frostweed said:Yes, they bloom at different times during the season. The plant will get leggy during the summer.
If you cut it back two months before the date you want them in bloom, you should have blooms for the fall butterflies.
But don't forget that the butterflies will be around spring and summer as well as fall. 
Thank you for this additional information and for the reminder to grow different nectar producing plants. I will make a note to trim it back in July so as to have blooms during the Fall Monarch migration.
Yes, in my small garden you will see large old fashioned Red Pentas, Verbena bonariensis, butterfly bush, lantana, tropical milkweed (all the little flying things feed off these blooms), Salvia coccinea 'Lady in Red' and what has turned out to be a long blooming and excellent nectar producer, the little milkweed A perennis. My garden is small so I have to be selective in what I grow while attempting to get the most bang for the buck.
I like to try something new each season and this is one of two 'new to me' plants I'm trying this year. Quite curious about this plant as it is reputed to be hardy and attractive to the butterflies. Thanks again for your help.
Myles
