How to make polystyrene seedling trays last longer

While thinking about how to prolong the lifespan of polystyrene seedling trays that are exposed to harsh sunlight, Bill Kerr began to wonder if a coat of paint might offer a solution.

- Bill Kerr

Polystyrene seedling trays start to degrade when exposed to the sun. I observed how they became pitted and rougher with age, with the seedlings’ roots starting to penetrate the cavity walls. This made removing the seedlings more difficult and increased the risk of damaging the root tips.

I tried painting the trays. Gloss oil paint, which would seem to be more desirable, did not work, because its chemical make-up meant it dissolved the polystyrene.

We are therefore left with PVA paint, which will not damage the polystyrene. PVA roof paint is made to withstand harsh sunlight and would likely be one’s first choice.