stone leek, Welsh onion
葱 refers to a specific type of onion: the stone leek or Welsh onion, a long green onion used in cooking.
葱 combines the grass radical 艹 with 怱, which likely contributes the sound. The character is used for a type of onion, but the exact historical development of the components is uncertain.
The grass radical 艹 sits above a shape that looks like a hurried heart 怱. Imagine a bunch of green onions growing so fast they look hurried—those are Welsh onions.
For ソウ, picture a long green onion being sown like a seed: sow -> ソウ, and the onion grows quickly under the grass.
Welsh onion (Allium fistulosum); Japanese bunching onion; green onion; spring onion; scallion
pale blue-green
chive (Allium schoenoprasum); chives
Alpine leek (Allium victorialis var. platyphyllum)
leek (Allium porrum)
Welsh onion (Allium fistulosum); Japanese bunching onion
tree onion (Allium x proliferum)
heartshape false pickerelweed (Monochoria vaginalis)
light light blue; pale blue
Monochoria korsakowii (species of flowering plant)
chestnut tiger butterfly (Parantica sita)
pale blue-green
blue-green lining; kimono with blue-green lining
white squill (Urginea maritima); sea onion
tuna minced with Welsh onion leaves (type of sushi topping)
green onion pancake
onion flower head
scallion oil
scallion pancake; green onion cake
chicken and scallion skewer