How to grow choy sum in Australia

Choy sum is a cool-season brassica that bolts rapidly in heat — the key is timing to avoid the peak of summer. It grows in a wider temperature range than many leafy greens and can be sown in both autumn and late winter/early spring.

Direct sow where the plants will grow — choy sum doesn't transplant particularly well but can be started in punnets and planted out carefully at a very young age (2 true leaves). Direct sowing is simpler and produces more even germination.

Spacing: 20cm between plants. Succession sowing every 2–3 weeks gives a continuous harvest rather than a glut.

Depth: Sow 1cm deep. Cover lightly with fine soil and keep moist. Germinates in 4–7 days.

Soil: Rich, moisture-retentive soil with good organic matter. Choy sum is a hungry, fast-growing plant — plenty of compost worked in before planting pays off in the short (40-day) production window.

Succession sowing: Choy sum has a short harvest window — it goes from ready-to-harvest to bolted over 1–2 weeks. Sowing a short row every 2–3 weeks avoids the feast-or-famine effect. A small, consistent harvest is more practical than a large one-time glut.

Pots and shallow containers work well for choy sum — it has a shallow root system and a short growing period. Window boxes, balcony planters, and even large pots are productive. This makes it excellent for balcony and urban gardeners who want to grow Asian greens without a large garden.

Raised beds are ideal — good drainage and easy access for the close-spaced succession plantings. A half-metre of bed space can support several rounds of choy sum through a cool season.

In-ground in regular garden beds is equally productive. Incorporate compost before each round of sowing.

Choy sum grows in full sun in cool weather but appreciates afternoon shade as temperatures climb. In hot weather (above 25°C) light shade significantly slows bolting. This makes it a useful plant for positions that are sunny in winter but have some shade from a structure or larger plant in the warmer months.

Water consistently — choy sum wilts quickly in dry conditions and stress accelerates bolting. Keep the soil consistently moist. Mulch to reduce moisture loss and moderate soil temperature.

Harvest the whole plant when it starts to produce flower buds but before the flowers fully open. At this stage — typically 40–50 days from sowing — the stems are crisp and sweet, the leaves are tender, and the flower buds are just beginning to show yellow.

Cut the plant at the base, leaving a few centimetres to potentially regrow (not always reliable, but worth trying).

The entire harvest — stems, leaves, and flowers — is edible. In the kitchen, choy sum cooks quickly: 2–3 minutes in boiling water or a brief stir-fry. It pairs with oyster sauce, garlic, and ginger.

Once flowers are fully open, the stems become tougher and the plant is past its best eating quality — though the flowers remain edible and are a nice garnish.

Bolting — premature flowering — is the primary issue in warm weather. Ensure cool temperatures (below 25°C) and consistent moisture to delay it. Once the plant bolts, harvest immediately before quality drops further.

Cabbage moth and white butterfly caterpillars — a universal brassica problem. Check undersides of leaves for eggs. Bt (Bacillus thuringiensis) spray is effective and safe. Row covers over young plants prevent egg-laying.

Aphids cluster on new growth and flower buds. Spray off with water or apply neem oil. Beneficial insects (especially in gardens with marigolds) provide natural control.

Powdery mildew in humid conditions. Improve airflow, avoid overhead watering, harvest before it becomes a major issue. Given choy sum's short growing cycle, mildew rarely has time to build up significantly.

Slugs and snails attack seedlings. Iron-based pellets around newly sown rows are effective.

Choy sum fits naturally into the Asian vegetable garden alongside spring onion, coriander, chives, and garlic. These plants all share cool-season timing and complement each other in the kitchen.

Marigolds planted at the edges of the bed deter soil pests and attract beneficial insects that prey on caterpillars and aphids. Chives and spring onion as border plants provide some deterrence to pests that attack brassicas.

As a fast-growing annual, choy sum works well as a quick catch crop between slower-growing vegetables.

Standard Choy Sum — the common form sold in Australian Asian supermarkets and garden centres. Green stems, yellow flowers. Fast-maturing and reliable.

Hon Tsai Tai (Purple Stem Choy Sum) — distinctive purple-tinged stems and leaves with yellow flowers. Slightly more cold-tolerant than standard choy sum. The purple colouration intensifies in cooler weather. Same flavour; more ornamental appearance.

Early Choy Sum — a fast-maturing selection, ready in as little as 35 days. Suited to the shorter windows at the edge of the cool season. Good for Sydney and Brisbane gardeners who want to squeeze in sowings in the warmer months.