Tosefta על מעשרות 1:5

The "granary" for tithes [of produce] (i.e., the point at which produce must be tithed) rendering one liable on account of the laws of tevel (i.e., the prohibited consumption of or benefit from untithed produce), is once their work is completed -- [meaning] the work of being brought in [from the field]. (See Bava Metzia 88b:6).)

They separate Terumah from gourds and pumpkins, even though the watermelons and cucumbers did not yet have their fuzz removed [in hot water, following MSS Erfurt (see Maasr. 1:5)]. Even though he did not remove the fuzz from the cucumbers that he intends to remove from the kettle, he is not liable [for tithes] until he [does in fact] remove them from the kettle.