botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek w ...

, a bulb is structurally a short stem with fleshy

leaves A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

or leaf basesBell, A.D. 1997. ''Plant form: an illustrated guide to flowering plant morphology''. Oxford University Press, Oxford, U.K. that function as food

storage organ A storage organ is a part of a plant specifically modified for storage of energy (generally in the form of carbohydrates) or water. Storage organs often grow underground, where they are better protected from attack by herbivores. Plants that have ...

s during dormancy. (In

gardening Gardening is the practice of growing and cultivating plants as part of horticulture. In gardens, ornamental plants are often grown for their flowers, foliage, or overall appearance; useful plants, such as root vegetables, leaf vegetables, fruits ...

, plants with other kinds of storage organ are also called "

ornamental bulbous plant Ornamental bulbous plants, often called ornamental bulbs or just bulbs in gardening and horticulture, are herbaceous perennials grown for ornamental purposes, which have underground or near ground storage organs. Botanists distinguish between ...

s" or just "bulbs".)

Description

The bulb's leaf bases, also known as

scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number w ...

, generally do not support leaves, but contain food reserves to enable the plant to survive adverse conditions. At the center of the bulb is a vegetative growing point or an unexpanded flowering shoot. The base is formed by a reduced stem, and plant growth occurs from this basal plate. Roots emerge from the underside of the base, and new stems and leaves from the upper side. Tunicate bulbs have dry, membranous outer scales that protect the continuous lamina of fleshy scales. Species in the genera ''

Allium ''Allium'' is a genus of monocotyledonous flowering plants that includes hundreds of species, including the cultivated onion, garlic, scallion, shallot, leek, and chives. The generic name ''Allium'' is the Latin word for garlic,Gledhill, David ...

'', ''

Hippeastrum ''Hippeastrum'' () is a genus of about 90 species and over 600 hybrids and cultivars of perennial herbaceous bulbous plants. They generally have large fleshy bulbs and tall broad leaves, generally evergreen, and large red or purple flowers. ...

'', ''

Narcissus Narcissus may refer to: Biology * ''Narcissus'' (plant), a genus containing daffodils and others People * Narcissus (mythology), Greek mythological character * Narcissus (wrestler) (2nd century), assassin of the Roman emperor Commodus * Tiberiu ...

'', and '' Tulipa'' all have tunicate bulbs. Non-tunicate bulbs, such as '' Lilium'' and '' Fritillaria'' species, lack the protective tunic and have looser scales. Bulbous plant species cycle through vegetative and reproductive growth stages; the bulb grows to flowering size during the vegetative stage and the plant flowers during the reproductive stage. Certain environmental conditions are needed to trigger the transition from one stage to the next, such as the shift from a cold winter to spring. Once the flowering period is over, the plant enters a foliage period of about six weeks during which time the plant absorbs nutrients from the soil and energy from the sun for setting flowers for the next year. Bulbs dug up before the foliage period is completed will not bloom the following year but then should flower normally in subsequent years.

Plants that form bulbs

Plants that form underground

s, including bulbs as well as

tuber Tubers are a type of enlarged structure used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growing ...

s and

corm A corm, bulbo-tuber, or bulbotuber is a short, vertical, swollen underground plant stem that serves as a storage organ that some plants use to survive winter or other adverse conditions such as summer drought and heat (perennation). The word '' ...

s, are called ''geophytes''. Some epiphytic

orchid Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Along with the Asteraceae, they are one of the two largest families of flowering ...

s (family Orchidaceae) form above-ground storage organs called ''

pseudobulb The pseudobulb is a storage organ found in many epiphytic and terrestrial sympodial orchids. It is derived from a thickening of the part of a stem between leaf nodes and may be composed of just one internode or several, termed heteroblastic and ...

s'', that superficially resemble bulbs. Nearly all plants that form true bulbs are

monocotyledon Monocotyledons (), commonly referred to as monocots, ( Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one embryonic leaf, or cotyledon. They constitute one of ...

s, and include: * ''

Amaryllis ''Amaryllis'' () is the only genus in the subtribe Amaryllidinae (tribe Amaryllideae). It is a small genus of flowering bulbs, with two species. The better known of the two, ''Amaryllis belladonna'', is a native of the Western Cape region of ...

'', ''

Crinum ''Crinum'' is a genus of about 180 species of perennial plants that have large showy flowers on leafless stems, and develop from bulbs. They are found in seasonally moist areas, including marshes, swamps, depressions and along the sides of strea ...

'', ''

'', and several other members of the amaryllis family

Amaryllidaceae The Amaryllidaceae are a family of herbaceous, mainly perennial and bulbous (rarely rhizomatous) flowering plants in the monocot order Asparagales. The family takes its name from the genus ''Amaryllis'' and is commonly known as the amaryllis fam ...

