芽立ち is read as めだち (medachi) and means bud.
めだち
medachi
め
germinal disk (in an egg)
めばえ
bud
めばえる
to arise
めぶく
to bud
がじょうへんい
bud mutation
めだし
sprouting
がせい
gemmation
めをだす
to sprout
がたい
blastema
がきゅう
blast (cell)
すだち
leaving the nest
ひとりだち
standing on one's own feet (without the use of crutches, etc.)