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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 ?
Besides the flower bulb mosaic, the Golden Age also forms an inspiration for the numerous flower shows in the Oranje Nassau Pavilion.
With its 32 hectares containing 7 million flower bulbs planted by hand in more than 1,600 different varieties, the Keukenhof is the largest bulb flower park in the world.
In addition to the competition, Armitage's Birchencliffe Garden Centre will host a fabulous bulb planting workshop where experts from the Eden Project and the Netherlands Flower Bulb Information Centre will share their hints and tips for getting the very best out of bulbs.
The Netherlands Flower Bulb Information Centre recommends three simple steps for planting summer bulbs:
Life on a faraway planet in the Ooni Kingdom is surreal, where the Kirki village people grow their computers from CPU seeds, walk around with small mirrors sewn into their clothing (appearance is a big deal in the Ooni Kingdom) and flower bulbs are used as candlelight.
Photo courtesy of Netherlands Flower Bulb Information Center
At the annual 'Best of the best' flower bulb ceremony in The Netherlands, gardeners voted the Dahlia Arabian Night the must-plant summer flower bulb, ahead of cannas, oxalis and zantedeschia.
A Meridian flower bulb company with Holland roots has blossomed into a successful international business thanks to careful cultivation by its two owners, who are carrying on a family tradition that began in 1919.
Flower expert Lucas Boreel, from the Netherlands Flower Bulb Information Centre, says: 'Combine colours and materials that contrast liveliness with a natural crudeness - such as floral tin cups and old patterned jugs.
FOR more information on bulbs contact the Netherlands Flower Bulb Information Centre (020 7915 4776 www.
Frans, technical director of the Netherlands Flower Bulb Information Service, is clearly a dessert man.
The best time to plant tulips and daffodils is in the fall, according to the Netherlands Flower Bulb Information Center.