Preheat the oven to 225°F (107°C). Line a baking sheet with parchment paper.
In a clean, dry mixing bowl, beat the egg whites with an electric mixer until soft peaks form. Add the cream of tartar and continue beating until stiff peaks form.
Gradually add the sugar, one tablespoon at a time, beating constantly until the meringue becomes glossy and smooth. Stir in the vanilla extract.
Add a few drops of green food coloring to the meringue and gently fold it in to create a light green color.
Spoon the meringue into a piping bag fitted with a star tip. On the prepared baking sheet, pipe out tree shapes, starting with a small base and making layers of meringue above it to form a conical tree shape.
Bake the meringue trees in the preheated oven for 1.5 to 2 hours, or until they are dry to the touch and easily peel away from the parchment paper. Turn off the oven and let the meringue cool completely in the oven with the door slightly ajar.
Once cooled, decorate the meringue trees with edible sprinkles, candy stars, or pearl dragees to give them a festive look.
Serve the meringue trees as delightful holiday treats!