I my area Alberta's seem to always get dead spots on them eventually and why I have steered clear of them. Big Maples can look nice, but I wont risk getting one with those awful helicopter seeds...lol..I dont want 1000's of maples. I have an Elderberry and in bad winters they will die to the ground. BUT THEY GROW LIKE A WEED! Just like a Butterfly Bush. Mine every year gets over 6 foot tall no matter what. I wouldnt suggest it for your front of your home with how well structured you have everything. I am sure you will be dissapointed in it. I enjoy mine located in the back yard and gets a ton of sun and has the room to do whatever it wants. Might also constantly reach for the sun out front, would be my guess. I have a smaller variety of dark leaved ninebark that gets about 5 foot tall. Sorry I am not sure what type it is, but I know it is not a diablo which I believe gets bigger than mine. I have never had a mildew issue with it, but could be due to it gets alot of evening sun also. I think it could be a good choice for that spot along with the smaller variety of dark leaved weigela you have mentioned. My final comment would be to consider a laceleaf weeping Japanese Maple for that spot if you are looking for that color scheme. But looks like it could be a little tight for that spot and you might have to make that spot a litte wider from the house. BTW everything looks great!!

I have two diablo ninebarks too. I love this plant. I'm really amazed that it got that infected and from the picture I would say that yes, it is downy mildew. Though, when you said that the leaves turn black and die, that made me think of blight. Diables have a tendency to get too bushy which could impede air circulation so I judiciously prune to allow better air circulation. Maybe that's why none of this has happened to my shrubs yet. You might want to cut a diseased stem and take it to your local cooperative extension where someone who is an expert can tell you what it is or test it to find out exactly so that you will know how to treat the disease properly. As far as moving this plant that would be impossible considering the size and the fact that it is pretty deep rooted. What you might want to do is layer a stem still attached to the plant to start new plants. Simply pull lower stems down to the ground, remove the leaves in the middle of the stem and cover that portion with soil (you might have to anchor it with a cloths pin or a rock) leaving the tip of the stem (with leaves) sticking out of the ground. It will root and if you have to eventually replace the shrub you will have a copy to replace it with - that is, if the plant isn't genetically inferior, which is something that I have been studying about lately. Just like all living things, sometimes there will be genetic differences between shrubs of the same species. This is more likely if you've got the shrubs from the same place. Though unlikely, it could be a possibility. Good luck.

What is the soil like and what, if anything, did you do to amend it? My 'Summer Wine gets shade starting at 3-4 ish this time of year and I don't recall seeing that shade of green lately. Might have when I first planted it, but I don't recall. As bboy said, you have purple and that's a good thing. tj

Thanks for the tip! I've definitely done some searching for powdery mildew remedies, but I also wanted to confirm if all the dead branches were caused by powdery mildew or something else. Does that sound plausible, or is there some other search term I should be using here? Sorry if this is a stupid question. I'm not a very experienced gardener.