david's garden seeds sunflower tall single stem mammoth grey stripe 5193 (yellow) 50 non-gmo, heirloom seeds david's garden seeds tall single. with huge flowers (often 10 to 12" inches across) these garden giants are developed for seed production (sunflower oil, bird seed, etc.) remember, these are the ones that grow from 8 to a whopping 12 feet tall, so unless you're planting them alone, scatter them throughout your meadow, or use them as a background screen. kids love watching them grow so fast and so tall, and of course, they're magnets for songbirds. special note! these have to be direct sown--as do most sunflowers. they do not do well transplanted. you need to space them at least 12 to 18 inches apart. david’s garden seeds is a veteran owned business that has been providing quality seeds since 2009.