Getting Sidebar background to go all the way to the footer

Hi All,
My issue is that when the main content in my blog extends beyond the base of my sidebar boxes (which is often) the sidebar background cuts off and is all white. I tried setting the height at 100%, as well as repeating an image, but they all cut off at the base of the boxes, instead of extending all the way down to the footer. You can view it here:

https://margaretfeinberg.com/new/?page_id=7

Thanks!