Sub-species
Plants in this species are divided into several groups depending on their distinct characteristics and include; Narinosa, Chinensis, Perviridis, Pekinensis, Rapifera and Ruvo group.

Chinensis Group
This group includes; Bok Choi, Pak Choi, Chinese celery cabbage and Japanese cabbage.

subsp. chinensis
Bok Choi, Pak Choi
This plant is an annual or rarely a biennial with dark green basal leaves that do not form a compact head. There are many variations that include Bok Choy 'White vegetable' which has whitish petioles and crinkly dark green leaf blades. There are over 20-varieations of this plant and include baby Bok Choy which is commonly cooked whole and another is Bok Choi sum and in this case the leaves are trimmed off and the stalks (petiole) is eaten.

Pak Choy may also be called Bok Choi but is commonly recognised as the green stem variety which has broad flat green stems (petiole) and oblong to rounded light green leaf blades in outline and are harvested when they reach a height of 150 mm (6 in) tall. This cool season vegetable is harder than other varieties tolerating light frost, heat and cold conditions and is normally grown during spring and autumn requiring ample light. It is also sensitive to acidic soils preferring neutral conditions around a pH of 7.0.

Under cultivation Pak Choi and Bok Choi are shallow rooted plants that require frequent watering but not leaching of the soil. The use of film covers around the plants during cooler months and light shade cloth over the plants during mid summer is advisable. 

Excessive nitrogen fertiliser and moisture is not advisable as it encourages bacterial soft rot. When planting out in rows space the plants 100 mm (2 in) apart for the small varieties and 450 mm (18 in) apart for larger varieties and the rows should be around 300 mm (1 ft) apart. They are normally harvested during the cooler part of the day by hand from the base, 35 to 55 days from sowing when the leaves are fresh and crisp, not yellow.

The tiny seeds can be sown in flats than pricked out and transplanted into the prepared bed after 20 days or sown directly into a well aerated raised garden bed ensuring that they are not deeper that 20 mm (¾ in).

Narinosa Group
Plants in this group are commonly known as tatsoi (tat soi) or flat Pac Cho. It is a cool season biennial that forms a compact flat cluster (rosette) of a broad spoon-shaped (spathulate) leaves with thick leaf stalks (petiole). It is a fast growing and matures in 21 days for baby greens or 45 days for mature heads. 

If allowed to flower (bolt) it produces upright clusters of bright yellow flowers from spring to summer in the second year of growth. The leaves of tatsoi are tasty and nutritious and can be picked when young and used in salads or mature leaves are used in stir fry. It is normally cultivated from spring to summer or autumn to winter in an open sunny position and grows in well-drained moderately fertile neutral to slightly acid soil and is drought tender but frost tolerant.

Pekinensis Group
subsp. pekinensis
NAPA Cabbage, Wombok, Hakusia
There are several varieties of Chinese cabbage and the most common is the NAPA cabbage (sui choy) that has upright broad green leaves with white stems (petioles) and form a compact cylindrical head of pale green foliage and is rich in vitamin C. There are over 12 varieties of the NAPA cabbage these include;

Hybrid Super
This hybrid is a slow bolting and forms a barrel shaped head of light green leaves up to 2kg (6 lb) and is normally cultivated in spring or autumn.

Hybrid Spring Delight
This small variety produces an early spring summer crop with dark green leaves and tender well flavoured yellow inner leaves and grows in semi shade with low temperatures.  It produces a tightly packed head that is up to 114 g (.25 lb)

'Hybrid Kingdom 80'
This large hybrid is a slow bolting and forms a barrel shaped head of light green leaves up to 4kg (11 lb). It takes up to 80 days to mature is normally cultivated from a late summer to autumn. It is commonly cultivated in home gardens and is resistant to disease.

'Hybrid Yellow King'
This hybrid forms head up to 2kg (6 lb) of overlapping dark green leaves with bright yellow inner leaves and is harvested 66 days after sowing. It is suitable for early spring or autumn crops preferring slightly cooler weather.

'Hybrid Hwa King'
This commonly grown hybrid forms a barrel shaped head of bright green leaves that is up to 2kg (6 lb). It is suitable for early spring or autumn crops preferring slightly cooler weather.

'Wong Bok'
This commonly grown variety forms a compact barrel shaped head of dark green leaves and weighs up to 4kg (10 lb). It is suitable for autumn / winter crops preferring cooler weather.

'Hybrid Tropic Pioneer'
This hybrid has been developed to grow in subtropical or tropical regions and forms a compact barrel shaped head of tender, tasty mid green leaves.

Tendergreen and Mustard spinach is also included in that Pekinensis Group.
Plants in this group are biennial and are grown for their large glossy spathulate leaves or their swollen roots.  They grow to a height of 500 mm (20 in) rapidly and tend to bolt (flower) during warmer weather. They are grown for their tender leaves that can be eaten raw or cooked and have a cabbage or mustard flavour and can be picked from seedling stage to mature plants where the flavour becomes hotter. 

There are many varieties available and are cool season vegetables that prefer a sunny to semi-shaded position and mature in 55 to 80 days. They grow a in well-drained moderately fertile sandy to heavy soil at the that neutral tending acidic and is slightly drought and light frost tolerant.

Rapifera Group
Turnips
This group includes turnips which grow to 457 mm (18 in) tall and have a swollen tap root that is very variable in shape, size and colour and are round or cylindrical. The colour varies from yellow to white and may be green, red or purple towards the top. The size also varies from small to very large up to 22 kg (50 lb) and the larger the turnip that more pungent it becomes. The lush green foliage is also edible and the plant is commonly cultivated in temperate regions worldwide but originated from Europe to the Middle East.

Sow fresh seeds 12 mm (½ in) deep and 100 mm 4 in) apart in rows during early spring or during midsummer in an open sunny position.  They prefer a well-drained but moist moderately fertile friable soil that is a neutral tending acidic and are light frost and drought tolerant.  No Turnips are normally harvested when a young and tend to have a stronger flavour during drier conditions.

Ruvo Group
Italian Turnip, Broccoli Raab
Broccoli Raab is also known as Rapa, Rabe or Rapin and a characterised by there tall violin-shaped shaped dark green leaves with a long petiole and form an open cluster.  They produce clusters of edible broccoli-like flower buds that have a pungent flavour and commonly used in salads or are cooked.  There are many varieties available including;

'Marzatica Broccoli'
This late-season biennial produces robust florets during early winter that taste similar to standard broccoli with a slightly mustard flavour.