When to plant spinach and silverbeet

Planting months by climate zone

Both charts come from the same data as the planting calendar. Tap a zone for its full calendar and the towns it covers.

English spinach

Silverbeet

sow or plantnot recommendedthis month

The two charts are almost mirror images in the south. Spinach fills the cooler half of the year, and silverbeet the warmer half, running from spring to autumn. In the tropics both are dry-season crops, April to July. In New Zealand, spinach skips winter everywhere. In the cool south it has only March, April and September.

Why spinach bolts in spring

Oregon State University's vegetable guide explains that long days and rising temperatures push spinach to bolt, sending up a flower stalk and ending the harvest. Bolting is also more likely if young plants are chilled, at about 4–16 °C, and when plants are crowded. Spinach grows best at about 10–17 °C. So in practice:

• Autumn and winter sowings are the safest, because the plants mature while the days are short.
• For spring sowings, sow early and choose a variety described as slow to bolt. Oregon State stresses variety choice for late-spring crops.
• Thin the seedlings to the 10–30 cm spacing in the calendar, because crowding adds to the bolting risk.

Soil temperature for sowing

Both crops germinate in cold soil, but spinach dislikes heat. The germination table by J. F. Harrington of UC Davis, republished by Oregon State University Extension, gives these figures:

The table puts spinach's range at 2 °C to 29 °C. It germinates best at 7–24 °C, and at 21 °C for the fastest start. Swiss chard, which is silverbeet, ranges from 4 °C to 35 °C, with 10–29 °C best. That extra tolerance of warm soil is one reason silverbeet can be sown into summer.

Growing silverbeet

• Sow or plant 30 cm apart. Silverbeet can be sown direct or planted as seedlings.
• Pick the outer leaves and leave the centre growing. One planting then keeps producing for months.
• Shade it in the hottest weeks, as the calendar suggests, and keep the water up. See the watering calculator for run times.
• Pots: silverbeet wants 15–23 litres of mix, about a 400 mm pot. English spinach manages in 4–11 litres, as in the pot size guide.
• Rotation: spinach, silverbeet and beetroot are all in the beet family. Move them around together in a crop rotation.

Warrigal greens, a native alternative

Warrigal greens (Tetragonia tetragonioides) are an Australian native, also called New Zealand spinach. Sustainable Gardening Australia describes a groundcover about 1.5 m across, perennial in temperate and warm areas and annual in cool ones, and calls it a wonderful spinach substitute. You pick the fleshy, triangular leaves. Soak the seed overnight before sowing.

One caution: the leaves are high in oxalic acid. Sustainable Gardening Australia advises blanching them for 1–2 minutes in boiling water before eating. Only the leaves are eaten.

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