. This includes onion, garlic, and other

allium ''Allium'' is a genus of monocotyledonous flowering plants that includes hundreds of species, including the cultivated onion, garlic, scallion, shallot, leek, and chives. The generic name ''Allium'' is the Latin word for garlic,Gledhill, David ...

s, members of the Amaryllid subfamily

Allioideae Allioideae is a subfamily of monocot flowering plants in the family Amaryllidaceae, order Asparagales. It was formerly treated as a separate family, Alliaceae. The subfamily name is derived from the generic name of the type genus, ''Allium''. ...

. *

Lily ''Lilium'' () is a genus of herbaceous flowering plants growing from bulbs, all with large prominent flowers. They are the true lilies. Lilies are a group of flowering plants which are important in culture and literature in much of the world. M ...

, tulip, and many other members of the lily family

Liliaceae The lily family, Liliaceae, consists of about 15 genera and 610 species of flowering plants within the order Liliales. They are monocotyledonous, perennial, herbaceous, often bulbous geophytes. Plants in this family have evolved with a fair ...

. * Two groups of ''

Iris Iris most often refers to: *Iris (anatomy), part of the eye *Iris (mythology), a Greek goddess * ''Iris'' (plant), a genus of flowering plants * Iris (color), an ambiguous color term Iris or IRIS may also refer to: Arts and media Fictional ent ...

'' species, family Iridaceae: subgenus '' Xiphium'' (the "Dutch" irises) and subgenus ''

Hermodactyloides The subgenus ''Hermodactyloides'' of Iris includes all reticulate-bulbed bulbous irises. It was formerly named as a genus, ''Iridodictyum'' by Rodionenko in 1961. but it was not widely accepted and most botanists preferred 'Hermodactyloides'. � ...

'' (the miniature "rock garden" irises). ''

Oxalis ''Oxalis'' ( (American English) or (British English)) is a large genus of flowering plants in the wood-sorrel family Oxalidaceae, comprising over 550 species. The genus occurs throughout most of the world, except for the polar areas; species d ...

'', in the family Oxalidaceae, is the only

dicotyledon The dicotyledons, also known as dicots (or, more rarely, dicotyls), are one of the two groups into which all the flowering plants (angiosperms) were formerly divided. The name refers to one of the typical characteristics of the group: namely, t ...

genus that produces true bulbs.

Bulbil

bulbil A bulbil (also referred to as bulbel, bulblet, and/or pup) is a small, young plant that is reproduced vegetatively from axillary buds on the parent plant's stem or in place of a flower on an inflorescence. These young plants are clones of the par ...

is a small bulb, and may also be called a bulblet, bulbet, or bulbel. Small bulbs can develop or propagate a large bulb. If one or several moderate-sized bulbs form to replace the original bulb, they are called renewal bulbs. Increase bulbs are small bulbs that develop either on each of the leaves inside a bulb, or else on the end of small underground stems connected to the original bulb. Some lilies, such as the tiger lily ''

Lilium lancifolium ''Lilium lancifolium'' (syn. ''L. tigrinum'') is an Asian species of lily, native to China, Japan, Korea, and the Russian Far East. It is widely planted as an ornamental because of its showy orange-and-black flowers, and sporadically occurs a ...

'', form small bulbs, called bulbils, in their leaf

axil A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

s. Several members of the onion family, Alliaceae, including ''Allium sativum'' ( garlic), form bulbils in their flower heads, sometimes as the flowers fade, or even instead of the flowers (which is a form of

apomixis In botany, apomixis is asexual reproduction without fertilization. Its etymology is Greek for "away from" + "mixing". This definition notably does not mention meiosis. Thus "normal asexual reproduction" of plants, such as propagation from cuttin ...

). The so-called

tree onion The tree onion (''Allium'' × ''proliferum'') is a perennial plant similar to the common onion (''A. cepa''), but with a cluster of bulblets where a normal onion would have flowers. Tree onions are also known as topsetting onions, walking ...

(''Allium'' × ''proliferum'') forms small onions which are large enough for pickling. Some ferns, such as the hen-and-chicken fern, produce new plants at the tips of the fronds' pinnae that are sometimes referred to as bulbils. Image:Lilium lancifolium bulbils.jpg, Bulbils form in the leaf axils of ''

'' Image:Alliumvineale1web.jpg, Wild garlic (''

Allium vineale ''Allium vineale'' (wild garlic, onion grass, crow garlic or stag's garlic) is a perennial, bulb-forming species of wild onion, native to Europe, northwestern Africa and the Middle East. The species was introduced in Australia and North America, ...

'') bulbils sprouting Image:Allium fistulosum bulbifera0.jpg, "

Tree onion The tree onion (''Allium'' × ''proliferum'') is a perennial plant similar to the common onion (''A. cepa''), but with a cluster of bulblets where a normal onion would have flowers. Tree onions are also known as topsetting onions, walking ...

s" form clusters of small bulbs instead of flowers

Description

Plants that form bulbs

Bulbil

See also

References

Further reading