Sunflower seeds sprout in seven to 10 days, and the plants mature and produce seeds in 80 to 120 days, depending on the type of flower, according to Burpee, a seed distributor. Plants need to be about 2 feet apart.
Sunflowers grow tall quite rapidly, sometimes stretching up to 6 feet high in only three months, according to Burpee. Staking the plant by tying it to a stiff support relieves stress on the branches and prevents blooms from breaking off the stem. Mature sunflower plants produce edible seeds that are harvested when the backside of the flower becomes yellowish-brown and the flower head begins to droop.