Thanks for the comments guys!
The Cacti are Scene-A-Rama from Woodland Scenics, SP4124 - Desert Plants.
http://scenearama.woodlandscenics.com/show/Item/SP4124/page/1I found them at a local hobby store when I was grabbing some plasticard. The kit is pretty basic but has all the stuff you would need: Small and large cacti, grasses, scrub brush, desert flowers...it even came with glue (which I didn't use). The pieces are made of a softer plastic so the larger cacti were a bit warped but they were easy to repaint and held their paint once primed.
Plus with a name like Scene-A-Rama, I
had to try them