Botany of the lily

What is a lily?

Botanical knowledge of the lily, without delving too deeply into the scientific aspects, is of equal importance for the amateur gardener, the professional horticulturist and the breeder.

Botanically, the lily belongs to the Monocotylcdoneae group, which have only one cotyledon, in contrast to the Dicotyledoneae, which have two. Monocotylcdoneae are divided into a number of other families, including one consisting of mainly bulbous plants, Liliaceae, to which the lily belongs. Apart from the genus Liliimi, a number of other decorative plants belong to the same family: Allium, Colchiaim, Ereinunis, and Convallaria.

A genuine lily (Lilium) is recognized by a number of features: 1. A bulb built up of a number of loosely overlapping scales but which, unlike the culinary onion (Allium cepa), are not covered with an outer membranous, protective skin 2. A leafy stem usually without leaves on the lower portion; one exception is the Madonna Lily 3. Lanceolate or linear leaves with parallel veins, not revolute or heart-shaped 4. A terminal flower or several flowers carried on pedicels, with a small leaf where the flower joins the main stem 5. A seed capsule which opens at the top, splitting down the middle of the three seed compartments and so releases the numerous flat, paper-like seeds for distribution by the wind

Near-relations of the genus Lilium are; Cardiocrinuiu, Notholirion, Nomocharis and Fritillaria. Neither Iris nor Aiithericum nor Hemerocallis are genuine lilies.

Bulbs and roots

Lilies, like narcissi, tulips or hyacinths, grow from bulbs which store plant nutrients, and can be likened to an underground bud. The bulb is the foundation and the life centre of the plant and consists of the basal plate, a compressed stem, and scales (1n reality a form of leaf) from which the flowering stalk, the flowers, and the roots grow. No plant or flower can ever be produced from a vermin-damaged or diseased basal plate.

The bulb scales contain starch particles which are easily seen under a microscope. The starch helps the stem and leaves to burst into growth during the spring, and when the leaves are sufficiently mature, they begin to assimilate. The assimilates (sugar) are returned to the bulb and converted back to starch. In fact, cooked lily bulbs taste like mashed potatoes, and are grown for food in China, Japan, and Siberia. The fleshy, comparatively small lily scales, lacking the protective coating of other bulbs, are easily damaged and apt to dry out quickly; great care must therefore be taken during packing, transporting, and planting.

Every bulb raised from seed illustrates that the bulb scales originate from leaves, in fact from the thicker and lower parts of the leaf sheath. L. candidum, L. formosanum, and the American L. catesbaei show this process exceptionally clearly.

The mostly strong and numerous roots spring from the base of the bulb (the basal plate) and draw both water and nutrients from the soil, in which they also help to anchor the bulb. The roots are contractile and able to draw the bulb deeper into the ground, making sure that it is at all times covered with a sufficient depth of soil. If, for instance, spring-sown L. regale seeds are covered with -inch of soil, the roots of the young bulbs will have drawn them to a depth of l-l inches by the following autumn. In its natural surroundings L. polyphyllum normally lies about I foot below the surface and has especially long roots to enable it to do so. The contractile roots of lilies provide another reason for planting bulbs, especially young, small ones, as early as possible in the autumn; it gives them a chance to root further before the onset of winter and ensures that the bulbs are well anchored in the soil and are not forced out by the cycle of frost and thaw.

The basal roots are usually 12-18 months old. New roots are mostly formed during late spring, although further and regular development takes place up until autumn. If roots break ofF during transplanting, or bulbs are bought with dry roots or, even worse, with none at all, the bulb is weakened for more than a year of its life.

Many lilies produce stem-roots which grow from the internodes nearest the bulb. In the main they absorb nutrients from the upper soil layers, mostly covered with compost provided by rotting vegetation, and feed it direct into the stem. This habit demonstrates the necessity for stem-roots to be kept covered with rich soil at all times. Stem-roots die off during the autumn and build up afresh during the following spring.

Not all bulbs are alike – there are three different types, and their growth-habits vary accordingly.

The concentric bulb

The scales in most lily bulbs are arranged in a concentric pattern; beginning from the centre of the bulb, scales are spirally arranged against and above each other, similar to the tiles on a house roof. This arrangement, and the ever-1ncreasing size of scales, from the bulb centre outwards, is easily seen in L. regale and L. davidii.

The development of new bulbs varies. With bulbs of Bulbiferum, Maculatum, and Hollandicum lilies, the growing stem splits the original bulb and the newly developing scales form two separate bulbs. This process is repeated regularly every year and makes it necessary to separate the increasing clumps of bulbs every second or third season. Other bulbs behave like those of L. regale, which form a growing centre around the stem for a new bulb that eventually pushes the old scales aside before it dies off, after a year or two.

