The Woodland biome is the second Biome one will unlock in the game. There are three natural selection that can help you unlock this biome.

You can evolve a yellow Daisy to Buttercup.

If you've done the task Control a Sheep (which grants access to mushrooms) you can make a mud green Grass Tuft evolve to Oregano.

You can also make an Oak Tree Evolve to Sycamore Tree.