Flame issue with plants

[vamike]

For my deck/pool plan I created fire columns with flames using this approach:  https://www.chiefarchitect.com/support/article/KB-01830/creating-a-fire-or-flame.html.  I used a standard "closed box" shape vs. a polyline solid since I only have HDPro.

 

However, in my walkthrough, when any part of a plant is directly behind a flame, the plant renders as if it is in front of the flame?  Below is the video and you can see this problem at:  

• 1:35... various plants obscure the parts of the flame
• 2:37... the tree leaves obscure most of the flame, and
• at 2:50 exactly... the entire flame is obscured by the dense crepe myrtle

 

Is this a walkthrough render bug in HDPro or is it an expected behavior and I need to change something?  I appreciate any help on why this is happening.

 

Thanks,

Mike