The plants of the genus Lilium are the true lily plants, comprising a genus of about 100 species in the lily family, Liliaceae. They are important as showy and large flowered garden plants, and in literature.

Lilies are native to the northern temperate regions. Their range in the Old World extends across much of Europe, the north Mediterranean, across most of Asia to Japan, south to the Nilgiri mountains in India, and south to the Philippines. In the New World they extend from southern Canada through much of the United States. A few species formerly included within this genus have now been placed in other genera. These include Cardiocrinum and Nomocharis.

Description

Lilies are usually erect leafy stemmed herbs. The majority of species form naked or tunic-less scaly underground bulbs from which they overwinter. In some North American species the base of the bulb develops into rhizomes, on which numerous small bulbs are found. Some species develop stolons. A few species form bulbs at or near the soil surface .

Many species form stem-roots. With these, the bulb grows naturally at some depth in the soil, and each year the new stem puts out adventitious roots above the bulb as it emerges from the soil. These roots are in addition to the basal roots that develop at the base of the bulb.

The large flowers have three petals along with three petal-like sepals, often fragrant, and come in a range of colours ranging through whites, yellows, oranges, pinks, reds, purples, bronze and even nearly black. Markings include spots, brush strokes and picotees.

The plants are summer flowering. Most species are deciduous, but Lilium candidum bears a basal rosette of leaves for much of the year. Flowers are formed at the top of a single erect stem, with leaves being borne at intervals up the stem.

Growing conditions

They are commonly adapted to either woodland habitats, often mountain, or sometimes to grassland habitats. A few can survive in marshland and a single one is known to live as an epiphyte (L. arboricola). In general they prefer moderately acidic or lime-free soils.

Species

Asiatic hybrid flower

Numerous forms are grown for the garden, and most of these are hybrids. They vary according to their parent species, and are classified in the following broad groups;

• Species (Division IX). All natural species and naturally occurring forms are included in this group.
• Asiatic hybrids (Division I). These are plants with medium sized, upright or outward facing flowers, mostly unscented. They are derived from central and east Asian species.
• Martagon hybrids (Division II). These are based on L. martagon and L. hansonii. The flowers are nodding, Turk's cap style (with the petals strongly recurved).
• Candidum hybrids (Division III). This includes hybrids of L. candidum with several other mostly European species.
• American hybrids (Division IV). These are mostly taller growing forms, originally derived from L. pardalinum. Many are clump-forming perennials with rhizomatous rootstocks.
• Longiflorum hybrids (Division V). These are cultivated forms of this species and its subspecies. They are most important as plants for cut flowers, and are less often grown in the garden than other hybrids.
• Trumpet lilies (Division VI), including Aurelian hybrids. This group includes hybrids of many Asiatic species, including L. regale and L. aurelianse. The flowers are trumpet shaped, facing outward or somewhat downward, and tend to be strongly fragrant, often especially night-fragrant.
• Oriental hybrids (Division VII). These are based on hybrids of L. auratum and L. speciosum, together with crossbreeds from several mainland Asiatic species. They are fragrant, and the flowers tend to be outward facing. Plants tend to be tall, and the flowers may be quite large. An example is w:Lilium "Stargazer".
• Other hybrids (Division VIII). Includes all other garden hybrids.

Uses

Many species are widely grown in the garden in temperate and sub-tropical regions. Sometimes they may also be grown as potted plants. A large number of ornamental hybrids have been developed. They can be used in herbaceous borders, woodland and shrub plantings, and as a patio plant.

Some lilies, especially Lilium longiflorum, as well as a few other hybrids, form important cut flower crops. These tend to be forced for particular markets; for instance, L. longiflorum for the Easter trade, when it may be called the Easter lily.

Lilium bulbs are starchy and edible as root vegetables, although bulbs of some species may be very bitter. The non-bitter bulbs of Lilium lancifolium, Lilium pumilum, and especially Lilium brownii (called 百合干 in Chinese) are grown at large scale in China as a luxury or health food, most often sold in dry form. They are eaten especially in the summer, for their ability to reduce internal heat. They may be reconstituted and stir-fried, grated and used to thicken soup, or processed to extract starch. Their texture and taste draw comparison with the potato, although the individual bulb scales are much smaller.

Although they are believed to be safe for humans to eat, there are reports of nephrotoxicosis (kidney failure) in cats which have eaten some species of Lilium and Hemerocallis .

Lilies are considered the most common of flowers to be presented at funerals. The presence of Lilies at funerals symbolizes that the soul of the departed has received restored innocence after death.

