Spiny-stemmed is an adjective used to describe plants that have prickly stems. However, if you are looking for alternatives to this phrase, there are a few options available. One could use "thorny-stemmed" as a perfect synonym, since both words carry the same meaning and convey the idea of spines or thorns. Other possible alternatives include "barbed-stemmed" and "bristly-stemmed," both of which give a visual image of a plant that is rough to the touch. If you are looking for a more poetic way to describe these types of plants, you could use "jagged-stemmed" or "razor-stemmed" to create a more vivid and descriptive picture.