Asian Greens

Start from seed: January-April and July-December

Optimum soil temperature for germination: 10-30°C

Plant seedlings: All year except for May and June

Plant spacing: 15-30 cm

Days to maturity: 30-60 days

Introduction

Asian greens include a diverse group of leafy green and red/purple vegetables originating from East and Southeast Asia, such as bok choi, Pak choi, tatsoi, mizuna, mustard greens, Gai lan (Chinese broccoli) and komatsuna. These vegetables belong to the Brassicaceae family which includes broccoli, cauliflower, kale, kohl rabi, Brussels sprouts, turnips, radish, rocket and collards.

Asian greens have been cultivated in Asia for thousands of years and have become increasingly popular worldwide due to their quick growth, nutritional value, and culinary versatility. They’re packed with vitamins A, C, and K, as well as calcium and iron.

These vegetables generally have tender leaves and stems that can be eaten raw in salads or cooked in stir-fries, soups, and other dishes. Many varieties are fast-growing and can be harvested young as baby greens or allowed to mature into full-sized plants.

Site and soil

Asian greens grow well in Canberra’s climate, particularly in spring and autumn. They prefer full sun during cooler months but benefit from partial shade during warmer weather to prevent bolting.

Ensure the soil is prepared using compost, aged manure and a complete organic fertiliser. Asian greens thrive in fertile, well-drained soil with a pH of 6.0-7.5. It is commonly thought that they prefer alkaline soil. This is because clubroot disease can be problematic for Brassicas in acidic soils. If this is the case liming to raise the pH above 7.0, ideally to 7.8, is beneficial.

For container growing, use a premium potting mix with added organic fertilizer. Containers should be at least 15-20 cm deep with good drainage.

For details on preparing soil and pots, including the use of lime, dolomite, gypsum and fertilizers, please refer to the COGS guide to garden bed preparation.

Planting Seeds and Seedlings

Asian greens can be direct-sown or grown as seedlings.

When direct-sowing, plant seeds twice the depth of the size of the seed in rows 25cm apart. Thin seedlings to 15-30 cm apart depending on the variety—compact varieties like tatsoi need less space than larger varieties like bok choy. Mizuna and mustard greens can be planted even closer together.

For seedling production, sow in cell trays, or similar, filled with seed-raising mix. Seedlings typically emerge in 4-10 days and are ready for transplanting when they have 3-4 true leaves, usually 3-4 weeks after sowing.

After planting, water with a seaweed solution and apply organic mulch to retain moisture and suppress weeds.

Cultivation

In Canberra, plant Asian greens all year round except for in May and June when daylight hours fall below 10 hours per day. Although most Asian greens are frost tolerant, caterpillar tunnels cloaked in horticultural plastic can be erected over seedlings to protect plants from frost and extend the growing season.

A seaweed solution applied fortnightly can help boost plant resilience and overall health. Alternatively, a monthly foliar spray with seaweed solution; a mix of worm juice, seaweed and compost tea; or trace elements will help boost growth and resilience to pests and diseases.

Asian greens need consistent moisture to grow well and prevent bitterness. Water regularly, keeping the soil evenly moist but not waterlogged. During hot periods, water more frequently.

Keep the growing area weed-free, especially when plants are young. Apply organic mulch to suppress weeds and retain soil moisture.

The trickiest time to grow leafy greens in Canberra is in Spring when the daylength increases rapidly, triggering plants to flower, known as bolting. This can be somewhat avoided by frequent planting (succession planting) and harvesting the leaves when they are young. Some Asian greens can also bolt quickly in hot weather or if water stressed.

Harvesting

Most Asian greens can be harvested in stages. Baby leaves can be harvested as early as 3-4 weeks after sowing, while mature plants typically take 30-60 days depending on the variety.

For leafy varieties like mizuna or tatsoi, you can harvest outer leaves continuously as needed, allowing the centre to continue growing. For heading varieties like bok choy, harvest the entire plant by cutting at the base when it reaches maturity.

Morning is the best time to harvest for the crispest, sweetest leaves. Leaves harvested in the heat of the day often taste bitter. Use immediately for best flavour or refrigerate for up to a week.

Problems

Asian greens face similar pest and disease challenges as other brassicas. The best approach is to have a reliable Australian reference book to identify problems. Garden Pests, Disease and Good Bugs by Denis Crawford is recommended.

A general strategy to follow with any problem is to observe the plant carefully before taking action. Identify the problem then carefully consider the course of action. For example, with pest insects, you often can see a predator nearby. If you watch and wait the predator may deal with the problem for you. Beneficial predatory insects which feed on pest insects can be purchased from suppliers such as Bugs for Bugs. If the problem needs further action the above recommended book has suggestions.

