Once you reach the greenhouse you will first need to use the panel on the right to solve 3 puzzles and light the 1st 3 green lights. Below these 3 lights is a green button which will now power the heat lamp (the first 3 puzzles power the heat lamp and the other 3 will power the projector)
Push the lamp all the way to the left and then push the button below the 3 green lights to power the heat lamp and heal the 1st tree.
Now push the lamp to the right over the 2nd pot and plant your seeds. When you hit the button to heat the pot a sunflower will grow.
Now simply do the other tree and the giant Venus flytrap plant and the achievement should unlock