How to Grow Warrigal Greens in Australia

Warrigal greens (Tetragonia tetragonioides), also called New Zealand spinach or Botany Bay spinach, is a sprawling groundcover in the ice plant family, Aizoaceae. It is grown for its fleshy leaves and soft tips. It grows wild in every state except the Northern Territory and shrugs off heat, salt spray and poor soil. It keeps cropping through summer when spinach has bolted. The usual mistake is treating it like spinach: it wants warm soil, room to roam and blanching before it is eaten.

Three mistakes that matter

1. Sowing dry seed into cold soil. The woody seed is slow to take up water, and in cool soil it can sit for weeks without sprouting. Soak it first, and wait until the soil has warmed to the range in When to plant.
2. Planting into soggy ground. Wet feet are what this coastal plant handles worst, and waterlogged roots can rot. Grow it in free-draining soil, a raised bed or a pot, and water only when the top few centimetres dry.
3. Giving it too little room. One plant can spread 1.5 to 2 m, smothering neighbours and then self-sowing across the bed. Space plants 45 to 60 cm apart in a patch of their own, and pinch the tips often.

When to plant

Warrigal greens is frost tender, so sow it once the danger of frost has passed and the soil sits between 18°C and 35°C. In most zones that means spring into early summer, and in the tropics the dry season. One sowing crops for months, so there is no need for repeat rows.

At the cold edge of a window, start seed in pots under cover and plant out once frosts end. At the hot edge, sow into a shaded, well-watered patch, or wait for the heat to break.

Site, soil and setup

A plant of beach dunes and estuaries, warrigal greens asks for drainage first and richness a distant second. It copes with salty, windy coastal sites.

Container growing

The roots are shallow, so a wide pot matters more than a deep one. A 40 cm pot, about 28 L, holds one plant, and its stems can trail over the rim. Fill it with premium potting mix, never garden soil. There are no compact varieties to choose between: the one line the store sells grows well in a pot.

• Water: water when the top few centimetres of mix feel dry, and never leave the pot sitting in a saucer of water.
• Feed: worm casting liquid diluted to weak tea colour, every week or two once the plant is growing strongly.
• Position: full sun to part shade; in hot inland gardens, a spot with afternoon shade.

Sowing Seeds

Soak the seed, then sow it direct where the plants will grow or start it in pots for an earlier crop.

Preparing the seed

Each knobbly seed is really a hard, woody fruit with several seeds inside, so one sowing can send up more than one seedling. Soak the seed in warm water for at least 3 hours, or overnight, and sow it straight away. Soaking softens the hard coat and speeds germination. Seed soaked in cold water takes longer: allow about 12 hours.

Sowing direct

• Sow 5 to 10 mm deep, 15 to 30 cm apart, once the soil has warmed.
• Keep the surface damp; seedlings usually appear in 10 to 20 days, and not all at once.
• Thin to the strongest seedling at each spot at 2.5 to 5 cm tall, then to one plant every 45 to 60 cm.

Starting in pots

Pots give a head start where spring is short, or where snails patrol the bed.

• Sow one soaked seed per small pot of seed-raising mix, at the same depth.
• Plant out 4 to 6 weeks after sowing, once frosts have finished.
• Harden off (accustom seedlings to sun and wind over about a week) before planting out.
• Water in with seaweed solution at half strength, 15 mL per 9 L.

Care by growth stage

Drainage, steady picking and a light hand with feed decide this crop. Hungry or unpicked plants flower early and slow their leaf growth, while soggy soil brings rot. Weeks count from sowing.

If growth stalls in poor, sandy soil, scratch in a light dose of all-purpose controlled release granular (NPK around 14-5-10) at the label rate.

Pinching and Harvesting

Every pick is a prune. Regular trimming keeps the plant compact and pushes out fresh, tender shoots, and an unpicked plant turns woody and sets seed.

• Pinch out the growing tips weekly once the plant is established, even when the kitchen needs none.
• Cut long runners back to a leaf joint before they root where they are not wanted.
• Trim stems climbing into shrubs or crops alongside.
• Shear off flowering tips before the seed turns brown and woody, unless you are saving seed.
• Pull unwanted self-sown seedlings while they are small.

