ANY organic oil will support mold growth if you live in a climate where that's an issue. Mildewcides work for a few months but not long enough to stop the mold over the course of a year. Ipe' is one of the most rot resistant woods available. That's what I chose for my deck. I finished it with Ipe' Oil. It looked gorgeous until the following spring when it was covered with a grimy mix of what looked like dirt and black mold. Rinse, repeat, for about 5 years trying various oil products. None survived a year w/o mold growing. And removing the grime and mold is not an easy task. TSP, bleach, deck cleaner, I've tried quite a few products. None work very well. Deck and fence cleaner followed by a serious power washing has worked the best. Twice a year, requiring more than 8 hours each time. I hate it.

On the other hand, this is the black locust bench that sits on my deck, before I changed it to Ipe'. It's finished with Epifanes. The finish lasted two years before it started to split and water got under it at those splits and caused it to start lifting. Sand, spot finish then finish the whole thing again. A year later more trouble. After the third finish repair, I decide a cover was the best option. I think it's been about 5 years and two covers later now, and the bench looks as good as the day I first covered it.



No finish will survive outdoors, exposed to the weather, w/o constant maintenance. But it will survive if you cover it when not being used and keep the feet off the ground.

Your other option is torrified wood and no finish. It'll still need cleaning, but it probably won't support mold growth.

John