Answer: Cosmos is a heat loving plant and takes a number of weeks to come into bloom -- sometimes it begins blooming in mid to even late summer when started from seed in the garden. I suspect you will have to be patient a little longer! In the meantime, do not trim it or pinch it. Make sure it has full sun and adequate fertility but do not give it an excess of nitrogen because that will encourage more foliage and fewer blooms. Once it starts blooming it will continue until frost, so the wait is worth it!
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