This question already has an answer here:
I read this series about 15 years ago give or take. It was in the young adult section of the library and I think there were at least 3 books or so. The main identifying features were two alien races.
One race was cone shaped and if I recall correctly very nature oriented. I believe they used nature-oriented technology, and could grow machines. There was something about covering huge areas of water with these plants. It was one of the things that could cause friction with the other factions since the plants choked the lakes or something.
Of the other I recall that they were physically strong and had a lot of natural weapons. They wanted to be civilized and usually were, but they built up a hormone of some sort that required them to release by going into aggressive rages at regular intervals. They may have had special events, rituals or locations dedicated to venting their rage hormones. Being stranded with one was extremely dangerous if they could not vent.
The central overarching story was about how these three races (the two above and humans) would try to live together and learn from one another but their differences put them on edge constantly and there was always tension.
I remember the books having black bars on the top and bottom like a 4:3 tv showing a 16:9 film, and I think the author sounded American. I've asked the same question on Goodreads to no avail, and google has failed to yield a single clue.
Does anyone know what series this is?