As temperatures drop, your urban planter boxes need special care to survive the winter. The first step is to know your plants. Tender perennials and tropicals often need to be brought indoors. For hardy plants staying outside, begin by ceasing fertilizer in late summer to discourage new, frost-sensitive growth. Thoroughly water the soil before the ground freezes; hydrated roots withstand cold better than dry ones. Apply a thick layer of mulch, such as straw, bark chips, or shredded leaves, over the soil surface. This acts as an insulating blanket, protecting roots from freeze-thaw cycles.
Next, consider the container itself. In cold climates, terra cotta and ceramic pots can crack. Insulate them by wrapping the exterior with bubble wrap, burlap, or specialized horticultural fleece. Grouping pots together in a sheltered spot, like against a building wall, provides mutual protection from wind. For added defense, create a windbreak or use a cloche or cold frame. For very sensitive boxes, moving them to an unheated garage or shed can be ideal. Remember to check soil moisture periodically during winter warm spells and water sparingly if dry. With these steps, your urban garden will be ready to thrive again come spring.