Daylilies are a group of plants in the genus Hemerocallis, including several species and many thousands of cultivars. These plants produce flowers that last for just a day, but they tend to produce many flowers on each scape, providing a relatively long bloom period.
Daylilies are tough and extremely adaptable. They are successfully grown in nearly any USDA hardiness zone, preferring full sun but tolerant of some shade.
Growing conditions 
Sun or Shade 
Flowers will be more prolific in better soil and in full sun. In heavy shade, foliage may be more abundant with few flowers. Daylilies prefer at least six hours a day for the paler shades, less for the darker reds and purples. If flowers fade, wilt or burn in direct sun, move them to filtered shade.
Daylilies can spread quickly in good soil (depending on the specific cultivar), so should be spaced appropriately. For large daylilies allow at least 18 to 20 inches between plants, 15 to 17 inches for medium size plants and 12 to 14 inches for small size plants. Daylilies should be planted high, never deeper than the crowns. If bare rooted plants are simply thrown on the ground, they sometimes root themselves in.
Soil Type 
A well-drained soil rich in organic material with a pH between 6 and 7 is recommended. Amend soils with compost, peat, good top soil, a little manure, and / or other available organic material. Mix the added materials with a garden fork to the depth of the fork. Spending time and money on your soil is always a good investment.
Select the appropriate daylily varieties for your climate. While most daylilies will grow in a wide variety of climates, some are best suited for specific areas. Because most of the daylilies grown today are hybrids of dormant and evergreen species, they can be categorized into these three groups depending on whether they lose their foliage during the dormant season. Daylilies are divided into three general categories:
- Evergreen - cultivars that retain their foliage throughout the year. Especially popular in mild climates, but grown widely.
- Semi-evergreen - cultivars that tend to lose most of their foliage during the winter. Adaptable to a wide variety of climates.
- Dormant - cultivars that lose their foliage entirely during the winter. Especially adaptable to cold climates but will grow well in all except the most tropical environments.
- Early Spring
- In early spring, daylilies should be cut back to within 5 cm (2 in.) on the soil line or the base of the crown. They will appreciate a good layer of mulch.
- Bloom Period (mid-summer)
- During bloom, these plants need a consistently moist soil, otherwise the buds may fail to open or the flowers will be dwarfed. Overhead irrigation or rain will mottle or "melt" the day's blooms, so irrigation should either be done by hand, drip, or in the late afternoon when the day's flowers have begun to fade.
- Many daylilies also need to be deadheaded, meaning the spent flowers must be removed by pinching off or cutting. Particularly on large-flowered varieties, the spent flowers may get wrapped around other buds, preventing them from opening properly. Many newer cultivars are "self-deadheading", meaning that the flowers drop by themselves rather than needing to be pinched or cut. Care must be taken with some varieties, as the spent blooms closely resemble opening buds.
- After Blooming
- After blooming, most daylilies put on a new flush of vegetative growth. The old foliage is often yellow and unattractive, so it is often removed. This can be done either by pulling the old leaves out, or simply cutting the plant to the ground (they quickly regrow).
- Fall Cleanup
- After the foliage goes completely yellow, it is best to cut back the foliage to within 20 cm (8 in.) of the soil line, to prevent matting during the winter months. While this is not necessary, it makes for a more attractive winter garden and eliminates a potential harbor for undesirable pests and fungi. At a minimum, remove the spent, brown flower scapes.
Daylilies are usually propagated by division, and are one of the easiest perennials to divide. There are several methods for dividing daylilies:
- The most common method is to take two digging forks, inserted through the middle of the clump back to back, and simply prying the plant apart.
- For very large clumps, daylilies can also be divided by either driving a shovel or spade throught the clump while still in the ground, or else the clump can be dug up and cleaved with an axe or mattock.
- For special cultivars, daylilies can be divided by hand, using fingers and a knife.
Divisions can be as small as a single fan.
A proliferation is a small fan that grows in the node of a bract on the scape. These fans can be rooted to make a new plant (which will, like divisions, be a clone). To encourage proliferations, simply make sure that no seed pods are allowed to develop on the top of the scape. Harvest the proliferations as soon as the scape shows signs of yellowing, and root in water with a piece of the scape still attached.
Tissue Culture 
Some of the newer, patented cultivars of daylily are propagated through tissue culture.
Seed Propagation 
Many daylily cultivars can produce fertile seed (however, triploid cultivars do not). To harvest seed, simply leave the seed pod on the plant until it completely dries up and opens. Some prefer to harvest a little earlier, but at least wait until the pod shows some sign of an open crack. The time from pollination to harvest runs around 45 days.
Daylily seeds are easy to gather, but not all seeds are fertile. Some plants may be sterile and never produce seeds, some may be fertile one way or both ways.
When seed pods turn brown and start to split, gently remove seeds. Jason will tie a bag over the flowers he pollinated to catch the seed, and leave the pod on the stem as long as possible. Seeds should dry (at least one month is recommended) before refrigerating or planting.
Germinate seeds approximately two weeks in any suitable germinating mixture. Cover seeds to a 1/8 to 1/4 inch depth. Place containers in partial shade to prevent drying out. Transplant when adequate roots develop and wait two to three years for a flower.
To properly hybridize a new registered daylily will take some patience and persistence, but since each seed-grown daylily is different from every other daylily in the world, even a beginning gardener can help create a brand new flower.
The buds and flowers of the daylily are edible, and used in some Asian cuisines. They can also be stuffed, similar to Squash flowers.
The difficulty with daylilies is that since the blooms only last a day, they must be picked and used the same day. The best time to pick is just after the flowers have fully opened. Refrigeration is not appropriate, as it will cause them to wilt.
The enlarged roots can be peeled and eaten raw or stir-fried. They have a sweet radish flavor.
Pests and diseases 
Fungal Diseases 
- Leaf Spot caused by Cercospora hemerocallis
- Russett Spot
- Leaf Streak caused by Aureobasidium microstictum
- Crown Rot (Southern Blight) caused by Sclerotium rolfsii
- Rust caused by the heteroecious fungus Puccinia hemerocallidis (alternate host: Patrina.
- Root Knot caused by the Southern Root Knot Nematode (Meliodgyne incognita):
Insects, Mites 
- A plant bug (Lopidea confluenta)
- Thrips, including
- Flower Thrips (Frankliniella tritici)
- Western Flower Thrips
- Daylily Thrips
- Hemerocallis Gall Midge
- Beetles, including
- Imported Longhorned Weevil
- Japanese Beetle
- Bumble Flower Beetle
- Convict Caterpillar
- Two-spotted Spider Mite (Tetranychus urticae)
Other Animals 
- Slugs and Snails
- White Tailed Deer
Unknown Cause 
- Spring Sickness (see About Spring Sickness)