Your appreciation for wood's natural aesthetic is well-founded, and cedar is an excellent choice for urban planter boxes. The direct answer is that cedar is naturally resistant to rot and decay, but it is not entirely immortal. Over a long period, it will eventually show signs of aging, though this process is slow.
Cedar wood contains natural oils and tannins that act as preservatives, protecting it from moisture, insect damage, and fungal decay that cause rot. This inherent resistance is why cedar is a premium material for outdoor projects without needing chemical treatments.
Several factors influence how long your cedar planter will last:
1. Climate and Moisture: Constant exposure to damp soil and rain will accelerate wear. Proper drainage is crucial to prevent water from pooling at the bottom.
2. Soil Contact: The part of the wood in direct contact with soil is most vulnerable. Using a landscape fabric liner can create a protective barrier.
3. Maintenance: Applying a sealant or wood preservative every year or two can significantly extend the life of your planter by repelling water.
While untreated cedar planters can last 5 to 10 years or more, those that are well-maintained can serve your urban garden beautifully for 15 to 20 years. The silver lining is that even as cedar ages, it gracefully weathers to a charming silvery-grey patina, maintaining its structural integrity and rustic appeal long after. So, you can confidently choose cedar for its beautiful look and proven durability.