The sunflower plant is an exciting study in how nature has developed efficient ways to grow and protect itself. Growing sunflower seeds as a class project or with your children can teach everyone about the life cycles of plants and the unique characteristics of sunflowers.
The first stage in the life of a sunflower is germination, which can take between two and 10 days. The seed shell softens in the spring rains and beings to shoot roots out in order to anchor the seed. As the ground gets warmer, and the roots give the plant nutrients, a sprout shoots toward the top of the soil. Once it breaks through the ground, it is vulnerable to attack from hungry birds and animals, as well as extreme weather.
The seedling stage begins when the sprout has small leaves, no longer than 1 1/2 inches. At this stage the sprout grows taller and starts to produce more leaves. The seedling stage only lasts about two weeks after the sprout pops through the ground.
The vegetative stage means the sunflower stalk has leaves that are longer than 1 1/2 inches. This is when all the main growth occurs, with the stalk thickening and growing taller, and producing leaves at regular intervals on the stalk.
This stage begins as soon as the bud begins to show at the top of the stalk. Once this happens the sunflower starts to preform heliotropism, which means the leaves and bud move to follow the course of the sun throughout the day. This ensures they receive the most sunlight available, as well as using the heat to dry morning dew and reduce the risk of fungus. During the night the plants only face east.
Once the bud begins to open, the flower remains facing east and no longer performs heliotropism, although the leaves sometimes continue to move according to the sun's position. The complete opening of the bud can take up to seven days, and proceeds from the outside toward the middle of the sunflower. Soon after the flowering is complete, the ray flowers on the outside of the bloom begin to wilt. The head of the sunflower bows, which forces the rain to run off of it rather than gathering, and reduces drying time and fungal infections.
The final stage of the sunflower plant allows the seeds to fall and become planted in the ground. At this time the back of the sunflower's head begins to turn yellow and then brown. The petals and leaves turn brown and fall off. The stalk and head begin to dry out and eventually all of the seeds are loosened and fall out.