Like all member of the Ipomoea family, all parts of the plant are poisonous, which accounts for the unchewed leaves. Moonflowers take a long time to bloom from seed, but during the three months of growth that precede flowering the leaves weave their way through my inexpensive wire garden fence and turn it into a solid wall of green.
Moonflower is not a self seeder here in Massachusetts, since frost usually hits the plants before the seeds are mature, though about one year out of five I am able to collect a few seeds from the earliest blooms. And in order to be sure of September bloom Moonflower should be started indoors, about
the same time as tomatoes, which means late March for me. In fact, I treat my Mooonflower seedlings just like my tomatoes -- I start, harden off and transplant them into the garden at the same time.
It's a little bit of work compared to some of the prolific self sowers I have already picked for my top five, but once you've stepped into a September garden full of Moonflowers in bloom, you'll understand why this flower makes the list.