In The Legend of Zelda: Skyward Sword for the Wii, you can upgrade the seed satchels in the game at the Scrap Shop by collecting various items throughout the world.
Here are the seed satchel upgrades, and what you need to collect to upgrade them.
Medium Seed Satchel – Upgraded From: Small Seed Satchel, Cost: 50 Rupees, Ingredients: 4 Amber Relics, 3 Monster Claws, 3 Ornament Skulls
Large Seed Satchel – Upgraded From: Medium Seed Satchel, Cost: 100 Rupees, Ingredients: 5 Amber Relics, 1 Blue Bird Feather, 1 Golden Skull, 3 Monster Claws
Check out my full upgrade guide if you’re looking for the other upgrades for equipment, potions, and wallets.