Super Sprouter? 10 in x 20 in trays are the perfect solution for propagating your clones and seedlings with rock wool, seedling mix or starter plugs. The Super Sprouter? trays are available without holes to catch excess water and help to keep starts or plants moist and also with holes, to drain off excess water from the base of the cutting or seed. Raised channels are incorporated in the base of the trays to help air circulate under your pot or insert tray.