How to Grow Spinach in Australia

Spinach (Spinacia oleracea) is a fast-growing leafy annual in the amaranth family, Amaranthaceae, grown for its soft, dark green leaves. In Australia silverbeet is often called spinach too, but it is a different species, and so are summer stand-ins such as Warrigal greens. True spinach, often sold as English spinach, crops quickly through the cool months, and sowing it into lengthening spring days is the usual mistake.

Three mistakes that matter

1. Sowing into lengthening spring days. Long days and rising heat send spinach quickly to seed, and the leaves turn bitter. Sow mainly from autumn into late winter, at the times in When to plant.
2. Letting the bed dry out. Spinach is shallow-rooted and does not tolerate water stress, which is one of the commonest triggers for bolting (running to seed). Mulch with straw and water before the soil dries.
3. Sowing into acid soil. Spinach grows very poorly below pH 6.0. Test the soil and lime it at least four weeks before sowing: see Site, soil and setup.

When to plant

Spinach seed germinates in soil from about 5°C, most reliably between 10°C and 25°C, and patchily once the soil turns hot. Plants grow best in mild weather of about 10°C to 17°C, so time each sowing to crop before spring warmth and long days arrive. Sow a short row every few weeks for a steady supply.

At the warm edge of the window, sow a slow-bolting variety where it gets afternoon shade. At the cold edge, a cloche over young seedlings carries them through hard frost.

Site, soil and setup

Spinach wants full sun in winter and light shade as spring warms, which slows bolting. It needs rich, moisture-holding soil that still drains.

Container growing

A pot at least 40 cm wide and 30 cm deep, about 28 L, grows a few plants for picking. Fill it with premium potting mix, never garden soil, and sow 'Bloomsdale', 'Matador' or 'Baby Leaf F1'.

• Water: check daily and water before the mix dries out, because pots dry fast and dry mix sends plants to seed.
• Feed: fish and seaweed blend at 25 mL per 9 L fortnightly. A controlled release fertiliser for containers, mixed in at sowing at the label rate, can replace it.
• Position: full sun in winter; move the pot out of hot midday sun once spring arrives.

Sowing Seeds

Sow direct where the plants will grow, because moving seedlings disturbs the roots and can hasten bolting.

Sowing direct

• Water the bed the day before, then sow 10 to 20 mm deep in rows 20 to 30 cm apart.
• Drop a seed every 5 cm or so, and thin the seedlings later.
• Keep the surface damp, and seedlings appear in 5 to 10 days in cool soil.
• Mulch lightly with straw once the seedlings are up, keeping it clear of the stems.

Starting in punnets

Modules give an early start, provided the roots are barely disturbed at planting.

• Sow one seed per cell of seed-raising mix, at the same depth.
• Plant out at about 10 cm tall, without breaking the root ball.
• Harden off (accustom seedlings to sun and wind over about a week) before planting 20 to 30 cm apart.

Due to quarantine restrictions and our shipping policy, we cannot send some spinach seed to Western Australia; each product page says which.

Care by growth stage

Steady water and nitrogen decide this crop, because any check in growth pushes it towards flowering. Weeks count from sowing.

Water in the morning so the leaves dry before night, since damp evenings favour snails and downy mildew.

Thinning

Crowded spinach bolts sooner and catches downy mildew, so thin twice and eat what you pull.

• Thin to about 7.5 cm apart once seedlings are large enough to handle, keeping the strongest.
• A few weeks later, pull every second plant for salads, leaving the rest at least 15 cm apart.
• For full-sized plants of large types such as 'Viroflay', finish at 20 to 30 cm.
• Snip unwanted seedlings at soil level rather than pulling, so the keepers' roots stay put.
• Rows sown only for baby leaf need no thinning.

Companion planting

Good neighbours share the cool season, crop and clear quickly, or shade the row as spring warms.

Grows well with

• Peas and broad beans, cool-season partners whose tall rows can shade spinach from afternoon sun.
• Radish, which crops and is pulled before the spinach fills out.
• Onions, upright and slim, so they cast little shade over a low rosette.
• Strawberries, low plants that leave room for spinach between them.

Keep apart

• Beetroot, a relative in the same family that shares aphids and the viruses they carry.
• Pumpkin and zucchini, whose vines smother a low rosette as spring sowings mature.

Harvesting Leaves

Start picking when plants are about 10 cm high, usually 5 to 11 weeks from sowing.

• Cut outer leaves with scissors, and take no more than a third of the plant at a time.
• Cut rather than pull, which damages the roots.
• Pick regularly, since frequent picking prompts new leaves.
• For one big picking, cut the whole plant just above the base; well-rooted plants often regrow once.
• Pull and compost a plant once it sends up a flower stalk, because the leaves turn bitter.

Chill picked leaves straight away. Close to 0°C in high humidity, spinach keeps 10 to 14 days; warmer, it deteriorates quickly.

Eat young leaves raw in salads, and wilt larger ones briefly into soups, pies and stir-fries, remembering a big pile cooks down to little. Spinach is high in oxalate, and Queensland Health lists it among foods to avoid for people prone to kidney stones.

Common problems

Running to seed. A central stalk shoots up and the leaves shrink and turn bitter. Long days, heat, dry soil, crowding and cold shocks to young plants all set it off. Timing is most of the fix: see Three mistakes.

Patchy germination. Seed sown into hot soil comes up thinly or not at all; wait for cooler nights, or sow into a shaded, well-watered drill.

Slow growth in midwinter. Growth crawls in cold soil, so winter rows simply take more weeks; a cloche or straw mulch helps in frosty districts.

Tough, strongly flavoured leaves. Leaves coarsen as they age, so pick them young.

Pests and diseases

Few pests trouble spinach in the cool months, and these four are among the ones to watch.

Green peach aphid (Myzus persicae). Dark green to yellow sap-suckers that start on the lower leaves and move up, carrying viruses such as cucumber mosaic. Hose small colonies off or coat the leaf undersides with insecticidal soap, and let ladybirds and lacewings finish the job. Read more

Common garden snail (Cornu aspersum) and grey field slug (Deroceras reticulatum). Both chew soft young leaves, and seedlings are most at risk. Hunt by torch on damp nights, and if a bait is needed, choose an iron-based one. Read more

Downy mildew (Peronospora effusa). Yellow spots on the leaves, with purplish growth underneath, in cool, wet weather and dense rows. It already affects Australian crops, and new races keep overcoming resistant varieties. Space plants, remove affected leaves and choose a resistant hybrid. Read more

Damping off (Pythium species and Rhizoctonia solani). Seedlings rot before they emerge or collapse soon after, worst in clay, poorly drained soil and beds that grow spinach often. Sow into free-draining soil, water lightly at germination and rotate. Read more

Prevention first

• Sow in the cool months at the spacing above, so plants grow fast and dry quickly after rain.
• Water in the morning at the base of the plants.
• Clear weeds and rubbish that hide snails and host aphids.
• Rotate beds, and do not follow spinach with spinach.

Tips

1. For leaves through summer, grow a heat lover instead. Warrigal greens (Tetragonia tetragonioides), an Australian native, are cooked before eating. Malabar spinach (Basella alba) is a climbing vine, and Egyptian spinach (Corchorus olitorius) suits tropical and subtropical summers.
2. Perpetual spinach is a form of silverbeet with a spinach-like flavour, and it keeps cropping in warm weather instead of bolting.
3. Anzac Day is a fair marker for the main autumn sowing across the south; rows sown then crop through winter before spring bolting starts.
4. Sow a few seeds among taller crops such as sweet corn, whose shade can hold off bolting as days warm.