Spring seep should remain a relatively constant 52 degrees.

Elderberry could be a problem. It will happily grow everywhere and become as big as you allow it to be - and it will grow fast! I recommend against it. Don't see that blue berries should be a problem - at least not if you keep them pruned. /Hans Olav

You'll probably get some differing opinions on this but I myself would go for it. The amount of water isn't going to matter nearly as much as the quality (very low nutrient/mineral content/low to neutral ph) and the medium you use. I would alter the mix to be a little less water retentive, use more sand. I might also give it a bit more drainage. As long as it's full sun and the water doesn't actually disturb roots or really pool for very long periods of time I'll bet you'll be ok. I had a bog that got lots of runoff and groundwater, not ideal because it's hard to keep conditions constant, but do-able. Remember, fertilize the lawn once and it runs in there you lose the whole bog in one fell swoop. I'm assuming CP or similar acid bog since you mentioned low nutrient.

We just got done re-doing a small boulevard garden into a larger rain garden, which is meant to collect the rainwater coming off of our hill. We are on a corner so this is just the beggining. John dug the plants we had there out, kept some and gave away others. We had lots of ribbon grass to give away. He dug the garden lower than the sidewalk and added a berm using the extra soil firmed down. It has been keeping the water from running off for the last week. We are moving in natives from our garden and will trade for and buy more. It is a simple form of a rain garden. .