Ipe has been the benchmark for outdoor wood durability for two decades. Black locust is the domestic alternative — cheaper, more sustainable, and nearly as durable.
Key Specs at a Glance
Ipe: 3,510 lbf Janka, Durability Class I, 40–75+ years outdoors, $15–$25/bf. Black locust: 1,700 lbf Janka, Durability Class I, 30–60 years outdoors, $4–$8/bf. Both carry the highest natural rot resistance rating. The durability gap is narrower than most people expect. The price gap is enormous.
Rot Resistance, Workability, and Value
Ipe's durability: extreme density (specific gravity ~0.95), high silica and tannin content. Black locust's: flavonoid compounds including robinin that are toxic to wood-decay fungi. Both have documented 50+ year outdoor service lives. Ipe at 3,510 lbf is nearly twice as hard as black locust (1,700 lbf), dulls blades rapidly, and checks without UV oil maintenance. Black locust requires carbide blades and pre-drilling but is much more manageable for DIY. For raised beds, trellises, and cold frames, black locust is the practical choice. A standard 4×8 raised bed (35 board feet): ipe costs $525–$875; black locust $140–$280. The durability difference does not justify a 3× price premium for garden use. See our ipe sourcing guide and cedar guide.
Sustainability
Ipe is a tropical hardwood from Brazil with difficult-to-verify supply chains even with FSC certification. Black locust is domestic, fast-growing (20–30 year rotation vs. 50–100 for tropical species), nitrogen-fixing, and sustainably cultivated. For sustainability-conscious gardeners, black locust is the clear winner.
Frequently Asked Questions
- Is black locust really as rot-resistant as ipe?
- Both are Durability Class I, but ipe has a slight absolute edge — it is denser and its extractives more concentrated. In practice, both far outlast any practical garden structure lifespan.
- Can I use black locust for decking the way I would use ipe?
- Yes. Black locust decking is used in Europe and gaining traction in North America — pre-drill all fasteners, and it weathers to silver-gray if left unoiled, but checks less aggressively than ipe without maintenance.
- Where can I find black locust lumber?
- Regional sawmills in Appalachia, the Mid-Atlantic, and Midwest are primary sources. Online hardwood dealers increasingly carry it. Expect lead times for specific dimensions.
- Does black locust need the same annual oiling as ipe?
- Less so — it is less prone to checking than ipe and tolerates being left unfinished better. Annual oiling helps appearance but is less critical for structural integrity.
- Which is better for a garden trellis or arbor?
- Black locust — ipe is too heavy, expensive, and hard to work with for vertical garden structures. Black locust provides more than adequate rot resistance at a fraction of the cost.