Flowering borders and edging plants. In gardening, a border or edging plant refers to a specific type of plant that is commonly used to create boundaries or borders within a garden bed or along pathways. These plants are typically shorter in height compared to other plants in the garden and are strategically placed to form a decorative edge or mark out different areas. The right height for a border is all about the scale compared to the rest of the garden bed or area. To keep it simple, we’re include here only plants that reach a height of up to 50cm or 1.5 feet. Larger flowering plants for a layered garden bed can be found in the Cottage Perennials & Annuals and Shrubs categories.