To coax the best flavor and longer life out of your tomatoes you’ve got to pay a little bit of attention to their “moods,” if you will. Knowing what they like makes all the difference in keeping them fresh longer and ready for when you are.
Unripe? Think Upside down. Yes, unripened tomatoes should be kept stem side down, in a paper bag or single layer in a cardboard box in a cool area until they turn red in color.
Ripe? Think Right side-up. Tomatoes are best kept at room temperature, on the counter away from direct sunlight, not touching one another, stem side up.
Don’t store tomatoes in plastic bags. The ethylene trapped inside will speed up their ripening – perhaps taking them too quickly to rottening.
Well ripened tomatoes can be put in the fridge to slow further ripening, but do let them come to room temperature before eating them.
Co-Author of Garden Candy Basics