Spiny annual, annual and perennial sow-thistle are often confused with one another. Perennial sow-thistle can be differentiated from sow-thistle as it will be the first to emerge in the spring and will have an extensive underground root system. The leaves of perennial sow thistle are also not as deeply lobed as annual sow-thistle. Spiny annual sow-thistle can be differentiated from annual sow-thistle by its dark green leaves with purplish margins. The leaves of spiny annual sow-thistle also look and feel extremely waxy. Spiny annual sow-thistle is also more "spiny" or "prickly" to the touch versus annual sow-thistle. Lastly, spiny annual sow-thistle has leaves which have rounded basal lobes that clasp around the stem.