Celia, just click on your plant list and then click on the 'Manage Categories' on the left side in the blue section. You'll now be on the 'Managing your categories' page. Scroll down and you'll see where you can create additional categories. Once you got that set up you can click on your list and then using the edit function on the right side, (pencil & pepper icon), you click to add it in the new category.
