|Asparagus officinalis subsp. var.||Asparagus|
Asparagus officinalis is a spring vegetable. A flowering perennial  plant species in the genus Asparagus in the lily family, like its allium cousins, onions and garlic, it is native to most of Europe, northern Africa and western Asia. and is widely cultivated as a vegetable crop.
Asparagus is a herbaceous perennial plant growing to 100 - 150 cm tall, with stout larissa stems with much-branched feathery foliage. The "leaves" are in fact needle-like cladodes (modified stems) in the axils of scale leaves; they are 6 – 32 mm long and 1 mm broad, and clustered 4–15 together. The root system is adventitious and the root type is fasciculated. The flowers are bell-shaped, greenish-white to yellowish, 4.5 – 6.5 mm long, with six tepals partially fused together at the base; they are produced singly or in clusters of 2–3 in the junctions of the branchlets. It is usually dioecious, with male and female flowers on separate plants, but sometimes hermaphrodite flowers are found. The fruit is a small red berry 6–10 mm diameter, which is poisonous to humans.
Plants native to the western coasts of Europe (from northern Spain north to Ireland, Great Britain, and northwest Germany) are treated as Asparagus officinalis subsp. prostratus (Dumort.) Corb., distinguished by its low-growing, often prostrate stems growing to only 30 – 70 cm high, and shorter cladodes 2 – 18 mm long. It is treated as a distinct species Asparagus prostratus Dumort by some authors.
In northwestern Europe, the season for asparagus production is short, traditionally beginning on April 23 and ending on Midsummer Day.
Template:See also Since asparagus often originates in maritime habitats, it thrives in soils that are too saline for normal weeds to grow in. Thus a little salt was traditionally used to suppress weeds in beds intended for asparagus; this has the disadvantage that the soil cannot be used for anything else. Some places are better for growing asparagus than others. The fertility of the soil is a large factor. "Crowns" are planted in winter, and the first shoots appear in spring; the first pickings or "thinnings" are known as sprue asparagus. Sprue have thin stems.
White asparagus, known as spargel, is cultivated by denying the plants light while they are being grown. Less bitter than the green variety, it is very popular in the Netherlands, France, Belgium and Germany where 57,000 tonnes (61% of consumer demands) are produced annually.
Asparagus is a useful companion plant for tomatoes. The tomato plant repels the asparagus beetle, as do several other common companion plants of tomatoes, meanwhile asparagus may repel some harmful root nematodes that affect tomato plants.
Pests and diseases
Purple asparagus differs from its green and white counterparts, having high sugar and low fibre levels. Purple asparagus was originally developed in Italy and commercialised under the variety name Violetto d'Albenga. Since then, breeding work has continued in countries such as the United States and New Zealand.Template:Verify source
- ↑ Grubben, G.J.H.; Denton, O.A., eds (2004). Plant Resources of Tropical Africa 2. Vegetables. PROTA Foundation, Wageningen; Backhuys, Leiden; CTA, Wageningen.
- ↑ 2.0 2.1 "Asparagus officinalis". Flora Europaea. Royal Botanic Garden Edinburgh. Retrieved on 2010-05-19.
- ↑ "Asparagus officinalis". Euro+Med Plantbase Project. Botanic Garden and Botanical Museum Berlin-Dahlem. Retrieved on 2010-05-19.
- ↑ USDA, ARS, National Genetic Resources Program. "Asparagus officinalis". Germplasm Resources Information Network. Beltsville, Maryland: National Germplasm Resources Laboratory. Retrieved on 2010-05-19.
- ↑ http://www.gardengrow.co.nz/plant/Asparagus
- ↑ Cite error: Invalid
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- ↑ "Asparagus prostratus (Asparagus, Wild)". Interactive Flora of NW Europe. ETI BioInformatics. Retrieved on 2010-05-19.
- ↑ USDA, ARS, National Genetic Resources Program. "Asparagus prostratus". Germplasm Resources Information Network. Beltsville, Maryland: National Germplasm Resources Laboratory. Retrieved on 2010-05-19.
- ↑ Oxford Times: "Time to glory in asparagus again".
- ↑ "BBC – Food – Glossary – 'S'". BBC Online. Retrieved on 2007-06-08.
- ↑ Molly Spence. "Asparagus: The King of Vegetables" (DOC). German Agricultural Marketing Board. Retrieved on 2007-02-26.
- ↑ http://www.ibiblio.org/pfaf/cgi-bin/arr_html?Asparagus+officinalis
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