To keep your homegrown tomatoes fresh longer naturally, the most important thing is temperature control and placement. Never store them in the refrigerator, as the cold breaks down their cell walls and ruins the flavor and texture. Instead, keep them at room temperature on the counter, ideally stored stem-side down. Storing them upside down helps prevent air from entering and moisture from escaping through the stem scar. Also, keep them away from direct sunlight and other ethylene-producing fruits like bananas, which can cause them to ripen and spoil too quickly.