"Beautiful Cashmere" in the earliest (1901) printed version that anyone has mentioned in Mudcat.
I, for no good reason, have always favoured the Himalayan balsam option, although I have not seen any nineteenth century source that backs that up.
What I did notice recently in a History of Hawick, was the fact that Himalayan balsam (along with giant hogweed) was introduced in the nineteenth century to the river Teviot by the processing of cashmere wool. The wool contained the seeds of those two plants which were washed out and subsequently naturalised themselves along the river. Given that the plants were new to the area, what would the locals have called them other than the beautiful cashmere plant and the other one?