According to the New York Flora Atlas, there are 36 species of hawthorn (Crataegus spp.) that have been reported outside of cultivation in New York State (including two with two subspecies reported). Plus, 12 different hawthorn hybrids have been reported in New York, for a total of 50 separate hawthorn taxa.
Of these 50 taxa, all except Crataegus monogyna (English hawthorn or common hawthorn) are native to New York. But maybe not surprisingly, English hawthorn seems to be the most common hawthorn species at the Federal Farm. English hawthorn is not on a New York invasive species list, but it is considered to be invasive in California.
There are also several commonly-cultivated hawthorns in New York that are Southern US natives. These include Green hawthorn (Crataegus viridis) and Washington hawthorn (Crataegus phaenopyrum). Some sources do show Washington hawthorn as a New York State native, but it’s unlikely that it would be native this far north. These two southern natives have not been identified at the conservation area and it probably wouldn’t be appropriate to plant them there.
Crataegus monogyna (English hawthorn) at the Skaneateles Conservation area.