Full slug for page including all parent pages and sub-pages

Assuming my page structure is:
Vegetables
– Tomato
– – Green
– – Red

The corresponding slugs are:
Vegetables – website.com/vegetables
– Tomato – websites.com/vegetables/tomato
– – Green – website.com/vegetables/green
– – Red – website.com/vegetables/red

Obviously this is wrong! I want the Green Tomatos to have slug :-
website.com/vegetables/tomato/green

How do i achieve this?

Note:
1. My permalink structure is: /%author%/%year%/%postname%/.

2. I have lot of pages, sub-pages and sub-pages. So making changes page-by-page is a pain.

3. Manually changing to /vegetables/tomato/green gets automatically changed to vegetables/tomatogreen! So thats not happening…

PS: I thought this was common sense! Duhh WordPress.. Why???!!!