Cultivation of Daylilies
Daylilies are among the easiest of perennials to grow (provided their few essential requirements are met); however, difficulties may be experienced with some of the more inbred cultivars, especially those with complicated color patterns and heavy edge embellishments, if they are grown in climates very different from the ones in which they were bred. That said, most daylilies will fit seamlessly into the average garden provided they are given a place in the sun and a fertile soil. Daylily Bloom Time is April-July and Daylily Planting Time is May-September.
Soil
Daylilies grow best in well-drained, but moist, rich, friable loam, cultivated to a depth of about 45-60cm (18-24in). Best with a pH of about 6, they can also be grown successfully in soils well to either side of neutral, and will tolerate chalk, heavy clay or loose, sandy conditions, provided that generous supplies of organic material are incorporated into the soil and used as a mulch.
Heavy clay is the soil daylilies least like as it is usually very badly drained which could cause rotting. Drainage can be improved by adding copious amounts of coarse grit and organic manure, preferably in equal quantities by volume. In severely heavy soils land drains may be needed. An alternative strategy, used by many growers, is to plant daylilies in raised beds filled with imported top soil or compost.
Once loosened and rendered free -draining, a clay soil can be the ideal medium for daylilies since it is usually high in nutrients. Sandy soils are free-draining but the nutrients will quickly leach out. Like clay, sandy soils improve vastly with the addition of generous amounts of organic matter which helps to make it more water retentive. Regular mulching and extra nutrients are necessary, augmented by foliar feeds in early spring and as the buds are forming.
Planting
Daylilies can be planted at almost any time of the year, provided the ground is open, but local conditions may make a particular season preferable. Many growers recommend spring planting, especially in cold-winter areas since the plants will then have the summer weather during which to become established, making good roots before winter. Most growers in areas with severe winters keep autumn delivered daylilies in a greenhouse through winter. By late spring, when they are planted in the garden, they will already have produced flowers, seeds and scape increases and will often rebloom. Cultivation in the high temperatures of a greenhouse may produce uncharacteristic doubling of some daylilies, such as 'Elizabeth Salter'.
Other growers prefer autumn planting since the soil, having been heated by the sun all summer, will be warm, enabling the plants to make more rapid root growth. Most roots grow in soil temperatures of 2-18°C (35°F-65°F) and stop after 18°C (65°F). Generally speaking roots are happy at 8°C (15°F) less than the above ground parts of the plant. However, the roots of newly planted daylilies grow faster if their water requirements are met.
Autumn planting should be carried out at least six weeks before the predicted onset of frosts. Those daylilies that were in summer dormancy will make a spurt of growth in late summer and early autumn provided they have moisture, but it is not a good idea to plant evergreens recently received from hotter climates in the autumn. They should be potted until warmer weather returns. In the hottest regions, planting can be delayed until mid-autumn as there will be no fear of heavy frosts.
Planting is not recommended on hot summer days, but if unavoidable, the newly planted daylilies should be shielded from the direct rays of the sun.
A spacing of 60-90cm (2-3ft) is ideal if the daylilies are to remain in the same position for a number of years. If an immediate display of color is required plant about 45cm(18in) apart: daylilies planted this close will require earlier division.
The planting hole should be at least twice as large as the roots to be planted and never less than 45cm (18in) across by 23cm (9in) deep. The soil should be dug out and the bottom of the planting hole thoroughly broken up. Plenty of garden compost or farmyard manure should be incorporated into the soil before it is returned to the hole. This will provide all the immediate nitrogen (N) requirements. A fertilizer high in phosphorus and potassium (P, K) should also be added and will be taken up slowly by the daylily. Nitrogen moves through the soil more quickly so needs to be added more frequently.
The roots of most daylilies grow outwards and downwards leaving an area without roots immediately below the crown, so a small mound of soil should be left in the centre of the planting hole, to fill up this rootless space. Having positioned the daylily on the mound, firm the soil around the roots. If the daylily has become pot bound, its roots will need teasing out so that they are free to spread out over the mound of soil. Remove any dead or damaged roots at this time. The crown should be planted at the same level as that from whence it came, just deep enough to cover the non-green portion of the fan, not deeper than 2.5cm (1 in) in areas that have snow cover, or it may not bloom. Refill the hole with garden soil mixed with a potting mix. Make sure the soil mound is well tamped down before planting because if the crown sinks too low it may die.
If plants arrive with newly forming scapes, these should be cut off so that all the plant's energy goes into production of a healthy and vigorous root system. If new scapes appear about 2 months after planting keep just one so that the identity of the plant can be verified. Daylilies that are transplanted during reproductive or bloom periods may need some time before resuming active growth, but if transplanted just before or during their growing season, they will not take so long to establish. In any case it can take up to three years before plants exhibit their full potential.
Can daylilies change color from one year to the next? There are at least two ways in which this might appear to happen. One possibility is a "sport" from a mutant cell, which results in a portion of the clump producing flowers which are different from the originals in color and even shape. It is also possible, in a planting of several different varieties, for cross pollination to produce seed which sprouts and produces a new plant next to or intermingled with one of the original plants. A much less dramatic difference in color can result simply from temperature differences. Cooler temperatures produce more vibrant colors while hot weather can result in faded colors.