One of the easiest flowers to grow, sunflowers are some of the most rewarding too. Many varieties of sunflower exist, ranging in color and height, but they all love full sun exposure. Most have massive yellow flowers and strong, tall stems that can reach up to 6 feet. Scatter their seeds in the spring for summer blooms and watch them reseed the following year! Birds, squirrels, bees and butterflies will enjoy your sunflowers just as much as you will. Zone 4-9.