The subjects you can take along with your BSc Physics is entirely dependent on the college/university you are studying at. If they offers the course, then you can take. But in general for BSc Physics the combination don't occur with Botany. The most efficient elective for a career in Physics is that you must keep Mathematics compulsorily as an elective because many Universities needs Mathematics mandatorily in your BSc. Apart from this you can take Electronics, Chemistry, Statistics, Computer science as electives which can be highly beneficial for your career ahead.

For more information regarding Physics you can consider the link below:

https://www.careers360.com/courses/physics-course

I hope this helps. Wish you a great day!