How about these fall blooming Colchicums popping out of the Lysimachia? Easy as pie, you just have to buy the bulbs early! Fall "crocus" produce lots of leaves in the spring, die off for the summer, and the flowers emerge (naked) in September.
Sweet Autumn Clematis
What's that climbing in the birches? Clematis? YUP, again a fall blooming species, ternifolia (used to be paniculata among others). They sprawl up the arbor and off into the branches. It looks like a white birch in bloom. GOTCHA
....and just one more mention of the fantastic Salvia species and varieties. Bluer than blue and hummingbird magnets! Just a few to note, uliginosa (Bog Sage), guaranitica 'Argentina Sky', and 'Indigo Spires'
............pray for rain............CU next time.............got your bulbs ordered? Don't forget paperwhites,