Whether you need a liner in your urban planter box isn't a simple yes or no answer. It depends on your planter's material and your gardening goals. For wooden planters, a liner is highly recommended. It acts as a barrier against constant moisture, preventing rot and extending the planter's life significantly. Without one, soil and water directly contact the wood, leading to decay within just a few seasons. For metal planters, a liner is crucial to prevent soil from reacting with the metal, which can alter soil chemistry and harm plant roots. Concrete and stone planters are more durable but can leach minerals into the soil over time; a liner helps prevent this.
The primary benefits of using a liner are protecting the planter structure and improving moisture control. However, proper drainage is non-negotiable. Always ensure your liner has adequate holes at the bottom, or use a permeable landscape fabric, to allow excess water to escape. Stagnant water is a leading cause of root rot. For a simple solution, many gardeners use heavy-duty plastic with drainage holes poked in the bottom, or specialized pond liner material. Ultimately, adding a liner is a small step that safeguards your investment and creates a healthier environment for your plants to thrive in the city.