It fits with the ends in -en trend in boys' names without being common like Jackson or Aidan/en, but do you think a boy would be bullied for having a name that's more popular for girls (it ranked at #372 for girls in 2015, so not exactly common for them either) or is it still usable?
I probably wouldn't use it, but I totally would love to meet little boys named Aspen. It just has a masculine vibe to me and feels more refreshing and unexpected.