Adjective: Beginning to develop.

He's a budding deejay.

A newly sprouted leaf or blossom that has not yet unfolded.

After a long, cold winter, the trees finally began to produce buds.

(figuratively) Something that has begun to develop.

breast buds

(botany) A young plant grown from seed.

Any young plant, especially:

one grown in a nursery for transplanting.

a tree smaller than a sapling.

うーん、seedlingの方が「芽生え」という言葉で僕がイメージしてたものに近いかな

budも確かに新しく生えてきたものだけど、新しい葉や蕾を含むので「種から最初に生まれる」感じが少ない