Is there anything I can use to slow wood rot for a vegtable garden. Something like pressure treated but non-toxic.
Are there paints that dry to form a plastic?
Try naturally decay resistant woods - western redcedar, Redwood in your area. Cypress is also widely available. Paints close to ground level are more likely to peal from the moisture.
Waterproof coatings usually need to be applied year after year.
I've started seeing the big box stores like HD carry PVC lumber. Basically, wood sized and shapped boards made from PVC. Lightweight, rot resistant and works like wood. You could also use some the composite deck materials made from plastics, like Trex.