Subpage display depth

Hello,

I am trying to work out subpage display depth. At the moment, by subpages are displaying in the sidebar so:

Apple
– Apple 1
– more apples 1
– Apple 2
– More apples 2

Banana
– banana 1
– more banana 2

Basically, I have 5 main pages, each with lots of pages and subpages. As my site will have potentially have more pages, the sidebar will be about 3 miles long down the page.

I have been trying to get the sidebar to show just the main pages on the static front page, then 1 child page for each of that on a subpage using the depth and child_of fucntions, but with no decent results. Can anyone recommend a decent solution? Ideally, I only want the subpage depth to go down one step (if that makes sense?)