Here’s what I love about plant identification; the description for the leaves of Wholeleaf Rosinweed is that they are mostly opposite, but sometimes alternate or in whorls of three, and the same description for Whorled Rosinweed is that they are mostly in whorls of three, but sometimes opposite or alternate. So what are you supposed to do, perform a statistical analysis of the arrangement of leaves along the stem to determine what they mostly are; opposite or whorled? And what about the name Wholeleaf? As far as I can tell, the leaves of both plants are whole.
Being ever hopeful, I look up the Latin names of both plants, knowing that the taxonomists would come to the rescue! They are both Silphium species, that genus that Aldo Leopold made famous. Whipping out my handy dandy Latin translator, I look up “integrifolium” and “trifoliatium”. Integrifolium means “entire leaf”, referring to the property of having leaves without teeth or lobes. Hmmm, sounds a lot like “Wholeleaf” to me. So, on to trifoliatum, which means trifoliate, which means three leaved, which could be either a compound leaf or … a whorled leaf!! So, no help from the taxonomists. Did they define the Latin name based on the common name, or was it vice versa!
So anyway, the plants do have a different “look” to them, although the flowers are quite similar. Wholeleaf is a shorter, neater looking plant with the leaves marching smartly up the stem. Whorled are larger, ganglier looking plants.