what is safe to waterproof red cedar benches

[Fallon]

Hello all,
I have never joined a forum before so feel free to provide any feedback necessary. My question is Re: red cedar benches that I am preparing for my small heated greenhouse. I recently replaced my original ones that lasted approx. 15 yrs. and were not water proofed. I am now considering a sealer but am concerned over the safety for my orchids sitting directly on the bench. I also wondered if the sealer could eventually peel with weekly water. The former benches remained clear of algae etc but merely dry rotted. Any suggestions or shared experience would be appreciated.
Fallon