Tall flowers are a popular choice for gardeners and landscapers alike. The two most common tall flowers are HOLLYHOCK (9 letters) and IRIS (4 letters). Hollyhocks are tall, flowering plants that come in a variety of colors and are often used to create a colorful backdrop in gardens. IRIS is a genus of flowering plants with sword-shaped leaves and showy flowers that come in a range of colors. Both hollyhocks and irises are popular choices for adding height and color to gardens.