The Mystery of Mulberry

We have recorded high levels of mulberry pollen at our NAB station in SW Ontario, Canada from 2010 to 2021. Mulberry trees are rare in SW Ontario; could "our" Morus pollen originate elsewhere? Possible sources located to our West & SW where NAB stations regularly report high levels of Morus pollen include Chicago, Omaha, Kansas City, Madison WI & St. Louis. We tracked pollen-containing air currents over 72-hour periods from those locations using NOAA HYSPLIT forward projections to see if some of "their" airborne pollen might be carried our way. Morus pollen from all the above areas was carried to our location according to their reporting and HYSPLIT trajectories. Pollen from the Chicago area was the main contributor (9 of the 12 years). We also saw examples when conditions were ripe for Morus to be deposited here but was not. Our results strongly suggest that mulberry pollen we report is a result of long-distance transport, but sometimes it did not result in local Morus pollen deposition.