Yes, it’s possible.
Remember that even on Palm Sunday, the branches we should be using are from palms and olive trees. In places where it’s not possible to obtain either, other plants are used on Palm Sunday (I’m think specifically of the Russian custom of using pussywillow branches).
For Ash Wednesday, the Church recommends using ashes from the palms and olive branches of the previous year, but does not require them.
So again, yes, it’s possible.