds begin to dry and are gradually shed from the bloom. The rest of the sunflower plant begins to wane during this phase of its life cycle and leaves typically yellow and wilt. Growth ends after shedding the ripe seeds, and the plants begin to die when temperatures fall below 28 F.
Sunflowers are resistant to both heat and drought and have a reputation for being hardy and easy to grow. Sunflower plants do best in full sunlight and require long hot summers to flower well.