Practicing good garden hygiene, crop rotation, and maintaining plant vigour by providing adequate nutrients are key strategies for prevention.

Cabbage White Butterfly (Pieris rapae): This common pest lays tiny white eggs on the undersides of leaves. The green caterpillars that hatch are perfectly camouflaged and feed on leaves, creating irregular holes and contaminating plants with their droppings. Exclusion netting is the most reliable method to prevent damage from cabbage white butterfly. Keep in mind that the netting also excludes beneficial insects and birds that glean plants cleaning up other pests. Thus, leaving the netting on for too long can result in populations of sap suckers such as aphids, thrips and white fly building up inside the netting.

Control methods include:

Covering plants with fine insect mesh or exclusion netting from the time of planting
Regularly inspecting and manually removing eggs and caterpillars
Using biological controls such as Bacillus thuringiensis (also known as Bt and sold as Dipel) for significant infestations
Creating butterfly decoys by placing white plastic pieces around plants
Avoiding brassica weeds that act as hosts

Clubroot (Plasmodiophora brassicae): This soil-borne disease causes swollen, deformed roots and stunted growth. Plants may wilt during warm weather and show yellowing leaves. The disease thrives in acidic soils (below pH 7.0) and can persist in soil for many years. Management includes:

Maintaining soil pH above 7.0, ideally 7.8, through liming
Practicing crop rotation (avoid planting brassicas in the same area for at least 4 years)
Improving drainage in wet areas
Removing and disposing of infected plants (do not compost)
Using disease-free transplants and clean tools

Aphids, thrips and white fly: These small sap-sucking insects can transmit celery mosaic virus. They often cluster on the undersides of leaves, causing distortion and stunting. Small populations can be controlled by washing them off with a strong stream of water or using insecticidal soap. Alternatively, neem oil or pyrethrin can be used. Beneficial predators like ladybugs and lacewings should be encouraged and can be purchased for release on the crop. Look for aphid mummies which are evidence that the aphid has been parasitised. Eggs can also be parasitised and will appear bronze in colour. Generally speaking, plants that are high in soluble nitrogen (nitrates and ammonia) are prone to attack by sap sucking insects. Ideally avoid using soluble nitrogen fertilisers and ensure plants have adequate trace elements. This can be achieved by using foliar sprays.

Recommended Varieties

The following Asian green varieties perform well in Canberra’s climate.

Pak Choi/Bok Choy:

Baby Bok Choy – compact plants ideal for small spaces
White Stem – classic variety with crisp white stems
Shanghai Green – heat tolerant with glossy leaves
Joi Choi – green Pak choi
Rosie – red Pak choi

Tatsoi: baby leaves can be eaten when 21 days old or left to grow into a rosette and harvested whole

Tatsoi – spoon-shaped dark green leaves
Purple Tatsoi, Viola and Purple Heart – attractive purple leaves

Mizuna: feathery leaves growing in an attractive clump. Green, purple and variegated.

Mizuna – finely serrated leaves with mild flavour. Red and Lime green streaks is a nice variegated variety of mizuna. Red deer is another variegated variety.
Purple Mizuna, Miztique, Ruby Streaks– reddish-purple leaves with mild to strong mustard flavour

Other Asian Greens:

Komatsuna (Japanese mustard spinach) – heat tolerant with mild flavour
Mibuna – narrow, strap-like leaves with mild flavour
Gai Lan, Lai (Chinese broccoli) – thicker stems and blue-green leaves
Red Giant – beautiful, strongly flavoured, large purple leaves.
Tokyo Bekana – non heading Chinese cabbage with buttery leaves and crisp mid rib.

References

Bubel, Nancy. The New Seed-Starters Handbook. Rodale Books, 2018.
Crawford D. Garden Pests, Disease and Good Bugs. Australia: ABC Books; 2015.
Department of Primary Industries and Regional Development. (n.d.). Managing clubroot in vegetable brassica crops. https://www.agric.wa.gov.au/broccoli/managing-clubroot-vegetable-brassica-crops
Dove, Helena. Botany of the Kitchen Garden, Kew Publishing, Royal Botanic Gardens Kew, UK, 2023.
Gardenate. (2024). Growing Cabbage in Australia – temperate climate. https://www.gardenate.com/plant/Cabbage?zone=2
Johnny’s Selected Seeds. (2022). Growing Cabbage From Seed. https://www.johnnyseeds.com/growers-library/vegetables/cabbage/cabbage-key-growing-information.html
The Seed Collection. (n.d.). Cabbage seeds. https://www.theseedcollection.com.au/vegetable/cabbage
Yates Australia. (2024). How to Grow Cabbage. https://www.yates.com.au/how-to-grow/cabbage/