My new starter trays arrived. Lee Valley calls them deep root cells. They aren't as deep as the ones I'd gotten from them last time. I've been filling them with potting soil in preparation for my cuttings for next spring. I will save a few for starting seeds in February. The white powdery stuff is diatomaceous earth. I have seen slugs and want to make sure they don't survive if I bring some in with my cuttings. What you see is two of those trays. I bought fifteen of them to go with the ones I already have.