This almost sounds like a transmap rendering problem.  Leaves on plant material are usually composed of transparency maps to reduce mesh size and weight within a scene.  Maybe reducing your bucket size may remedy the issue.  However, you didn't provide enough information to determine the source of your crashes.

What are your render settings?
Is your scene heavy in displacement mapping?
How many lights are present? 
Are you rendering with raytracing on or off?
Post a screencap of your scene and settings for better visual assessment.  There are many factors which might be contributing to render failure.  Better to find out now then to repeat the same pattern next time and have your render crash again.

@ leezace: it is fine to recommend an upgrade but, without understanding the nature of the problem, how are you sure that it doesn't also occur with that version?

Let's determine what is going on first and correctly address it's resolution so it may be avoided next time.