Lilium

Liliaceae

Lily

Nearly all produce bulbs made up of loose scales and the flowers are borne singly or in loose groups. A few have rhizomatous bulbs where one or more bulbs grow along a basal rooting horizontal stem. They have light to dark green leaves which may be dense and grass-like or in others they are set in whorls  and are sword-shaped. The flowers are often fragrant and usually have six petals and well-defined stamens. The flower shape varies from the turban-shaped Turk's Cap with its re-curved petal margins to trumpet-shaped flowers and more open ones. Sizes also vary considerably from 2.5cm blooms to ones which are 30cm wide. Due to the complexity of the species a number of classification systems have been used to distinguish them. 
 

Uses

Mass plantings, mixed borders, rockeries, container plants, cut flowers.

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.
 

Cultivars

There are large numbers of cultivars, as well as many species that are widely grown. Some of the more popular species are:

L. amabile - to 120cm tall. They require spacing of 45cm. They bear Turks Cap flowers in summer which are red with black marks. They have a disagreeable odour. 
L. auratum  (Golden Rayed Lily) - large plants to 1.5 to 2.4m tall. These have fragrant, late summer bowl-shaped flowers to 30cm wide. They are stem rooting and good for pot culture. The flowers are white with a yellow band and raised purple spots inside. It is prone to virus diseases and there are some disease-resistant varieties available.
L. bulbiferum (Orange Lily) - to 60cm–120cm tall. They require spacing of 22.5cm. These bear summer trumpet-shaped flowers to6.5cm which are orange with purple spots. 
L. candadense (Canada Lily) - to 120cm–180cm tall. They require spacing of 30cm. They produce trumpet-shaped autumn flowers which are yellow with brown spots. 
L. hansonii (Golden Turk’s cap Lily) - to 120cm–150cm tall. They require spacing of 30cm. These bear yellow, waxy Turk's cap flowers with brown spots. The flowers are nodding, to 3cm long, and appear in midsummer. 
L. longiflorum (Easter Lily) - belongs to the sub-genus Eulerion, of the true lilies. The Easter Lily to 90cm tall with fragrant, white, trumpet-shaped summer flowers to 18cm long is the most popular lily for greenhouse pot lily production. 
L. regale - to between 1.2 and 2m tall. They produce fragrant, white, funnel-shaped summer flowers to 12.5cm long. The flowers have yellow centres and purple backs.  
L. speciosum - a similar height to L. auratum and are also stem rooting and suited to pot culture. They bear fragrant, bowl-shaped, white nodding flowers to 12.5 cm long which have recurved petals marked with red. There are a number of different coloured varieties which are sometimes scented.

 

Plant Health

Lilies are prone to botrytis (sometimes called lily disease) which is a fungal disease which spreads during warm and moist conditions. It is paticualrly troublesome during warm, humid conditions. The growing parts become brown and rot off. Other fungi cause basal rots. Blue mould can infect stored bulbs. Bulb rot is a fungus rot which develops in storage or in transit. It is confined to the base of the scales, which become detached from the basal portion of the bulb. Flowering stems are seldom produced, and if they develop they are usually stunted and inferior. Mosaic virus may cause discoloured and chlorotic leaves. Other virus diseases can affect Liliums causing distortion and blotching of foliage colour. Physiological disorders may be caused by poor cultural practices. 
Pests include aphids which attack all plant parts and bulbs in storage. They may spread virus diseases when they suck from the plant tissue. All parts may be eaten by slugs and millipedes. Leatherjackets may eat roots. Lily beetle larvae can also damage above ground parts. Nematodes are sometimes a problem. Thrips are not generally troublesome but in lily culture they may congregate occasionally in considerable numbers in some species. Bulbs may need to be soaked in a proprietary insecticide to control infestations.
 

More info

There are more than 80 species and hundreds of forms and hybrids which have been adapted for gardens. They mostly come from the Northern Hemisphere in Europe, Asia, India, and North America, most from cool temperate climates, but some from warmer areas.