The day lily is an attractive flower that grows from a mound of slender, bright-green leaves. The flower appears at the top of a stalk that is usually 1 ½ to 2 feet long, though it can be much longer. Each stalk has multiple buds on it, and each bud opens into a colorful day lily, generally at different times. The day lily flower only blooms for a single day, but each plant will produce a profusion of blooms throughout the season. There are many varieties of day lilies. These are categorized into different types, based on appearance.
Spider day lilies have long, slender petals. The ratio of length to width on these petals must be at least 4 to 1, according to the American Hemerocallis Society, an organization that promotes day lilies, provides information, and sponsors and organizes flower shows. Spider day lilies, as with all day lilies, exist in many colors, including red, yellow and orange. This group includes such lilies as the Amethyst Squid, among many others.
Double daylilies, often referred to simply as doubles, are flowers with an abundance of petals. There are two main types of these: the ‘Peony-type’, with stamens that look like petals within the flower, and the ‘Hose-in-Hose’ type, with the petals arranged so that it appears there is actually a flower within a flower. Doubles have a wide range of color options. Double flowers like ‘A Ba Ba Rum’ have multiple colors on a single flower. (REF 2, 4)
A polymerous daylily is one that has more than the three sepals, or segments, than are normal for a day lily. These flowers usually have four or five sepals in the outer whorl. The inner whorl also has an increased number of petals, which usually corresponds to the number of sepals. The bright yellow Awaba Sunray is an excellent example of this type of day lily.
Day lilies come in many other types as well. Single day lilies have three petals and three sepals. They may sometimes share some of the characteristics of other types of day lilies, such as being polymerous or double. "Unusual form" day lilies is a term that describes a class of these flowers, based entirely upon the appearance of the petal or sepal shapes. They may be pinched, cascade or be spatulate, but in order to qualify as an unusual form day lily, the flower must have the shape on a minimum of 3 petals or stamens. Daylilies classed as multiform must combine two or more features of the double, spider, polymerous or unusual form lilies. All of these types of day lilies are available in many different colors and sizes.