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B. r. subsp. narinosa
|Brassica rapa subsp. narinosa|
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Tatsoi (Brassica rapa subsp. narinosa or Brassica rapa var. rosularis) is an Asian variety of Brassica rapa grown for greens. Also called tat choy, it is closely related to the more familiar Bok Choy. This plant has become popular in North American cuisine as well, and is now grown throughout the world.
The name comes from Cantonese 塌菜 taap3 coi3 or "drooping vegetable", often rendered 'tat soi', 'tat choy'. However, its natural habitat is alongside the Yangtze River, where it is called 塌棵菜 (Shanghai and around Lake Tai, Wu thaq-khu tshe), 烏塌菜 (Lake Tai and Nanking, Wu wu-thaq tshe, literally "dark drooping veggie"). Mandarin borrowed the name 塌棵菜 (Pinyin tā kē cài). It is also called 'Chinese flat cabbage', 'rosette pakchoi' or 'broadbeaked mustard', 'spoon mustard', or 'spinach mustard'.
The plant has dark green spoon-shaped leaves which form a thick rosette. It has a soft creamy texture and has a subtle yet distinctive flavour.
It can be grown to harvestable size in 45–50 days, and can withstand temperatures down to –10 °C (15 °F). Tatsoi can even be harvested from under snow.
- Days to Maturity: 45
- When to Sow
- Outside: As early as the soil can be worked. Sow again in late summer or fall.
- Inside: Sow directly outdoors.
- Seed Depth: 1/4" to 1/2"
- Seed Spacing: 6"
- Row Spacing: 18"
- Days to Emerge: 5 - 15
- Thinning: When 4" tall, thin to 6" apart.
Tatsoi is used for pesto, salads, stir frys and garnishing soup. According to Food52, "Tatsoi is a very versatile green, equally suited to being served raw or lightly cooked. To make it easy, just use tatsoi anywhere you’d use spinach. Lightly steam or sauté it, wilt the leaves with a warm dressing, or add them to a soup at the end of cooking."
The leaves are similar to romaine, while the stalks taste a little like cucumber, with a mild bitterness. Leaves and inner stalk are tender; outer stalk is typically discarded. Typical cooking is to stir fry the leaves and the stalks. They also can be pickled. 
- Report of a Vegetables Network: Joint Meeting with an Ad Hoc Group on Leafy Vegetables, 22-24 May 2003, Skierniewice, Poland. Rome: Bioversity International. 2005. p. 58. ISBN 9789290436799. Retrieved 16 March 2016.
- Creasy, Rosalind (15 Mar 1999). The Edible Salad Garden. Vermont: Tuttle Publishing. p. 48. ISBN 9781462917617. Retrieved 16 March 2016.
- "Sorting Brassica rapa names". Multilingual Multiscript Plant Name Database. The University of Melbourne. Retrieved 17 March 2016.
- "Nutrition Facts for Tatsoi (Spoon Mustard)". HealWithFood.org. Retrieved 17 March 2016.
- Hard, Lindsay-Jean, "Tatsoi Is the New Spinach (Haven't You Heard?)", Food52, January 28, 2020. Retrieved July 25,2020.
- Jay, Ben, "The Serious Eats Field Guide to Asian Greens", Serious Eats, May 15, 2014. Retrieved July 25,2020.