Mammoth Grey Stripe Sunflower | Helianthus annuus | Ecologically grown | Annual | Heirloom Mammoth Grey Stripe Sunflowers are huge, reaching heights of up to 10 feet, and their blossoms measure between 10 and 15 inches across. They bloom in the later part of summer and produce huge numbers of delicious-tasting seeds. Extremely alluring to songbirds. Companion plants: Bush beans, Squash, Cucumber, Corn, Lettuce, Any plant with aphids. Far from: Potato. Planting tip: Direct sow outdoors end of May. Harvesting tip: Harvest when seed heads dry on their stems. Put a brown bag over the flower to secure it away from squirrels and birds.