Maintenance

Maintaining Asian lilies means as a basic rule to keep the bulbs cool and not watered in winter. More than just some basic moisture might cause the bulb to rot.

Propagation

Liliums can be propagated in several ways;

• by division of the bulbs,
• by growing-on bulbils which are adventitious bulbs formed on the stem,
• by scaling, for which whole scales are detached from the bulb and planted to form a new bulb,
• by seed; seed germination patterns are variable and can be complex.

Harvesting

Pests and diseases

Soft Rot

• Erwinnia carotovora

Gray Mold

• Botrytis cinerea
• Botrytis elliptica

Stem Rot

• Phytophthora parasitica

Stem Canker

• Pellicularia filamentosa

Wilt

• Pelicularia rolfsii
• Sclerotium delphinii

Foot Rot

• Phytophthora cactorum

Soft Bulb Rot

• Rhizopus stolonifer
• Rhizopus

Blue Mold

• Penicilium corymbiferum
• Penicillium cyclopium

Bulb Rot

• Fusarium oxysporum var. lilii

Brown Scale

• Colletotrichum lilii

Rusts

• Puccinia sporoboli
• Uromyces holwayi

Viri

• Cucumber Mosaic Virus
• Lily Symtomless Virus
• Tobacco Ringspot Virus
• Mottle Virus
• Lily Rosette Virus

Nematodes

• Bulb and Leaf Nematode: Aphelenchoides fragariae
• Root Lesion Nematode: Pratylenchus penetrans
• Root Lesion Nematode: Pratylenchus praetensis

Physiological problems

• Bud Blast
• Chlorosis
• Frost Injury
• Leaf Scorch

Aphids

• Melon Aphid: Aphis gossypii
• Crescent Marked Lily Aphid: Neomyzus circumflexus
• Green Peach Aphid: Myzus persicae
• Foxglove Aphid: Acyrthosiphon solani

Scales

• Hemispherical Scale: Saissetia coffae

Whiteflies

• Greenhouse Whitefly: Trialeurodes vaporariorum

Thrips

• Thrips: Liothrips vaneechei
• Thrips: Taeniothrips simplex
• Gladiolus Thrips: Thrips simplex

Flies

• Lesser Bulb Fly: Eumerus tuberculatus
• Narcissus Bulb Fly: Merodon equestris

Beetles

• Lily Weevil: Agasphaerops nigra
• Rugose Strawberry Weevil: Brachyrhinus rugostriatus
• Lily Leaf Beetle: Lilioceris lilii
• Strawberry Root Weevil: Otiorhynchus ovatus
• Black Vine Weevil: Otiorhynchus sulcatus
• Fuller Rose Beetle: Pantomorus cervinua

Caterpillars

• Stalk Borer: Papaipema nebris
• Saddleback Caterpillar: Sibine stimulea
• The Dun-bar

Mites

• Bulb Mite: Rhizoglyphus echinopus

References

• Britton, Nathaniel Lord; Addison Brown (1913). An Illustrated Flora of the Northern United States and Canada, Volume 1 (second edition ed.). Dover Publications, inc.. pp. 502–504. 
• Ann Fowler Rhoads and Timothy A. Block (2000). The Plants of Pennsylvania: An Illustrated Manual. Anna Anisko, illustrator. Morris Arboretum, University of Pennsylvania Press. pp. 863–864. 
• P. D. Strausbaugh and Earl L. Core (1977). Flora of West Virginia (Second ed.). Seneca Books, Grantsville, W. Virginia. pp. 234–235. 
• Christopher Brickell and Judith D. Zuk (1997). The American Horticultural Society A-Z Encyclopedia of Garden Plants. DK Publishing. pp. 612–618. 
• Staff of the L. H. Bailey Hortorium (1976). Hortus Third: A Concise Dictionary of Plants Cultivated in the United States and Canada. Cornell University Press. pp. 658–664. 
• Pirone, Pascal P. (1978). Diseases & Pests of Ornamental Plants (Fifth Edition ed.). John Wiley & Sons, New York. pp. 343–347. 
• Cranshaw, Whitney (2004). Garden Insects of North America: The Ultimate Guide to Backyard Bugs. Princeton University Press. pp. 604. 
• Pippa Greenwood, Andrew Halstead, A.R. Chase, Daniel Gilrein (2000). American Horticultural Society Pests & Diseases: The Complete Guide to Preventing, Identifying, and Treating Plant Problems (First Edition ed.). Dorling Kindersley (DK) Publishing, inc.. pp. 200.