Your plant is not a cactus. Its a Euphorbia.

The weed is some sort of Acacia. The bipinnate foliage is the juvenille
form.

http://farrer.riv.csu.edu.au/ASGAP/acacia.html


"Bernhard Kuemel" wrote in message
...
Hi sbb!

We have an unknown plant growing with our cactus. Can you id it?

http://bksys.at/bernhard/img/x14/-gallery.html?sbb

Thanks, Bernhard, Elke