Culture
Early summer is the usual growing season, and most are suitable to be grown in many different climates. They are best planted in autumn through to early spring. They prefer well-drained soil and so do well on sloping sites. Indeed, good drainage is essential. Heavy soils will support the growth of liliums, but only where they are well-drained. Sandy soils built up with lots of compost may be better if you have the choice. Most do well in any soil but a few are more particular with regards to acidity or alkalinity. Generally, a pH of 6.5 suits most species. They will thrive in soils enriched with organic matter. Apply organic mulch annually. Water well during the growing season.
Plant stem-rooting types deeper than base-rooting types, and to two and a half times the height of the bulb. In poorly drained soils, stem rooting types should be planted shallower. Both types may do better with only 15cm of soil covering the bulb, if the soil is poorly drained, otherwise you need around 25cm of soil for base-rooting types and deeper for stem-rooting types.
Liliums thrive in full sun to part shade. All types should be protected from strong winds and excessive heat or cold. When they flower, support arching flowers with stakes or canes. Weed control is also important.
Propagation
The easiest method of propagation is division of overcrowded clumps every few years during autumn to early spring. Liliums do not store well over time, in fact they do not enter a completely ‘dormant phase’. As such there should be minimal time between lifting, dividing and replanting, or use of cold storage is necessary. Typically, bulbils are replanted immediately after division. If you only want to produce small quantities, this may be the most appropriate technique but for larger quantities, tissue culture or bulb scale cuttings are more productive techniques. A major consideration is to propagate new plants free of virus. This is difficult unless you have virtually total control of aphids (the main culprit in transmitting viral diseases).
Almost all varieties of liliums can be grown successfully from scales (bulb cuttings). Bulb scale cuttings are best carried out with the bulb in its semi-dormant phase (usually late summer to early winter). The Lilium bulbs should be lifted as soon as the plants die back, and the bulbs thoroughly cleaned of any dirt or debris. Use only healthy bulbs with no sign of pest or disease problems. Individual scales are carefully detached from the bulb, as close as possible to the basal plate (it is not essential to retain a section of the basal plate). The scales should be well dusted with a suitable fungicide. These scales are planted in a well drained propagating mix with tips (top) just showing through the surface. One or two bulbils will normally be produced per scale, depending on conditions. Ideally keep at approximately 23°C (16°C is required for even minimal growth). Alternatively the scales can be placed into just moist vermiculite, peat moss, shredded sphagnum moss, or similar material, then sealed in a polythene bag, and placed in a dark, warm place for 6–8 weeks at around 20°C. Tiny bulbils will develop at the base of the scales. The polythene bags are then transferred to a cool position (i.e. bottom compartment of a refrigerator) and kept at 1-4°C for 2-3 months. The bulbils are then removed and planted out into suitable beds or containers. Stem-rooted liliums need to be planted out deeper, in accordance with the natural root formation of these types of plants.
Liliums may also be grown from seeds sown in autumn although hybrids rarely grow true to type but will vary in flower and other characteristics. Even where the seed is all collected from the same plant, the seedlings could produce a range of different types of plants, some more useful than others, and you won’t know the differences until they all flower. Seedlings often take several years to flower.