Here in Albuquerque, NM, we have the annual fall of Tingley snow in the spring. These are the seeds of Ulmus pumila (siberian elm) that were introduced by the mayor of Albuquerque, Clyde Tingley. Tingley purchused 2,000 of them for $20 some time in the late twenties or early thirties, put them out by the bank of the Rio Grande, and gave them away to whoever would plant them. Now, although there are some stately examples of the tree here and there, its more or less a weed tree. And yes, just like Ed Merc with his Ulmus parvifolia, the seeds can cover the yard, and it is snow like on a windy sping day that they fall or just swril around. On the upside, they give me free stock to play around with from seedlings coming up or root suckers. Sorry I,m no help with your question, but maybe one day I'll have the experience to answer it....?