History and profile
Pak Choi (sometimes known as Bok Choy) – Brassica rapa Var. chinensis has been grown in Southern China since at least the 5th century AD. It is a fast growing biennial, but will usually go to seed in the first season if sown in unfavourable conditions. Pak chois vary in size from 10 to 50 cm high. They are shallow rooted and fast growing and the younger the plant the tenderer they are.
Site and soil
Since it is so shallow rooted Pak Choi needs to be grown in fertile, moisture retentive ground. They should not be allowed to dry out at any stage. Most of the varieties widely available are cool season crops and do best in sunny, open positions with temperatures in the range 15-20C.
Pak Choi can be grown as a seedling, cut-and-come-again crop for small salad leaves, or be allowed to grow into full sized plants, or grown even longer for the flowering shoots
If Pak Choi is grown as a seedling crop it can be sown thickly in rows under cover in Spring – Summer sowings will probably bolt.
For mature plants sow in modules from mid-Summer to Autumn and plant out when weather is cool and preferably the soil is very moist.
For overwintering under cover sow in modules late August to mid September.
I suggest sowing in modules as disturbance when transplanting is one of the main triggers of premature bolting.
Spacing depends on the size of plants wanted. 15-20cm is sufficient for small plants, For large plants, especially if being left for flowering shoots in Spring 30-40cm is probably better. Very small varieties can be planted at as little as 10cm apart.
Pak Chois are greedy and thirsty plants and care must be taken to ensure they do not dry out – water little and frequently.
If grown in Autumn and over Winter the main problem is likely to be slugs and snails. If you have clubroot, pak choi will fail as it succumbs much more quickly that Western brassicas.
Seedling crops raw in salads
Mature plants and flowering shoots steamed or stir-fried
Joi Choi (F1) – large plants, slow to bolt – white stems
Ivory (F1) – large upright plants – white stems
Mei Qing Choi (F1) – medium size – green stems
Canton Dwarf – the smallest of all – white stems
Other oriental brassicas to grow similarly
Chinese cabbage, Tatsoi, Choi sum (for flowing heads), Japanese mustards including Komatsuna, Red Mustard, Mizuna, Mibuna.
For more discussion on Pak Choi see:-