I’m pretty sure that plant is called Rosa Rugosa, a type of rose with large seed pods that can be used to make rose hip tea.
Rosa rugosa (rugosa rose, beach rose, Japanese rose, or Ramanas rose) is a species of rose native to eastern Asia, in northeastern China, Japan, Korea and southeastern Siberia, where it grows on the coast, often on sand dunes.[1] It should not be confused with Rosa multiflora, which is also known as "Japanese rose". The Latin word "rugosa" means "wrinkled."
I just happened to see some of this here in Maryland the other day. Distinctive flower type.
Heres the wiki link - https://en.m.wikipedia.org/wiki/Rosa_rugosa
So id say you can esaily feed the flowers/petals, you can doublecheck on the tortoise table site. Not sure how much nutritional value in the flowers.
We have these in Maryland?? Where abouts?