When frost threatens your urban garden, your planter boxes need special attention. Unlike in-ground plants, container plants are more vulnerable to freezing temperatures because their roots are exposed on all sides. Here are effective strategies to shield your greenery.
First, monitor weather forecasts regularly. When temperatures are predicted to drop near or below freezing, it's time to act. Move your planter boxes to a sheltered location if possible – against a south-facing wall, under an overhang, or into a garage or shed overnight. The thermal mass of buildings can provide several degrees of protection.
For planters that are too heavy to move, covering them is your best defense. Use frost cloths, old bedsheets, burlap, or even cardboard boxes. Avoid plastic sheeting as it can trap moisture and freeze against plant tissues. Drape the material over your plants before sunset to capture ground heat, ensuring it extends to the soil line. Secure the covering with rocks or clips to prevent wind displacement.
Add insulation around your containers. Wrap planter boxes with bubble wrap, burlap, or blankets to protect the roots. You can also group containers together to create a microclimate. Mulch the soil surface with straw, leaves, or wood chips to provide an extra layer of root protection.
Water your plants moderately before a frost – damp soil retains heat better than dry soil. However, avoid wetting the foliage as this can increase frost damage. For tender plants, consider using Christmas lights (not LEDs) under the coverings to generate gentle warmth.
Remove coverings once temperatures rise above freezing the next morning to allow plants to breathe and receive sunlight. With these simple precautions, your urban planter boxes can survive frosty nights and continue thriving.