If you swing your sword at a dandellion, a seed will fly into the air. As it descends, approach the seed and press the A button to summon a Korok. This will give you a Korok Seed!
You have the option of creating multiple seeds if you do not examine the seed in time. Fortunately, if you do not examine the seed in time, it will fall to the ground and disappear.
Examine the dandelion seed!
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If you obtain the Korok Seed, you can bring it to Hestu for various upgrades, including more inventory slots!
Where Can I find Dandelions in TOTK
While dandelions aren’t the only way to get Korok Seeds in Tears of the Kingdom, you’ll occasionally find them throughout Hyrule. I found the first one on Great Sky Island, south of Gutanbac Shrine, at coordinates (0620, -1654, 1503). Due to the cold, I didn’t notice it until I returned to Nachoyah Shrine and headed east.