Introduction
It may seem strange to think of your refrigerator as an ally for your indoor plants, yet it offers two genuinely useful services: extending the shelf life of your seeds and breaking the dormancy of certain seeds with cold. On the other hand, two frequently repeated ideas, creating a microclimate for orchids or dechlorinating watering water, do not hold up to scrutiny. Here is what actually works, and why.
Storing Seeds for Longer
Cold slows the ageing of seeds, provided they are perfectly dry. Place them in an airtight container (a glass jar or a sealed plastic box), ideally with a silica gel sachet, then keep them in the refrigerator at around 2 to 5 °C. The enemy is moisture: a poorly dried seed or a non-airtight container lets in condensation, which encourages mould. Take the container out of the fridge and let it return to room temperature before opening it, so that airborne moisture does not condense on the cold seeds. Kept properly dry, most vegetable seeds retain good germination potential for several years (Penn State Extension).
Breaking Dormancy: Cold Stratification
Many temperate perennials, trees and shrubs only germinate after experiencing a period of winter cold. You can reproduce this in the refrigerator, a technique called cold stratification. The often-forgotten key: the cold must be paired with moisture. Mix the seeds into a slightly damp medium (sand, vermiculite or paper towel) inside a sealed bag, and place the whole thing in the refrigerator, between 1 and 5 °C, never freezing, as frost can damage the seeds. The duration varies by species, from a few weeks to three months. The medium should stay just moist, never soaking, or it will rot (Penn State Extension).
What the Refrigerator Does Not Do Well
A Microclimate for Orchids
You sometimes read that you should put certain plants in the fridge overnight to mimic the cool of night. In practice this is a bad idea: a refrigerator runs at around 4 °C, in complete darkness, which is far too cold and too dark for a houseplant, just as it is for fruits and vegetables that are sensitive to cold. Orchids such as Phalaenopsis do not need anything so extreme: a day/night difference of roughly 5 to 8 °C is enough to trigger flower spikes (American Orchid Society). To achieve it, move the plant closer to a cooler window in autumn or lower the room heating at night, rather than putting it in the refrigerator.
Dechlorinating Watering Water
The chlorine in tap water evaporates mainly when the water stands in the open air, at room temperature, in an open container. The refrigerator actually slows that evaporation, so it does not help to dechlorinate. Moreover, many supply networks use chloramine, which is far more stable and barely evaporates when water is left to stand. Finally, cold water straight from the fridge can stress roots: most plants prefer water at room temperature. So to reduce chlorine, leave the water uncovered on the worktop for a day, not in the fridge.
Conclusion
The refrigerator is a real help for your plants, but on two specific points: storing seeds well and dry, and breaking dormancy through cold stratification. For everything else, a cool room and room-temperature water will do far better than the fridge door. And to keep your herbs in good shape, look instead at the methods that actually work.