Plant identification?

Plant or weed identification time.

• What is this plant (or weed) growing in my back yard? It has multiple, thick stems with tiny thorns, green leaves that turn light green/reddish as the plant gets bigger, and a big root system with roots that are woody and slightly rubbery. It does not have any tendrils or flowers and left to grow, it begins to resemble a small tree. I have six of http://www.nickbritton.net/etc/weedthing2.JPG growing in my backyard. They have appeared each of the three summers I've lived in my home--I started with just three and three more have appeared in the same areas. So I have two distinct locations with three of these things. I have checked standard weed and plant identification sites and had no luck. No other posts on here appear to have similar items. I let one grow last year and it got about a foot high. It resembled a tree and had no flowers. I finally dug it up and it had a relatively big root system with light colored, woody and slightly rubbery roots. The plant/weed in that location came back but grows much more slowly than it did last year. They show up in the late spring/early summer (late May or June here). You can't simply yank them up. The leaves are either green or greenish-red, but they tended towards a mix of light green/red as they got bigger. The stem is light green with reddish, very fine thorns on it. As you can see from the pictures below, there are multiple stems and the leaves have teeth. I live in the Salt Lake City area which may help with identification. http://www.nickbritton.net/etc/weedthing2.JPG http://www.nickbritton.net/etc/weedthing1.JPG I did not plant anything in these locations and there's nothing unique about their locations: one patch is near a wooden fence but the other is in the middle of the yard.

• Answer:

  They look like my new growth raspberry bushes. I have a bunch of these in my garden, offshoots from a couple of raspberry bushes I planted a few years ago. Raspberries can resemble weeds because they grow from basal shoots. From Wikipedia: "Raspberries are very vigorous and can be locally invasive. They propagate using basal shoots (also known as suckers); extended underground shoots that develop roots and individual plants. They can sucker new canes some distance from the main plant. For this reason, raspberries spread well, and can take over gardens if left unchecked."