Prepare several bags with icing in different shades of green and a variety of star tips.
Start by piping a row of stars at the bottom of the cone. With the bag straight up from the surface and the tip just above the surface, squeeze the bag to form a star. Stop squeezing before pulling the tip away. Use light pressure to form a small star; add more pressure to make a bigger star. Rotate the tip as you pipe around the cone.
Using different star tips and shades of green, pipe several clusters of stars, varying star sizes and colors. Cluster the stars tightly so that the cone is completely covered and does not show through.
Stop piping before reaching the tip of the cone. Holding the cone by the tip, place the tree on the iced board to position.