How to Grow Chinese Broccoli in Australia

Chinese broccoli, or kai lan (Brassica oleracea Alboglabra Group), is a cabbage-family (Brassicaceae) crop grown for its thick stems, leaves and white-flowered shoots. Also called gai lan, it copes with warmer weather than broccoli, its close relative, so every Australian zone has a window for it. The usual mistake is waiting for a broccoli-sized head.

Three mistakes that matter

1. Waiting for the flowers. Once the white flowers open, the stems turn woody and the plant puts its effort into seed. Cut each shoot while the buds are formed but still closed.
2. Rushing seedlings in warm weather. Seedlings that race along in trays in warm weather often flower while still small, giving few leaves and thin stems. Sow inside your zone's window and plant out at three to four weeks, before roots crowd the cell.
3. Leaving plants uncovered. Caterpillars of cabbage white butterfly (Pieris rapae) and diamondback moth (Plutella xylostella) chew the leaves and can tunnel into the shoots. Stretch fine insect mesh over hoops on sowing or planting day.

When to plant

Seed germinates in soil from about 7°C to 30°C, fastest at 25°C to 30°C, and plants grow best in air between 18°C and 28°C. Cold spells push young plants to flower early, so in most zones the strongest crops come from sowings in late summer and autumn. Sow a fresh row each time the last one reaches about half size, for a steady supply.

At the hot end of a window, stretch shadecloth over the row and water more often. In the temperate and Mediterranean zones, autumn rows sown before Anzac Day usually crop before winter slows them. Plants take light frost but not a hard freeze.

Site, soil and setup

Give Chinese broccoli a sunny bed of fertile, free-draining soil with plenty of organic matter. Choose ground where no brassica has grown for at least four years, to lower the risk of clubroot (Plasmodiophora brassicae).

A home pH kit shows whether lime is needed at all, and the soil pH article explains how to adjust it.

Container growing

The Kailaan line in the store makes a compact plant, so a large pot on a sunny balcony or courtyard suits it. A pot at least 30 cm across and 25 cm deep holds about 15 L, enough for one plant kept for side shoots. Fill it with premium potting mix and check that it has drainage holes.

• Water: check daily in warm weather and water whenever the top 2 cm of mix feels dry, as pots dry out much faster than beds.
• Feed: fish and seaweed blend at 25 mL per 9 L, fortnightly from the first true leaves. Or mix a controlled release fertiliser for containers into the mix at planting.
• Position: full sun through the cool months; move the pot into afternoon shade once the weather heats up.

Sowing Seeds

Sow Chinese broccoli where it is to grow, or raise it in cells and plant it out young.

Sowing direct

• Sow about 6 mm deep in rows 25 cm apart.
• Firm the soil lightly and water with a fine rose.
• Keep the surface damp; seedlings usually appear in 5 to 15 days.
• Thin in stages, as set out in Thinning.

Starting under cover

• Sow two or three seeds per cell of seed-raising mix, 6 mm deep.
• Snip out all but the strongest seedling once true leaves show.
• Plant out 3 to 4 weeks after sowing, at three or four true leaves.
• Harden off first (stand the tray outdoors a little longer each day for about a week).

Water transplants in with seaweed solution at half strength, 15 mL per 9 L, then mulch around each plant.

Care by growth stage

Thick, tender stems come from steady growth without a check, so even moisture and a moderate supply of nitrogen matter more than heavy feeding. Weeks count from sowing.

Mesh keeps out butterflies and moths, but it also shuts out the birds and wasps that eat aphids, so sap suckers can multiply underneath. Lift it to weed in the early morning or late afternoon, when the butterflies are not flying.

Thinning

Final spacing decides the harvest: crowded plants give slim, tender single stems, while wider plants keep sending up side shoots for weeks. Room between plants also lets leaves dry quickly, which slows downy mildew and white blister.

• First pass: once true leaves show, thin seedlings to about 5 cm apart.
• Second pass: at about three weeks, thin to the final spacing and cook the seedlings you pull.
• Lower leaves: strip off any that yellow and bin them, so the base of each plant stays airy and dry.

Companion planting

Scattering Chinese broccoli among other crops makes it harder for caterpillars to move from plant to plant. Nearby flowers feed the wasps that parasitise them.

Grows well with

• Beetroot and carrots, low crops that leave the brassica in full light.
• Climbing beans or sweet corn on the sunny side in hot districts, as living shade for a late sowing.
• Dill and coriander left to flower, whose blooms feed parasitic wasps and hoverflies.