Stoloniferous bulbs

The North American lilies, L. canadense, L. grayi, L. iridollae, L. michi-ganense, L. niichauxii, and L. superbuni, belong to this type; one or two underground stolons grow from a point where the stem leaves the bulb. They are finger-like and fleshy, forming, after f-1 ½ – inches growth, new bulbs with scales. In the course of only a few years a whole network of stolons, all terminating in bulbs, is built up, and, unless periodically divided and replanted, the heavy concentration of bulbs in a small area suffers from lack of space and plant food.

Rhizomatous bulbs

Several Pacific coast lilies grow a mass of scales on a rootstock. Among them are L. pardaliuum, L. maritimiitn, L. nevadense, L. harrisianum, L. occidentale, and L. parvum. New scales grow laterally, adjacent to the old ones, and are sometimes firmly, other times more loosely, connected to the original bulb they spring from. The only satisfactory way of parting them is with a sharp knife, which in the case of the American L. par-dalinum or L. harrisianum has to be done every three to four years if they are not to suffer from lack of plant food on account of their high density. Each of the newly formed rhizomatous bulbs produces a flowering stem during the subsequent growing year.

Rhizomatous lilies must not be confused with, for example, L. davidii and L. duchartrei. The flowering stems of these plants do not rise vertically from the bulb, but wander around underground before breaking through the soil surface. Bulbs, which produce shoots during the following year, are mostly developed at each node of that part of the stem which remains underground. Some lilies are conveniently multiplied in this way, but if L. duchartrei and L. lankongense are to be satisfactorily confined to their planting positions, without their flowering stems appearing in inconvenient nearby situations, they must be restricted, with a metal ring sunk into the ground, when they are first

Stems and leaves

The stem grows vertically upwards from the bulb every year and bears leaves which vary in form, colour, and arrangement according to variety. L. regale and L. centifolium have thickly growing, alternate, lanceolate leaves arranged spirally throughout the length of the stem. Many American lilies carry their leaves like L. martagon, which has a few broad-lanccolate leaves scattered on the upper parts of the stem, but the majority encireling it in one to three tiers of regularly spaced whorls. Comparatively broad-lanceolate and opposite leaves cover the stem of the Japanese L. auratuw, L. japouiewn, L. rubellum and L. speciosum. L. henryi, too, has similarly shaped leaves. The leaves of most lilies are smooth, shiny and green, but some have foliage with glandular hairs or leaves ciliate on the margins, exemplified by L. carniolicnm and its variety jankae and L. ciliatum.

Some lilies with small, grass-like leaves come from the dry, sunny steppes or from arid mountains. Good examples are L. pinniluni, L. cermium, L. callosum, and L. concolor. By contrast, lilies native to wooded areas and mountains subject to monsoons, like the Japanese varieties, have shiny, green, broad leaves.

The leaves soak up energy from the sun and, through photosynthesis by means of the chlorophyll, absorb carbon dioxide from the atmosphere; this, together with water, produces a new substance, similar to simple sugars. The plant uses the substance partly to maintain itself, and also to build up reserve nutrients in the bulb for future development. Excessive damage to or plucking of the leaves so vital to the plant’s food supply damages the bulb and jeopardizes its continuity. When cutting flowers, two-thirds of the leaves should be left on the growing plant. Botrytis, which attacks lily leaves and prevents them from functioning properly is for this reason very detrimental to growth and bulb development.

Flowers

The stem from a sound and healthy bulb produces one or more flowers. The floral envelope (perianth) consists of two groups of three tepals; the three outer ones correspond to sepals, and the three inner to petals. The similar outer and inner petals in monocotylcdonous plants are more correctly termed tepals, although for convenience they will be referred to as petals. They radiate from their base in symmetrical hexagonal form.

Flower display

Flowers are arranged in one of two ways, racemose or umbellate.

In the first case each flower in the head is arranged in a series; in L. davidii the flowers are arranged to look like a long candle; L. martagon and its hybrids look like a loose bunch of grapes; while in L. leticanthum var. centifolium the outline is the shape of a pyramid.

In contrast, the pedicels of the umbellate types all arise from the same level (L. bulbiferum, L. dauricum and Rainbow hybrids) and consequently show a larger and more concentrated area of colour.

