I paint mine with exterior grade latex house paint. They last about five
years. A yearly paint job would probably make them last forever.

--beeky

Phisherman wrote:

I've been given a few wooden (pine) flats for starting seeds and
wondering the best way to finish them to help prevent them from
rotting? Paint? wax? paraffin? Linseed oil? Any finishes to avoid?
I'll be using them for starting seeds next month for next year's
vegetable & herb gardens. Thanks.