Warrigal greens is native, and it is not on the declared weed lists of Queensland or Tasmania. It self-sows freely, though, and counts as an agricultural weed in parts of Queensland, so keep it from spreading beyond the garden.

Companion planting

Its shallow roots and spreading habit make it a ground layer under taller plants, and a poor neighbour for small, slow crops.

Grows well with

• Citrus, which have shallow roots of their own and benefit from a living mulch that shades the soil.
• Avocado and other fruit trees, whose canopy gives the dappled shade warrigal greens tolerates.
• Shrubs at the bed edge, which it will happily climb rather than smother the vegetables.

Keep apart

• Lettuce, carrots and other low, slow crops, which its runners swamp.
• Tomatoes and cucurbits, which share root-knot nematode with it and keep numbers building in the bed.

Harvesting Leaves

Start picking once the plant is spreading well, usually 8 to 10 weeks after sowing, taking the young tips.

• Pinch or snip the growing tips, about 8 to 10 cm long, with their young leaves.
• Pick young leaves from along the stems; older leaves are tougher.
• Leave the thicker, older stems on the plant, since only the leaves and young stems are eaten.

Picked leaves keep for up to 2 weeks in the fridge. Once blanched, use them as you would spinach, in stir-fries, soups, quiches or a pie with feta. The leaves hold up to heat better than spinach.

Common problems

Gaps in the row. Seedlings come up unevenly over two to three weeks, so wait before resowing. Cold soil and unsoaked seed, set out in Three mistakes, make it worse.

Early flowering, few new leaves. An unpicked or starved plant switches to flowers and seed. Pinch as set out in Pinching and Harvesting, and feed as in Care by growth stage.

Tough, strong-tasting leaves. Older leaves are tougher, and dry spells dull the flavour, so pick young tips and keep moisture steady while picking.

Dying back in winter. Frost and cold weather end growth, and the plant dies back in winter in most zones; in frost-free gardens plants can live on as perennials.

Seedlings everywhere. Woody seed dropped from last season's plants comes up through the bed in spring; pot up the keepers and pull the rest.

Pests and diseases

Few pests trouble warrigal greens, and most do little more than nibble an established plant, but these are recorded on it in Australian gardens.

Snails and slugs (class Gastropoda). Older plants are rarely touched, but young seedlings can vanish overnight in damp weather, leaving slime trails. Hunt them by torchlight after rain, set beer traps, and raise seedlings in pots until they are sturdy. Read more

Aphids (family Aphididae). Small soft-bodied insects cluster on soft tips and can spread mosaic virus, which leaves a mottled, stunted plant with no cure. Knock colonies off with a firm jet of water or spray insecticidal soap, and pull out any plant with mottled leaves. Read more

Two-spotted mite (Tetranychus urticae). Fine, pale speckling on the leaves, with webbing underneath once numbers build in hot, dry, dusty weather. Hose the leaf undersides on three mornings running and keep plants well watered. Read more

Root-knot nematode (Meloidogyne species). Tiny worm-like soil animals cause swollen galls on the roots, so plants wilt in the heat and stall. There is no home cure: pull affected plants and rotate as set out in Site, soil and setup. Read more

Prevention first

• Raise early seedlings in pots, out of reach of snails.
• Keep the soil free-draining and never leave plants standing in water.
• Check soft tips weekly for aphids, and hose them off early.
• Water well through hot, dry spells, when mites build fastest.

Tips

1. Strike new plants from tip cuttings: root them in a glass of water, then pot them up once roots show.
2. For seed, let a few flowers ripen until the seed turns brown and woody, then collect it and store it dry for spring.
3. Warrigal greens survives salt spray, so in a seaside garden it suits the exposed, seaward side of the patch.
4. Surplus picking makes a treat for the chooks.
5. Malabar spinach and Egyptian spinach are two other heat-loving leafy greens, but they are different plants with their own guides.