How to unwarp Pine sleeper?

[J-P]

I have treated pine garden bed (around 5-7 yrs old) running alone the perimeter of the house. They have been capped with 75mm sleeper on top and some of them have warped over time. I see the that the capping has been secured by nails. Would I be able to straighten the capping by screwing batten screws? The timber has warped atleast by 5-10 cm in certain places.

[Dave-1]

Afternoon @J-P and @Noyade 

I have done the reverse of all things.. I had stored some long rails of timber up the side of the house between two far apart points. Over time it did bannana a bit tho not as much as that one It was hard wood, this is pine so maybe it could be flipped upside down with a bit of weight in the middle and wait a year or so... O:)

Dave