The Chinese have long cultivated daylilies, both for their beauty and as food. The tubers are edible and used in salads or soups.
A typical plant produces 50 or more flowers during its blossoming season. Each blossom lasts only a day, accounting for the plant's common as well as its botanical name of Hemerocallis, meaning beauty for a day. Daylilies are perennials with tuberous, fleshy roots and arching, sword-shaped leaves.The lily-like flowers open in branched clusters at ends of generally leafless stems that stand well above foliage. The stems are 1 to 6 feet tall with 3- to 8-inch flowers. Daylily blooms are categorized as miniatures (less than 3 inches across), small (3 to 4 inches), and large (more than 4 inches).
Flower shapes are pinched, rounded or ornamental, and these may or may not have ruffles on the edges. Some flowers are single, and others are double. Daylilies come in many different colors and every shade, tone and tint possible, except pure white and true blue. The tetraploids are genetic variations with thick petals and deep colors.
The blooming season lasts three to four weeks and varies with the cultivar. It is divided into early (late May and June), middle (July), and late (August into September), although overlapping seasons occur.
Water daylilies as needed and fertilize them occasionally. Remove the flower stalks after their blossoms are spent to improve their appearance. Most varieties can be left alone, although some of the more vigorous ones bloom better if divided every few years.
Early feeding by aphids sometimes causes small warty bumps that appear on the backs of flower buds or on the fans and leaves. The most common symptom is a yellowing of the new foliage giving the appearance of nitrogen deficiency.
Control is difficult as the aphids are usually protected and cannot be controlled with a contact insecticide like insecticidal soap. For this reason a systemic insecticide is usually required.
Thrips are very small insects about the size and shape of an exclamation mark. They are likely to damage the flowers as they feed on small, developing buds causing distorted buds or streaking of the colored tissue. Control is difficult and also requires the use of a systemic insecticide.
Mite damage shows as whitish, stippled areas that eventually turn brown and die. Spider mites do not kill the plants outright but cause them to look like they are dying of drought.
Check by shaking the leaves over a piece of white paper. Watch the dust that falls on the paper. If it starts to crawl around, you have spider mites.
Spray the undersides of the leaves with water or insecticidal soap. If mites become more prevalent, use a miticide such as Kel-thane or Vendex. Many chemical insecticides kill the predator mites resulting in an epidemic of plant feeding mites.
Slugs and snails are also very fond of daylilies. They feed on tender young tissue causing ragged edges and holes. Sanitation, hand picking and baits are also effective. Grasshoppers also damage daylilies in areas where they feed heavi-ly.
Daylily diseases are not usually a problem because of our warm, dry climate. If the plants are overwatered they can develop crown rot. Grow daylilies on well-drained soil to prevent this problem. Unless a plant is rare or expensive, tubers that develop rot should be discarded.
Fungal leaf spots and blights are generally not a problem. If they develop spots or streaks on the leaves, avoid overhead watering or move the plants to a sunnier location with more air circulation. If symptoms persist, remove the plants to avoid spreading diseases.