I've always loved Mimosa trees. So tropical looking. They remind me of the sensitive plants I grew from seed when I was little - touch the leaves and they folded up. Mimosa leaves do close up at night and when it rains, but not when you touch them. Anyway, they are just so tropical looking and the flowers almost look like some sort of fancy birds perched on the branches. We planted one quite a few years ago. In this zone, it isn't uncommon for them to died back to the ground the first few winters. Ours has stayed up for the last couple of years, and just this week it had its first flowers. I can't wait until next year when there are more. One thing we did find, is that you need to get seed from a local source if you live in the north to have the best chance of success. I just found out that it is a legume (such a big legume) and is native from Iran to China.
Flowering takes place over a long period of the summer and early fall on this smallish tree. The flowers are odd in that they have no petals, just lots of stamens. The flowers seem to be attractive to bees, butterflies and hummingbirds, though I can't say for sure who likes my 3 blooms since they are up so high. Once you have flowers you will also start to find baby mimosas in various places in your garden.
Flowers can be pink (what seems to be most common) or white or combinations thereof. There is a newer cultivar called 'Summer Chocolate' that has reddish brown foliage, but it hasn't been especially hardy here and is still quite expensive. No matter which sort you have, a Mimosa tree will make nice dappled shade for hostas or just a comfortable chair.