If you live in a region with harsh winters, this is a valid and common concern. The short answer is: they can, but it's not a foregone conclusion. The primary enemy of your planter boxes in cold climates is the freeze-thaw cycle. When water saturates the soil and the planter's material, it freezes and expands. This expansion puts immense pressure on the walls of the planter. When a thaw occurs, the ice melts and contracts. This repeated expansion and contraction is what causes cracking and spalling, especially in non-porous materials like ceramic, terra cotta, and concrete.
Your first line of defense is choosing the right material from the start. For cold climates, the most durable options are frost-resistant or frost-proof planters. These are typically made from fiberglass, metal (like corten steel), high-density polyethylene (plastic), or thick, treated wood. These materials are either flexible enough to handle expansion or are designed to be non-absorbent. It is best to avoid untreated terra cotta and thin, low-quality ceramics, as they are highly susceptible to moisture absorption and subsequent damage.
Proper preparation is key. Before the deep freeze sets in, ensure your planters have excellent drainage. Clear any blockages in the drainage holes. For an extra layer of protection, you can empty the planters of soil entirely for the winter. If you choose to leave the soil in, consider wrapping the planter in horticultural fleece or burlap to provide insulation, which slows down the rate of freezing. Moving smaller, vulnerable planters to a sheltered location like a garage or shed can also save them from the worst of the weather. By understanding the risks and taking these proactive steps, you can significantly increase the chances of your urban garden planters surviving the winter intact.