The American cranberry bush is primarily a ground cover. It sends out runners that take root along their length. The rooted runners then grow upright canes or branches. These uprights grow flowers and then produce cranberries. During the first two growing seasons after planting in your garden, encourage the plant to produce a lot of runners. In early spring of its third year of growth, prune the runners back to encourage them to produce more upright canes. Also prune uprights back at this time to encourage them to produce flowers and cranberries.
Remove any dead or diseased branches, whether growing upright or along the ground.
Use a garden rake to rake the runners not yet rooted along their length so they all face one direction.
Trim off one-third of the length of the runners.
Cut back the upright branches by one-third of their height.
Reposition the runners. Any runners that are not yet rooted along their length should be repositioned so they are evenly spaced around the plant.