Jiffy-7 Seed Starting Pellets 25 Pack When soaked in water, these Jiffy pellets expand to significantly to 1.25" dia x 1.25" tall when fully expanded, creating an all-in-one seed starting system. Jiffy 7 peat pellets are rapidly becoming the #1 choice of gardeners everywhere. Jiffy pellets are the all natural approach to plant propagation. They come pre-formed and ready for planting, simply expand with water. Jiffy peat pellets are the ideal choice for indoors seed starting. The soft walled pellets allow plant roots to naturally air prune as they emerge through the pellet. Jiffy 7 peat pellets are a consistent seed starting medium that is optimized for propagation and root development.