You are in a much warmer zone than I am, but in my garden, the red elderberry (Sambucus pubens /aka S. racemosa) blooms decidedly earlier than the American elderberry (S. canadensis), which has dark, purplish-red berries and is used for jam. I grow the former one for the birds. Are you referring to S. caerulea when you say "blue elderberry" or S. canadensis? We don't grow caerulea here.

I still have a good amount of non-native plants in my landscape, but I've decided to plant just native from now on. Without significant research of each and every nativar out there, and more that are introduced each year, there's just no simple answer to your question. Nativars have been known to spread or interbreed with local native plants displacing native flora. Sometimes the nativar can support local species, but sometimes not. It's a crapshoot. By planting naturally growing native spieces, it assuridly eliminates any possible negative impacts. I have Canadian elderberry in my yard. I consider it to be one of my most beautiful plants. Cultivated in the garden, it's much more stunning than in the wild IMO. I think the white flowers and red/black berries against green leaves are prettier than the dark leaves with pink flowers of the cultivars that you're considering, but again, that's just my opinion. I can appreciate you wanting a plant that gives a punch of color to an otherwise green landscape. Having said that, I often suggest to people that they not plant burning bush because it is invasive. They say to me that it is not invasive in their yard. I tell them that the birds eat the fruit and spread the seed to natural areas. They say they have never seen fruit on their plants. I say that the fruit is inconspicuous. My point is, you just don't know if the plants in your garden are invasive by simple observation.

You know I have only one American type, and it doesn't do well, go figure? Who the heck knows?? I'll tell you all I can. It is between houses so it only receives about half a day, maybe slightly more of sun. In ground, we have a clay loam with a pH of about 6.5. It is very nice soil. Every spring I put bagged composted manure around it. I put a small amount of Dynamite control release fertilizer. And once a month use an organic. Usually Holly-Tone. I fertilize my grass with Milorganite, so it probably takes that up too. It is now approved for garden use, but I only use it on my grass. I grow over 20 different fruits and veggies. Not worried if some gets in the garden. I mulch with leaves or straw, but often I scatter it with the lawn mower. It needs more right now. I should clear more of the grass around the plants. If I left the 2nd year canes I could probably get a bigger yield. But I'm good with the 5 pounds or so I get. Going back to the subject of this thread, the thought came to me that maybe in Florida it's nematodes, as the state is notorious for having them. The kind you don't want. Maybe that was covered already? I heard tomatoes are hard to grow there because of the nematodes, and maybe elderberries are susceptible to them? I don't know? Some plants are not. I cannot grow blueberries in my soil. The west side of the state is all sand and that is where the pH is low and they grow them. I'm on the east side. I do grow blueberries but in containers, and raised beds filled with pine bark and peat. I use sulfuric acid to lower pH of tap water, but usually use rainwater (pH of 4.7) for my blueberries. I have 10 plants. Most of the other elderberries I grow are ornamental. I grow a variegated euro, Black Lace, and Black Beauty. All do very well here in ground.

To be honest it’s barely visible and I’d just put it down to normal natural wear and tear. But I am curious about the circle of dead grass at the base. Is that a mulch or has a herbicide been used?