Good Evening,
As has been pointed out, the 18-55 is a pretty good choice, since you are going to be stopping down to around f8 to increase the depth of view within the image. You can also do a lot of experimentation with focal lengths. You can stitch shots together from 50mm, then again 30mm and then 18mm and compare them against each other. I think you will find that the wider focal lengths, bring in more "scene" in the foreground. Also, I think that you will be surprised at the level of detail in the narrower focal lengths as compared to the wider focal lengths. Stitched panoramas can be shot at any focal length. Its just the longer the focal length the more shots you need to stitch together for a view - but the detail within the image will be increased when compared to a wider lens.
I only point this out, since some experience will help you finally decide on which wide angle lens to possibly purchase. There are a number of choices - Primes of 17mm, 15mm, 14mm along with Zooms of 8-16, 10-20, 10-24, 12-24. One aspect of wide angle lenses that your current 18-55 will not really exhibit is the amount of distortion at the wider focal lengths - 8, 10, 12mm etc. especially along the side and corners. This is just a byproduct of pulling in a lot of scene around the edges, so that it can be recorded on the sensor. Another side effect is that the center is pushed back a bit in order to make room for the additional view coming in from the sides.
Wide Angle lenses pull in more scene and "stuff" it on the fixed size sensor, i.e., as the focal length gets smaller, there is more view that needs to be laid on to the sensor. With stitching, you are actually adding pixels for each short that you are using to stitch into a panorama. Also, shooting in landscape orientation, produces some very loooong skinny images, while shooting in portrait mode (camera tipped up on its side) provides some increased vertical height.
If you don't have any stitching software, Microsoft ICE is very good and its free - just a download...