Urban planter boxes often benefit from having a liner to protect them from moisture damage, though the necessity depends on several factors. The primary purpose of a liner is to create a barrier between damp soil and the planter material, preventing rot in wooden planters and corrosion in metal ones. Without proper protection, constant moisture exposure can significantly reduce your planter's lifespan.
However, drainage remains equally crucial. Any liner you use must include drainage holes or allow water to escape somehow. Standing water can lead to root rot and create breeding grounds for mosquitoes. For wooden planters, a plastic liner with drainage holes offers excellent protection. For metal planters, a permeable landscape fabric can prevent soil contact while allowing moisture to evaporate.
Consider your local climate when deciding - wetter climates make liners more valuable, while drier regions might allow more flexibility. The planter's construction material also matters; naturally rot-resistant woods like cedar may need less protection than pine planters. Ultimately, combining a thoughtful liner system with proper drainage creates the ideal environment for both your plants and your planter box to thrive in urban settings.