Helianthus annuus This American native is huge! Grows to 15ft+ tall, heavy yield, bright yellow flowers. Heads can be at times over 12 inches across. Easy to grow, high germination rate. World record holder! Sun to part shade. Heavy heads may require staking! At the end of the season you'll have a wondeful focal point to watch birds rest on the stalks and feast. 75 days. Growing instructions Start seed indoors 4-5 weeks before last frost in pots, or sow directly into the garden after danger of serious frost has passed. Cauliflower seed is more sensitive to the cold than its cabbage-family relatives. Cover seeds with 1/2 inch of fine soil. Once plants are two to three inches tall, thin to space plants 18 - 24 inches apart. Transplant indoor started seedlings after hardening off and danger of serious frost has passed. 10 to 14 day germination time. Keep soil moderately moist during germination. This sunflower is in hardy zones 5-9.