Q.redbud tree has never flowered
My 3 year old redbud tree has never flowered. The leaves are healthy. What’s wrong? We planted a bare rooted redbud tree in a semi-shade spot. It’s now about 4 feet tall and seems healthy. I wonder if the tree has to reach a certain age before it flowers. Does it need fertilizer?

Your redbud probably isn't mature enough to bear blooms yet. They take about 4-5 years before they are of blooming age.
For more information on the care of redbud trees, please visit the following link:
https://www.gardeningknowhow.com/ornamental/trees/redbud/caring-for-redbud-trees.htm
For some fertilizing guidelines, check out the following link:
http://www.garden.org/searchqa/index.php?q=show&id=19668&ps=38&keyword=barrel%20garden