What's your question? Ask

Not enough water or not enough sunlight are the most common reasons for brugmansia leaf loss.

I am far from knowledgeable about Brugs so sent this question to a friend of mine who is a real guru. Here is her answer:

Susan, I would say she is NOT fertilizing often enough. I fertilize twice a week, and use a mixture of any good water soluble fertilizer and add Epsom salt and tomato fertilizer. Since they are in the tomato family, this really helps get more blooms. Also, they should NEVER dry out, and since hers are all in containers, she will have to water a lot.

They do sound under-watered. The water may not be getting to the bottom of the container. At least once a week, flood the container to the point of overflowing. This should ensure that the water reaches the bottom of the container.

This article will help: https://www.gardeningknowhow.com/ornamental/trees/brugmansia/prune-brugmansia-trees.htm

If you just want to kill the roots, when you cut the tree/bush down, immediately paint the cut stump wound with full strength Round-up. The root system will "suck" the Round-up into its system and will die. You may have to follow up with 1 - 2 fresh cuts to completely kill the whole roots system, but it works pretty well.

Here is an article that you may find helpful: https://www.gardeningknowhow.com/ornamental/trees/brugmansia/getting-your-brugmansia-to-bloom-and-produce-blossoms.htm