Yes, applying a sealant is one of the best things you can do to protect your concrete urban planter boxes and significantly extend their lifespan. Unsealed concrete is porous, absorbing water which can lead to cracking from freeze-thaw cycles, efflorescence (white mineral deposits), and staining from soil and fertilizers. A quality sealer creates a protective barrier against these elements.
For planter boxes, use a penetrating, breathable sealer designed for concrete. These sealers soak into the pores without forming a surface film, allowing moisture vapor to escape while blocking liquid water. This prevents internal pressure buildup that can cause spalling. Avoid glossy film-forming sealants for the interior, as they can trap moisture.
Ensure the concrete is completely clean and dry before application. Apply the sealer according to the manufacturer's instructions, typically with a roller or sprayer, coating both the interior and exterior surfaces thoroughly. Reapply every 1-3 years, or as recommended, to maintain optimal protection. This simple maintenance step will keep your planters looking great and structurally sound for many growing seasons.