A 069 No.
Quote Originally Posted by Vow of Poverty
Special: To fulfill your vow, you must not own or use any material possessions, with the following exceptions
Armor (of any sort) is not on the list of Vow of Poverty exceptions, so a Druid even temporarily owning the result of the Ironwood spell would incur the standard penalty:
Quote Originally Posted by Vow of Poverty
If you break your vow, you immediately and irrevocably lose the benefit of this feat.