Great question—community gardens are hard on furniture, so I’d lean toward pieces that are heavy, simple, and easy to maintain. My first choice would be anchored concrete or stone benches. They’re almost impossible to move, have no loose parts, and can be finished with an anti-graffiti sealer. For a warmer look, use recycled plastic lumber slats on a powder-coated steel frame with tamper-resistant bolts; the plastic resists moisture and graffiti, and damaged slats can be replaced without replacing the whole bench.
If you need flexible seating, consider steel bollards with seat tops, fixed picnic tables, or concrete planter-seats. These give people places to sit and gather without creating loose chairs that can be thrown or stolen. Gabion benches filled with local stone are another sturdy option, though you need to cap edges carefully. Cast aluminum or cast iron benches are durable but expensive and can be targeted for scrap, so anchoring and security fasteners matter.
I’d also plan the space, not just the furniture: keep seating visible from nearby homes or paths, avoid dark corners, specify stainless or tamper-resistant fasteners, add drainage, and choose anti-graffiti coatings that suit your climate. Avoid lightweight movable chairs, thin slats that pry off, and decorative gaps where litter collects. A mix of concrete, recycled plastic, and anchored steel usually gives the best balance of durability, cost, and comfort. If your budget is tight, spend it on anchoring and coatings first—those make more difference than fancy designs.