this happened after Tuvok trounced the Vidiians...
Very nicely. We should have vine-ripened Talaxian tomatoes in a couple of months, unless this planet has the equivalent of tomato bugs. Oh, they're awful.
then two scenes later Voyager is in orbit and...
[Outside the shelter]
(The tomatoes are suddenly nearly full grown. Janeway and Chakotay are back in uniform and not looking too happy. All the equipment is packed up.)
(The primate turns up.)
JANEWAY: There you are. At least I get to say good bye. Feel free to use the house. Janeway to Voyager. Two to beam up.
point is that she hadn't been growing the Tomatoes for as long as it took the tomatoes to grow since Tuvok got as far away from the planet as he could before she planted them and then had to come all the way back over their own tracks. (Janeway makes too many enemies. She would have had to have charted an alternate, certainly longer, route to circumnavigate all the federations new enemies she had made. Kudos to Captain Tuvok.)
Several months times 2.
They could have been on that planet for half a hear or longer.