There are deviations, notably among hybrids and varieties that give a mixture of both classes. The best effect is achieved by lilies with long, widely spaced, horizontal pedicels which permit full development of the individual blooms. L. regale flowers are positioned like a wheel in circular form on the extremity of the stem, and the plant seldom produces another one or two flowers at a different level. The similar L. sargentiae or, a better example, L. leucanthum var. centifolium, produces attractive, pyramid-shaped flower spikes. The delicate, slightly arched pedicels of L. canadense and of some other wild lilies of American origin create a truly beautiful and graceful picture. For the lily-breeder it is interesting to know that the umbelliferous flower arrangement is dominant.

Flower shapes

Flower shapes are divided into three classes: the Turk’s Cap, the saucer-shaped, and the funnel or trumpet-shaped.

L. martagon is the Turk’s Cap lily, but many Asiatic lilies bear flowers of the same shape, including L. davidii, L. cenmum, L. callosum, and L. henryi. So, of course, do the Bellingham hybrids and the American L. pardalinum and L. superbum.

Among the saucer-shaped, flowered types, with always erect and upright blooms, are the Asiatic L. dauricum and L. concolor, the European L. bulbifemm, and the American L. philadclphicum.

Funnel or trumpet-shaped flowers are borne by many Chinese lilies, L. regale, L. sargetitiae, L. sulphureuin, and L. wallichiamun. The funnel-shaped flowers of L. nepalense show this form but are wide open. Flowers are mostly horizontal or slightly pendant, with overlapping, recurved, or reflexed petals flaring out from a pipe-like tube into a funnel or trumpet shape.

Colour of flowers

The pigment available in the petals determines their colour. Varying shades of yellow are produced by carotene and flavinc; carotene is present not only in the epidermis but also in the mesophyll, while flavine confines itself to the upper epidermis. Red and blue are produced by various anthocyanins.

Carotene is capable of stronger and deeper pigmentation than flavine, and is responsible for the deep, sumptuous, yellow and orange colours. The many nuances of shades so admired in lilies are produced by a mixture of carotene, flavine and anthocyanin. Paper chromatography easily detects the presence of the different pigments in the flower.

Breeders are, of course, most interested and need to know if colours and individual pigments are inheritable and also if they are dominant (1.e., visible) or recessive (1.e., not apparent in the present generation but with a tendency to appear in a subsequent one).

The nectary furrows, occasionally surrounded by papillae as in L. henryi and L. spcciosiim, are shallow troughs at the base of the flower which secrete nectar in minute quantities.

The structure of the epidermis determines whether the flower has a shiny or a velvety appearance; the shiny petals have their cells evenly arranged in one plane, the velvety petals are in palisade form.

Stamens and carpels

The lily flower has six stamens, arranged in the shape of a hexagon. Each stamen consists of the filament growing from the base of the flower, and bears a pollen-filled anther at its apex. The vividly coloured stamens often project over and above the corolla; anthers usually open a few hours after the flower has begun to bloom, and release their pollen.

The female part of the flower, the pistil, consists of the ovary at the base of the flower, which contains three double-rowed seed cells, and the style and stigma. The style, like the filaments, is very long, and projects far outside the bloom. The stigma placed at the apex of the style shows its readiness to receive pollen by its damp, sticky appearance and often even drops of secretion. Pollination is effected by insects, particularly butterflies and moths that suck the nectar with their long proboscis, by shaking, by wind or through accidentally knocking the plant.

When the pollen is deposited on the stigma a long pollen tube travels down through the style to the ovules in the ovary and fertilizes the female egg cells. In order to fertilize every one of the 300-500 egg cells, an equal number of pollen grains must be deposited on the stigma and find their way to the ovary. If the pollen comes from more than one plant, egg cells are likely to be differently fertilized, and any subsequently produced seed will not be of uniform progeny.

Seed and seed capsules

Lilies have fairly large seed capsules of cylindrical or spherical shape, a few with wings along the ribs. The very large, elongated capsules of Cardiocrinum look most decorative when they open and reveal their toothed edge. The seeds of most lilies are thin and light, and easily distributed by wind as soon as the capsules split open into three parts, from the apex downwards. Cardiocrintim has the lightest and thinnest seeds, with a broad border of papery membrane around the periphery; those of L. martagon and the American lilies are more substantial, with no border of papery membrane; the seeds of the trumpet lilies are very thin and transparent, with a membranous border.

One seed capsule can contain 500 or more seeds, although some, because of unsuitable pollen, may contain only infertile seeds. The weight of seed varies widely; 700 L. Jienryi or L. martagon seeds weigh I ounce, but it takes twice as many L. davidii var. willmottiae seeds or 10 times as many L. regale seeds to make this weight.

Seeds are easily examined for quality by holding them against a light and looking for the embryo which, if present, appears in the form of a dark, slightly curved nucleus; if such an embryo is absent, the seed is infertile, and is not able to germinate. 4

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