Here is the full list of all 19 A meadow Piece achievements.
more than 50 flowers are on the meadow
more than 100 flowers are on the meadow
let a pure white flower grow
let a pure red flower grow
let a pure green flower grow
let a pure blue flower grow
let a pure black flower grow
survive 1 Alien
survive 10 Aliens
survive 20 Aliens
survive 30 Aliens
activate a colored marking with the similar petal color as a main flower
activate a white marking with the same number of petals as a main flower
survive another player
play with four players simultaneously
activate the green circle for four players simultaneously
call a bug
call a friend for a bug
bring a sphere flower far away from the center