This is not the best picture and that is not the most perfect Cornus canadensis flower of all time but it is flowering right now in the Northern Bog along the Main Trail in Fern Valley. That is something of an accomplishment. Bunchberry is a low creeping dogwood that is only listed as far south as USDA Zone 6; we are either a very high 7 (the general consensus), or a low 8 (my personal observation), and success with this plant is not common hereabouts.
We are growing it in a person made bog that we did a few years ago. To create it we excavated soil to a depth of about a foot, lined the excavation with a rubber pond liner, removed the middle of the bottom so that water could slowly drain in the event of prolonged periods of high rainfall (like this spring). Then we filled it with a mixture of sphagnum peat (both long fibered and standard horticultural) and quartz sand. We have been planting it ever since.
I am a person who goes to a lot of gardens and "bogs" were features that were quite hot for a while and may still be. This bog is working better than any of the other "created" bogs that I am aware of. We are developing a pretty good cover of Sphagnum moss, which is, of course, the predominant plant in most northern bogs, as well as the substrate in which the other plants grow. We have two cranberries, Vaccinium macrocarpon, that need to be pruned diligently lest they take over the entire bog. There are carnivores, both Sarracenia and Drosera. And there are a host of other northern species that are doing well so far: Twinflower, Labrador Tea, Rhodora, Leatherleaf, Crowberry, Aletris, Calopogon, Linnea, and, actually, a few more I am not remembering. You can't miss the bog; its abuts the left side of the main trail (by the Fern Valley sign across from the Parking Area) about 100' in from the road.