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thickened, fleshy plant bud, usually formed under the surface of the soil, which carries the plant over from one blooming season to another. It may have many fleshy layers (as in the onion and hyacinth) or thin dry scales (as in some lilies)—both of which are highly modified leaves. Many popular outdoor and house plants, such as the tulip and the narcissus, are grown from bulbs, often out of their usual flowering season by forcing (i.e., by exposing them to a cold treatment). Not true bulbs, but often so called, are the cormcorm,
short, thickened underground stem, usually covered with papery leaves. A corm grows vertically, producing buds at the upper nodes and roots from the lower surface. Corms serve as organs of food storage and in some plants (e.g.
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 of the crocus and the gladiolus, the tubertuber,
enlarged tip of a rhizome (underground stem) that stores food. Although much modified in structure, the tuber contains all the usual stem parts—bark, wood, pith, nodes, and internodes.
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 of the dahlia and the potato, and the rhizomerhizome
or rootstock,
fleshy, creeping underground stem by means of which certain plants propagate themselves. Buds that form at the joints produce new shoots.
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 of certain irises. All such organs are specialized subterranean stems serving for food and water storage and asexual reproduction.


See J. E. Bryan, Bulbs (1989).



a modified, usually subterranean shoot with a greatly shortened stem and fleshy scalelike leaves.

Bulbs store water and nutritive substances (primarily sugars); they are also a means of vegetative renewal and reproduction. In some plant species, bulblets develop in the inflorescences (onions and meadow grasses) or in the leaf axils of aboveground shoots (lilies and toothworts). Bulbs can function as storage organs for approximately one year (annual bulbs of tulips, onions, and fritillary) or longer (perennial bulbs of narcissus, snowdrop, and hyacinth). After their nutrients have been used, dry scales form protective outer coverings. Scaly bulbs have narrow scales that touch the bulb only at their bases (lilies); tunicated bulbs have broad enwrapping scales (onions).

According to the manner of growth, two types of bulbs are distinguished. Monopodial, or intermediate, bulbs renew themselves at the expense of the terminal bud of the bulb stem (snow-drop, narcissus, and belladonna lily). In plants with sympodial, or determinate, bulbs, the inflorescence and aboveground parts develop from the terminal bud, but the bulb regenerates at the expense of the bud located in the axil of a scale (tulips, onions, and hyacinths). In sympodial bulbs the mother bulb is replaced annually by daughter bulbs. If not one but two or more buds are active, the bulb reproduces vegetatively. In garlic plants several cloves form in the axils of the bulb scales and are arranged in a row, thus constituting complex bulbs.



A short, subterranean stem with many overlapping fleshy leaf bases or scales, such as in the onion and tulip.


In lighting, see lamp bulb, light bulb.


1. a rounded organ of vegetative reproduction in plants such as the tulip and onion: a flattened stem bearing a central shoot surrounded by fleshy nutritive inner leaves and thin brown outer leaves
2. a plant, such as a hyacinth or daffodil, that grows from a bulb
3. See light bulb
4. a rounded part of an instrument such as a syringe or thermometer
5. Anatomy a rounded expansion of a cylindrical organ or part, such as the medulla oblongata
6. Nautical a bulbous protuberance at the forefoot of a ship to reduce turbulence
References in periodicals archive ?
Iris yellow spot virus: An emerging threat to onion bulb and seed production.
to abridge the gape of poverty through introducing the most promising and economically feasible intervention like maintenance of recommended plant population of certified onion bulb seed, one of the effective and possibly successful agriculture venture considered as a case study in Malakand Division.
Scallions, or green onions, are simply immature yellow onion bulbs.
Utilizing powerful ingredients like Aquacacteen, onion bulb extract, lysine and Benzoyl Peroxide, CoverAid goes to work fast to keep skin looking fresh and feeling great.
WRITE the name of the one you love on the base of an onion bulb.
Photo: Onion bulb consists of concentricshells of leaf bases swollen with stored water and sugars.
The onion bulbs are generally stored from May to November for a period of four to six months.
Onion bulbs have numerous organic sulphur compounds, flavonoids and phenolic acids with proven antibacterial, antioxidant and hypolipidemic efficacy (Melvin Joe et al.
Lot 04 Supply and delivery of onion bulbs and other flowers Minimum total 16 000 EUR HT maximum overall amount 64 000 EUR excluding VAT.
The use of onion bulbs and other parts of the plant for therapeutic purposes has been reported in traditional medicines of a number of countries.
2 artichoke hearts, blanched in acidulated water, drained 2 baby zucchini, 1 shaved into thin slices on mandoline, 1 cut into bite-size pieces 2 summer squash, 1 shaved into thin slices on mandoline, 1 cut into bite-size pieces 2 round radishes, trimmed, thinly sliced 2 purple spring onion bulbs, trimmed, peeled, quartered, cut into bite-size pieces 4 cooked discs put pastry 4 inches in diameter, perforated with 5 holes toward center Petals of 2 squash blossoms 20 thin slices black truffle Olive oil to taste Fleur de sel and freshly ground black and white peppers to taste * Substilule seasonal vegetable, greens and/or roots as needed, raw almonds may be added as well
3 more ways wilt chopped onion bulbs in oil with morel mushrooms.