snow balls

I'm actually not sure what these are - I hope someone more attuned to North American horticulture will enlighten me... If they were in England, I'd say that they looked like plane tree balls, but I don't think they are - too spiky, and looking like a rambutan.

There was a lot of snow today - around 13". That, admittedly, will not sound a lot to sufferers in DC or Maryland, but it's a good deal for Highland Park to cope with, and our trees are bending in an ominous fashion. It's hard taking adequate photographs that don't look like every other photograph - submerged cars, people on cross-country skis in the streets, chilly ducks floating down the Raritan with snow on their backs, neighbors' snowpeople, etc, especially in the dull grey light - and yet, there's something compulsive about documenting The Great Storm of February 10th 2010, so I've ended up with all of these...