Answer: Mexican Bird of Paradise has orange flowers; Desert Bird of Paradise has yellow. Whatever the flower color, the plants are the same and can be quite invasive because they spread by both roots and seeds. You can control their sizes by simply pruning them down to ground level (with a tree saw if necessary). This won't eliminate the plants, but will keep them on the small side if done annually. To completely rid your landscape of these shrubby plants, cut them down to ground level and paint full strength Round-Up on the fresh cuts. Round-Up will translocate to the roots and kill them off. Withholding water to the roots might help, too.
Best wishes with your landscape!
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