I planted my Crimson Frost river birch in the swale in my back yard and it gets too much water. I need to move it up the hill just a bit and need to know when is the best time to transplant it. We live in Wentzville, MO.

Wait until the beginning of May or until all threat of frost is gone. Trees do best when transplanted after frost in the springtime. Be sure to properly water in the tree when transplanted and water good at least once a week until it takes. I am surprised that your river birch "gets too much water". These are water loving trees. I can't overwater mine enough. They grow much faster when watered a lot. In the summertime during very dry periods I leave my garden hose turned to a fast trickle in the 3 different clumps around my yard that I have and they just thrive. Your trees should not be very big to properly transplant either. Be sure that you dig a big enough hole to properly get all the roots when you take them out. If the trees are bigger I'd rethink moving them as it could kill them if not properly done right.

Well, the tree is in the bottom of a swale where water from my neighbors' yards drains through and the water kind of gets blocked by the tree and doesn't allow good drainage. I'm just wanting to move it up a few feet to allow water to drain by, but leave it close enough that it gets plenty of water. We have a sprinkler system and I'll make sure that zone puts plenty of water on it. The tree is 10'-12' right now. It hasn't grown much since we bought it.

I have always heard fall or early spring.

Yes, I think the trees need moved. Apparently they are getting too much water where they are now. Surprised they hasn't gotten bigger. Just wait until after they get moved. The clump I planted a year ago have more than doubled in height. Once they catch on they grow quickly. I planted a 7 tree clump that were no bigger than me and now 5 1/2 years later they are at least 30' tall. I do have a green thumb you could say.