Yes, unheated greenhouses can work for growing plants, but it depends on the types of plants you want to grow and the time of year. Here are some points to consider:
In colder months, an unheated greenhouse can act as a shelter for plants that would otherwise struggle in the harsh outdoor conditions. This can include cold-hardy vegetables like kale and spinach, as well as many types of herbs.
In the spring and fall, an unheated greenhouse can provide a warm environment for starting seedlings. This is particularly useful if you live in an area with a short growing season, as it allows you to extend the season and get a jumpstart on your garden.
In the summer, an unheated greenhouse can be too hot for many plants, making it less useful for growing. However, it can still be useful for drying herbs and preserving food.
When it comes to preserving food, an unheated greenhouse can act as a sort of root cellar, providing a cool, dry environment for storing fruits, vegetables, and other crops. This can be particularly useful if you have a bumper crop and need to store your harvest for later use.
Finally, an unheated greenhouse can also be useful for drying clothing, particularly in humid environments. Simply hang your laundry inside and the dry, warm air will quickly do its job.
Overall, while an unheated greenhouse may not be as versatile as a heated one, it can still be a useful tool for gardeners looking to extend their growing season or preserve their harvest.