Building raised bed with used redwood fence boards

My neighbor is a fencing contractor. He normally takes to the dump his old fence boards and 4x4s. Can I stake up the redwood fence boards 2 or 3 thick to use them as boarders for the garden. Is there something I am not thinking about.

Also there is a company down the street from me that bundles these boards and resells them.

https://goodnews.eco/

Those would be absolutely perfect! Because redwood is naturally rot resistant, you'll get a long life out of them AND can be reasonably assured they were not treated with any preservatives (because they never needed to be.)

Free is my favorite price.  You can also pay yourself on the back for using something that would have otherwise ended up in the dump.  I used an old  wood twin bed  frame my niece was talking to the dump.  It wasn't redwood, and it lasted about 4 years.  I would do it. Good luck.

Martin - sounds good!  Most redwood won't be treated or stained  - and even if it was its probably so weathered that whatever was there is gone.

One thing you might consider:  putting together some 1/2" or 3/4" fence boards won't be as stiff as a 1.5" board.  So three of them sounds good ... plan to screw them together.  You might want/need to provide a 2x2 as a backer for the screws to sink into and to provide additional stiffening.