That's an excellent question many eco-conscious gardeners are asking! The short answer is: in terms of structural strength and longevity for typical garden use, high-quality recycled plastic benches are not only comparable to wood but often surpass it in key areas. Let's break down why.
While a solid hardwood like oak has immense inherent strength, wood used for outdoor benches faces relentless enemies: moisture, insects, fungi, and UV rays. This is where plastic lumber, made from dense recycled HDPE plastic, shines. It doesn't rot, warp, or splinter. You'll never need to treat it for termites or mold. Its strength is consistent and unaffected by wet weather.
For everyday loading—people sitting, leaning, and gathering—a well-constructed recycled plastic bench is more than strong enough. It won't develop weak spots over time like rotting wood. The material is also flexible, allowing it to bear weight without becoming brittle. However, for extreme point-loading (like jumping from a great height), a thick, solid hardwood piece might have a theoretical advantage, but that's not a typical garden bench scenario.
The real strength of recycled plastic is in its endurance. A wooden bench, even pressure-treated, may last 10-15 years with significant maintenance. A recycled plastic bench easily lasts 20+ years with virtually no upkeep—no sealing, no staining, just an occasional wash. Its strength doesn't degrade season after season.
So, if you define "strength" as the ability to remain structurally sound, stable, and reliable for decades with minimal care, then yes, recycled plastic benches are a remarkably strong and intelligent alternative to wood for your garden.