If you want to start a few seedlings, without fear that they will receive sufficient water and light to make them grow, consider this:
Toilet Tank Lid PlanterYou can see from the link that this is a really old idea, and other links suggest that bathrooms are not healthy places to grow edible plants. But this is just for temporary, right?
Since such tops can no longer be found, I suggest an alternative, use some easy to assemble styrofoam or foam-board pieces to hold a plastic drywall compound tray, (or something of similar size. It needs to fit the tank.) You'll need to choose where the water enters and leaves..
The rest of it depends on the configuration of your toilet refill valve. You could let the tray dip into the top level of the tank, or cycle the refill tube through it. Use your imagination.
Note: If you can find the right kind of material for the top, you could just make some large holes in it, and drop in some standard clay flower-pots.)
Make sure nothing interferes with the refill mechanism,!
Then you'll need to set up a grow light over the tank, (with a 24-hour timer). Keep the electricity safely separated from the water.
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Or you could just buy more mature seedlings from the co-op store when you get back from your trip.
If my bathroom size allowed such a luxury, I might consider it. But with the fact that two crops of tomatoes are the norm, here, I can get the seedlings when I get back. It would be nice to have a really fresh tomato sandwich! :o])
“Mature” Exactly! That’s why the FFA sells transplants! You’ll not only encourage and support some very upstanding and solid young citizens and their endeavors, you’ll get very healthy and beautiful tomato plants and whatever else it is they happen to cultivate! It’s a very feel-good experience.