# Choy sum

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{{Short description|Leafy vegetable}}
{{redirect|Cai xin|the Chinese media group|Caixin}}
{{Infobox Cultivar
| name          = Choy sum <small>(Cantonese)</small><br />Cai xin <small>(Mandarin)</small>
| image         = Choi Sum stalks.JPG
| image_caption = Choy sum plants, growing on a farm
| species       = ''[Brassica rapa](/source/Brassica_rapa)'' var. ''parachinensis''
| group         = Chinensis, Pekinensis groups
| origin        = [China](/source/China), before the 15th century
| subdivision   = Many; see text.
}}
{{Infobox Chinese
| title    = Choy sum (cai xin)
| c        = 菜心
| p        = càixīn
| mi       = {{IPAc-cmn|c|ai|4|.|x|in|1}}
| j        = coi<sup>3</sup>sam<sup>1</sup>
| ci       = {{IPA|yue|tsʰɔ̄ːy sɐ́m|}}
| poj      = chhài-sim or<br />tshài-sim
| showflag = pj
}}

'''Choy sum''' (also spelled '''choi sum''' or '''choi sam''' in [Cantonese](/source/Cantonese); '''caixin''' ({{zh|c=菜心|p= ''càixīn''}}) in [Standard Mandarin](/source/Standard_Chinese)) is a leafy vegetable commonly used in [Chinese cuisine](/source/Chinese_cuisine). It is a member of the genus ''[Brassica](/source/Brassica)'' of the mustard family, [Brassicaceae](/source/Brassicaceae) (''[Brassica rapa](/source/Brassica_rapa)'' var. ''parachinensis'' or ''[Brassica chinensis](/source/Brassica_chinensis)'' var. ''parachinensis''). Choy sum is a transliteration of the Cantonese name ({{zh|c=菜心}}), which can be literally translated as "heart of the vegetable". Choy sum is also called '''yu choy''' ('''you cai''' in Standard Mandarin; Chinese: 油菜). It is also known as '''Chinese flowering cabbage'''.<ref>{{cite web|url=http://www.spsnz.com/our-products/asian-vegetables/choy-sum/choy-sum.html |title=CHOY SUM &#124; South Pacific Seeds |access-date=2013-04-18 |url-status = dead|archive-url=https://web.archive.org/web/20130208152820/http://www.spsnz.com/our-products/asian-vegetables/choy-sum/choy-sum.html |archive-date=2013-02-08 }}</ref>

==Description==
Choy sum is a green leafy vegetable similar to [gai lan](/source/gai_lan), and can be characterized by the distinct yellow flowers which it bears. Each flower has four yellow, oval to round [petal](/source/petal)s with six stamens on fleshy, erect stems which are {{convert| 0.5|to|1|cm|in|frac=4|abbr=off}} in diameter and {{convert|15|to|20|cm|in|frac=2|abbr=on}} tall with light to dark green, and are oval (becomes [acuminate](/source/Leaf_shape) shaped, or basal-shaped near the flowering stage) with slightly serrated margins leaves, which never forms compact heads like the cabbage. Fruits can develop out of cross-pollination or self-pollination, and are [silique](/source/silique) structured, that open at maturity through [dehiscence](/source/Dehiscence_(botany)) or drying to bare open to brown or black seeds that are small and round in shape. A single pod can bear 4 to 46 seeds.

The height of the plant varies greatly, ranging from {{convert|10|to|40|cm|in|0|abbr=on}} depending on the growing conditions and the variety. Flowering usually appears when there are about 7 to 8 leaves on the plant or about {{convert|20|cm|in|frac=2|abbr=on}} tall. The bulk of the root system is found within a depth of {{convert|12|cm|in|frac=2|abbr=on}} and is confined to a radius of {{convert|12|cm|in|frac=2|abbr=on}}.<ref>{{cite web|url=http://www.dpi.vic.gov.au/agriculture/horticulture/vegetables/vegetables-a-z/chinese-flowering-cabbage-choy-sum|title=Agriculture|first=Department of Economic Development, Jobs, Transport and|last=Resources|website=www.dpi.vic.gov.au|date=2017-05-22}}</ref><ref>{{cite web |url=http://www.cqu.edu.au/research/research-organisations/institutes/resource-industries-and-sustainability/centres2/centre-for-plant-and-water-science/research-oxygation,-stevia,-waste-water,-phytoremediation-and-non-invasive-assessment/asian-vegetables/chinese-flowering-cabbage |title=CQUniversity Australia - Chinese Flowering Cabbage |access-date=2013-02-17 |url-status = dead|archive-url=https://web.archive.org/web/20130226012451/http://www.cqu.edu.au/research/research-organisations/institutes/resource-industries-and-sustainability/centres2/centre-for-plant-and-water-science/research-oxygation%2C-stevia%2C-waste-water%2C-phytoremediation-and-non-invasive-assessment/asian-vegetables/chinese-flowering-cabbage |archive-date=2013-02-26 }}</ref>

The whole plant is overall an [annual](/source/Annual_plant), [herbaceous](/source/Herbaceous_plant) plant, rarely [perennial](/source/Perennial_plant), rarely growing into subshrubs. The whole plant consists of a simple or branched (when it is near the flowering stage), leafy structure. It grows best in soil with a minimum [pH](/source/pH) level of 5.6, maximum pH level of 7.5.<ref>{{cite web |url=http://zipcodezoo.com/Plants/B/Brassica_chinensis_var__parachinensis/ |title=Brassica chinensis var. Parachinensis (Choy Sum) |website=zipcodezoo.com |access-date=22 May 2022 |archive-url=https://archive.today/20130412063007/http://zipcodezoo.com/Plants/B/Brassica_chinensis_var__parachinensis/ |archive-date=12 April 2013 |url-status=dead}}</ref>

== Use == 
Choy sum is highly valued as a vegetable in China and Japan. It is commonly consumed in soup, blanched, or stir-fried.<ref name= "Cook's Guide" >{{cite book |last1=Hutton |first1=Wendy |title=A Cook's Guide to Asian Vegetables |date=2004 |publisher=Periplus Editions |location=Singapore |isbn=0794600786 |pages=44–45}}</ref>

==Gallery==
<gallery caption="" widths="220px" heights="120px">
Chinese vegetable 027.jpg|Typical choy sum fresh from field in [Hainan](/source/Hainan)
Phak kwangtung905.JPG|Choy sum variety in [Thailand](/source/Thailand), called phàk Kwangtûng (lit: [Cantonese](/source/Cantonese) cabbage; cabbage of [Guangdong](/source/Guangdong))
Purple Choi Sum stalks besides ruler.JPG|Purple choi sum, a choy sum variety in Hong Kong
Choy Sum with Soy Sauce.jpg|Cooked choy sum in soy sauce in Hong Kong
</gallery>

== See also ==
* [List of leaf vegetables](/source/List_of_leaf_vegetables)
* [Bok choy](/source/Bok_choy)

==References==
{{Commons category|Brassica rapa subsp. chinensis var. parachinensis}}
{{Reflist}}

{{Brassica}}

Category:Brassica
Category:Cantonese cuisine
Category:East Asian vegetables
Category:Leaf vegetables

{{China-cuisine-stub}}
{{vegetable-stub}}

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Adapted from the Wikipedia article [Choy sum](https://en.wikipedia.org/wiki/Choy_sum) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Choy_sum?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.