Looks like a tree sucker. What trees are in the vicinity?

There doesn't seem to be a similar-looking plant near where any of these sprout. Attached is a picture of the property. These things seem to pop up randomly (scattered) within 10 ft of the walls to the right, so that includes areas near the back where the shade is and near the white lily plants in the middle. The specific plant featured in my first photo was pulled near the right tower-ish plant.

I read this post further down (http://forums.gardenweb.com/forums/load/weeds/msg041954384899.html?3) and the plant I pulled seems similar in a few ways. There is a purple-flowering vine over my neighbor's fence (in the back shady area in the most recent picture). I'll get a pic of those vines and try to have them ID'd and see if the suckers match the description.

Thanks, floral_uk... it does appear to be a sucker based on the horizontal root. What threw me off was that it's so far out from anything that looks like it, and there was also a sizeable sucker in the crack between the wall of the house and the concrete.

Dug up some more today and these are definitely suckers... dug up a root at least 5 ft long running just underneath the turf. Upon closer inspection, these seem to be coming from a dead-looking tree on the other side of the fence in my neighbor's yard. I just noticed there's a bunch of bigger ones there haha... yeah. I'll send it to the other forum for ID since it doesn't appear to be a weed.

I guess that first one I posted came from a root that ran at least 20 ft from the fence across the front of the house...

Thanks for the help!