Why not use 36" inch boxes and center them? That's what I've done for wider windows. You'd have just 4.5" left on each side. Not even noticeable.

Hmmm...I guess I could. I was worried the box would look lost.

I wouldn't go with the smaller window boxes. In fact, if there are shutters, the boxes should extend beyond the windows.

But more importantly, does the landlord allow you to drill holes in the outside of the building to install the boxes?

Yes, I cleared it with the landlord. I'm not irresponsible~ There are no shutters.

I had the same problem when I was trying to buy window boxes for my MIL's house. I shopped all over the internet and locally. The larger size ones are expensive. I ended up having my husband make them - which of course doesn't help you.

Maybe you could go another route with decorating the areas below the windows. Mandevilla growing up trellises would be pretty and easy.

Thanks for the suggestions...my mom ended up with the Mandevilla~

I found two iron 36" window boxes on sale for $25 each and went for it...I put a dwarf Boxwood, white Geraniums and a trailing Licorice vine. I also found an old urn at my husband's shop and put a 2- balled topiary in it with white wave Petunias...mission complete...it looks better than it did. I hope he will be surprised. Thanks for all the input.

Too late to help you but Wal-Mart had 24" iron and coco fiber window boxes for $6 or $7 each. Maybe this will be a working solution for someone else.