Ostrya knowltonii Sarg.

Ostrya knowltonii Sarg.. Ostrya knowltonii is a species of tree known by the common names Knowlton's hophornbeam, western hophornbeam, woolly hophornbeam, and wolf hophornbeam. It is also one of many trees called ironwood. It is native to Utah, Arizona, New Mexico, and Texas in the United States, but its distribution is localized and sporadic.