Keep apart

• Broccoli, cabbage, kale, Chinese cabbage, choy sum and bok choy massed in one block, as they share caterpillars, aphids and clubroot.
• Shepherd's purse, mustard, wild radish and wild turnip, brassica weeds that harbour clubroot or cabbage aphid.

Harvesting Stems and Shoots

Cut the main shoot once the flower buds have formed but before any open, usually 7 to 12 weeks from sowing.

• Use a sharp knife and take a stem 15 to 20 cm long with its small leaves.
• Cut the main stalk fairly low, so the plant sends up side shoots.
• Expect the first side shoots about a week later.
• Pick in the early morning, when stems are crisp and full of water.
• Keep cutting every few days, more often in warm weather, before buds open.

Chill the shoots soon after picking, wrapped in a damp cloth or a bag in the crisper. Use them within about four days, and keep them away from fruit giving off ethylene, the ripening gas, as they are sensitive to it. Stems, leaves and buds are all eaten: stir-fry them with garlic and ginger, or blanch and serve with oyster sauce.

Common problems

Plants flowering while small. Warm weather and fast-grown transplants are covered in Three mistakes that matter. A spell of cold on young plants can also trigger early flowering, which is why midsummer sowings crop most reliably in the cool zone.

Tough, woody stems. Shoots left until the flowers open, or a dry spell that checks growth, give stringy stems, so water evenly and pick young.

Few side shoots after the first cut. A main stalk cut high, or a hungry plant, usually gives fewer and thinner side shoots. Cut low and feed after the main cut, as set out in Care by growth stage.

Gaps along the row. Seed sown too deep, or a surface left to dry out before the seedlings appear, are the usual causes; resow into the gaps. Read more

Seedlings falling over at soil level. Damping off takes hold in cold, wet, crowded trays with little air movement. Read more

Chewed seedlings and slime trails. Snails, and slugs to a lesser extent, are the worst pest of Asian greens. Pick them off on damp evenings, or set a beer trap. Read more

Pests and diseases

Caterpillars and sap suckers cause most of the damage, while the diseases follow cool, damp weather or wet, acid soil.

Cabbage white butterfly (Pieris rapae). Its velvety green caterpillars chew ragged holes and foul the leaves with droppings, and one female can lay up to 800 eggs. Pick caterpillars off by hand, or spray small ones with Bacillus thuringiensis, a bacterial insecticide that affects only caterpillars, as the label directs. It can also harm the caterpillars of other butterflies and moths, so spray only affected plants. Read more

Diamondback moth (Plutella xylostella). Plump, bright green caterpillars about 10 mm long feed under the leaves, leaving thin windows that tear into holes. In trials on Sydney Basin farms, gai lan drew far more of them than choy sum grown alongside. Green looper caterpillars, which arch into a loop as they move, chew the same leaves. Mesh and Bacillus thuringiensis work on both. Read more

Cabbage aphid (Brevicoryne brassicae). Dull grey-green aphids up to 3 mm long form blue-grey colonies coated in whitish powder, often in the shoots, and spread turnip mosaic virus. Hose them off, then spray insecticidal soap as the label directs. Read more

Downy mildew (Hyaloperonospora parasitica). A white, fluffy growth forms under seedling leaves, with black speckling above, mostly in cool weather; young plants suffer most. Thin on time and pull up brassica weeds. Read more

White blister (Albugo candida). White, dusty blisters form under the leaves, with yellow to brown spots above, when leaves stay wet from dew or rain. It spoils the look of the crop but poses no risk to the people eating it, so remove the worst leaves and bin them.

Clubroot (Plasmodiophora brassicae). Knobbly galls swell on the roots, so plants yellow, wilt and stop growing, and its spores can survive in soil for up to 20 years. Pull affected plants with their roots and bin them, never compost them.

Prevention first

• Lift the mesh once a week and turn a few leaves to check for eggs, caterpillars and aphids.
• Water at soil level, heavily and less often, so the leaves dry quickly.
• Clear spent plants straight after the last pick, as downy mildew and white blister carry over on debris.
• Clean soil off tools and boots after working a bed that has grown clubroot.

Tips

1. Kailaan is an heirloom, so seed saved from it can come true. It crosses with broccoli, cauliflower, cabbage and kale, which share its species, so let only one of them flower at a time.
2. White flowers set kai lan apart from broccoli and broccolini, which both open yellow, a handy check on a mixed bed.
3. Leave one unfed brassica outside the mesh as a sacrificial plant. It lures egg-laying butterflies away and, in time, the wasps that parasitise their caterpillars.