The Maximilian sunflower (Helianthus maximiliani) used to be the last perennial, with the exception of monkshood, blooming in my garden in October. Admittedly, it can grow to 10 feet and holds most of its flowers very close to its stalk, for a decidedly gangly look. In my flowerbed, the lanky latecomer also tended to slouch against nearby plants or sprawl at somewhat drunken angles, since I never got around to staking it.
I loved the plant anyway, for its rustic good looks and simply because there are so few other flowers blooming in mid-autumn here. I've heard that this particular sunflower can be invasive in warmer climates. Although it would self-sow a bit in mine, it never became a problem and, in fact, eventually died out. That could be due to my garden harboring some considerably more thuggish perennials, such as marshmallow and especially hops. Also, here in zone 5, "Max" probably never got much of a chance to sow seed before freezing weather set in.
Like the Jerusalem artichoke, the Maximilian sunflower grows from small edible tubers which can reportedly be cooked and eaten like potatoes. (Since we always had plenty of potatoes and less sunflowers, I never tried them!) Those tubers make the plant perennial in USDA zones 4 to 9.
Its narrow leaves can reach up to 10 inches in length on the lower part of the stem, but taper to about 2 inches up top. They are a favorite food of Silvery Checkerspot and Border Patch butterfly larvae. The short flower stalks, which spring from the axils of those leaves, are usually produced only on the top half of each towering stem. The yellow blooms can vary in width from 2 to 5 inches.
This sunflower, which originated on the Great Plains, is named for a German prince, Maximilian Alexander Philipp of Wied, who toured those plains in the 1830's. Due to the fact that he was the 8th of 11 children, Maximilian probably concluded that there wasn't much point to his taking up politics. He went in for science in a big way instead and studied both the native plants and native peoples of states from Missouri north to Montana.
If you don't like the attenuated look of the wildflower named for him, you can cut it back to about two feet around the beginning of July to keep it shorter. Or you can give it a fence against which to drape its lanky frame! The cultivar "Lemon Yellow" has paler flowers, while "Dakota Sunshine" blooms earlier than the species type-usually in August.
Because this is a perennial sunflower, you might be able to improve the germination of its seeds by storing them in the refrigerator for one or two months before you plant them. You'll have to grab them before the finches do, however, as those birds are said to be particularly fond of these seeds. Birds, I have discovered, know a sunflower when they see one-no matter what deceptive guise it might take!