Jiffy Tree Seed Starting Peat Pellets. Put a seed in the pellet and add water - that's it! After the tree seed grows a 5-8 inches, transplant the entire pellet into a container or outdoors. Peat is perfect for root development of new seedlings. Peat has low PH, no pathogens, no insects or pests and is free from weed seeds. Size: 50 mm