If a squash still on a vine but not attached to the ground is declared tamei, it may not be eaten or burned, but may it be opened and the seeds planted? Would the ground not make the seeds tahor and plants grown from those vines tahor?
RUS BAS SARA, BOCA RATON, FL. USA
Food that is Tamei loses its Tum'ah when planted from the moment it takes root (Rambam, Hilchos Tum'as Ochlin 2:19, based on Toras Kohanim).
Food that is not Terumah or Kodesh may be eaten even if it is Tamei (and need not be burned).
If the squash you are discussing was Terumah Tamei, it may not be planted. Even if it is planted, the it (and whatever grows from it) will remain Tamei. This is a Rabbinic institution, lest Kohanim store their Terumah Temei'ah until the growing season and accidentally eat from it in the interim.
Best wishes,
Mordecai Kornfeld
Kollel Iyun Hadaf