August is the biggest sowing month of the year in New Zealand. After a quiet June and a two-crop July, more than a dozen sowing windows open at once in every region: broccoli and kale, broad beans, shallots, quick greens and an indoor tomato start. The catch is frost. It's still frost season everywhere this month, so the real question is what to start under cover and what can go straight into cold ground. In Northland and Auckland, the tomatoes sown in June are already ready to transplant.

Quick Answer: Plant These Anywhere in NZ

Eighteen crops are inside their planting window in every NZ growing zone this August. They fall into four groups.

Frost-hardy, direct sow now:

  • Broad beans (sow August–October)
  • Beetroot and silverbeet (sow August–May)
  • Radish (sow August–April)
  • Onion (sow July–September) and shallot (sow August–September)

Brassicas, newly opened:

  • Broccoli (sow August–November) — frost-hardy, raised in trays
  • Kale (sow August–October) — frost-hardy, direct sow or trays

Quick greens and roots, recorded as frost-tender:

  • Pak choy (sow August–May), mizuna (sow August–December), turnip (sow August–October) and coriander (sow July–November)

Start indoors in trays:

  • Tomato, capsicum and eggplant — in the temperate and cool/mountain zones these open now (August–November). In the sub-tropical zone they opened in June and are now ready to transplant (see below).

Lemon, mandarin and orange also stay in their planting window, which closes in September.

Notes from the planting data

  • Broccoli is raised in trays and transplanted at four to six weeks. Net young plants against white butterfly from the day they go out — see White Butterfly and Cabbage Moth on NZ Brassicas.
  • Kale can be direct sown or tray-raised. Once established, frost improves its flavour rather than threatening it.
  • Broad beans are direct sown. Pinch out the growing tips once flowering starts to reduce aphid pressure — see Aphids in the NZ Vegetable Garden.
  • Shallot has the tightest window this month (August–September). Plant bulbs 5cm deep and 15cm apart.
  • Onion is a long-season crop, roughly 160–200 days, and dislikes high-nitrogen soil.
  • Turnip has a narrow window because it dislikes summer heat. Late winter and spring is its real season.
  • Radish and mizuna are quick crops. Sow a little every two to three weeks rather than one big batch.

The frost-tender greens are sown now regardless. In the coldest gardens, though, a cloche or cold frame makes the difference between steady germination and seed sitting in frozen soil.

Not sure which zone you're in? The NZ frost dates guide covers it by town.

Sub-Tropical: Northland, Auckland and Coastal Taranaki

The far north is two months ahead on summer crops. Tomato, capsicum and eggplant were sown in June, and this month they enter their August–October transplant window. Frost season here runs until September, so plant them out once your own garden is past its last frost, not on the first warm day.

Two more frost-tender crops are on the sowing list here:

  • Cucumber opens its sowing window this month (August–November). It's raised in trays first.
  • Basil is still in its July–December window, raised under cover until its September transplant window.

Tomato, capsicum and eggplant sowings are also still open until September, if you want a second batch.

On the harvest side, Jerusalem artichoke, carrot and lime all finish this month. Lemon, mandarin, orange and tamarillo carry on.

Temperate: Most of the Country

The eighteen crops above are the August list. Tomato, capsicum and eggplant open as an indoor start this month. Transplanting comes later in spring, once the frost season has passed. An August sowing buys lead time, but don't sow the whole packet at once. Seedlings can get leggy if a cold spring delays planting out.

With this many windows opening at once, tray space is usually the bottleneck, not soil. Give trays to broccoli and the tomato family first, since they need weeks before transplanting. Sow the direct-sow crops — beetroot, silverbeet, radish, broad beans — whenever a bed comes free.

Basil, peas, cucumber and courgette aren't open here yet. Basil and peas open in September, and the cucurbits later still. The harvest is down to its last few: carrot and Jerusalem artichoke both finish this month. Lift the rest, and keep a few artichoke tubers aside for replanting.

Cool/Mountain: Central Otago, Queenstown and the Central Plateau

On paper, cool/mountain gardens get the same eighteen crops as the temperate zone. In practice, frost here runs right through to November, and many high-country gardens are still frozen in August. Treat the list as what the season allows, not a sign that winter is over.

That makes the indoor start the most useful job this month:

  • Tomato, capsicum and eggplant started now may wait until late spring before it's safe to plant them out, so sow modestly. Tomatoes are demanding in short, cool seasons. Why Tomatoes Fail in Wellington covers the common pitfalls.
  • Broccoli and silverbeet both take well to a tray start under cover.
  • Kale is the crop that actively wants the cold.

Outdoors, the frost-hardy crops (broad beans, beetroot, onion, shallot, radish) can go in where the soil is workable, but germination is slow in cold ground. A cloche helps broad beans establish in the hardest-frost gardens. Carrot and Jerusalem artichoke finish their harvest this month.

Recommended Cultivars

These cultivar picks for August's sowings come from NZ suppliers:

  • Broccoli — Belstar F1 (Kings Seeds NZ); de Cicco, Purple Sprouting (Koanga Institute)
  • Kale — Red Russian, Westerland, Noble (Kings Seeds NZ)
  • Broad beans — Coles Prolific (Kings Seeds NZ); Suttons Dwarf, Red Seeded (Koanga Institute)
  • Beetroot — Detroit Dark Red, Golden Detroit (Kings Seeds NZ)
  • Silverbeet — Bright Yellow (Kings Seeds NZ); Margaret Dale (Koanga Institute)
  • Coriander — Picante (Kings Seeds NZ); NZH (Koanga Institute)
  • Tomato — Small Sweet Orange, Russian Red, Margaret Curtain (Koanga Institute)
  • Cucumber (sub-tropical) — Spacemaster, Medici F1 (Kings Seeds NZ)
  • Basil (sub-tropical) — Genovese Giant (Kings Seeds NZ); Genovese (Koanga Institute)

There are no approved cultivar picks yet for onion, shallot, capsicum, eggplant, mizuna, pak choy, radish, turnip or the citrus trees.

August Garden Jobs, Anywhere in NZ

These are general late-winter jobs, not zone-sourced planting data:

  • Get trays going early. Starting seed now avoids everything needing transplanting at the same time in spring.
  • Net brassicas at planting, not at the first sign of damage.
  • Don't direct-sow tender crops outside. Tomato, capsicum and eggplant seed sown into cold August soil mostly just rots.
  • Harden off seedlings gradually before they go outside, wherever transplanting is due.

Next Steps

For month-by-month sowing and harvest timing in your area, see the full planting calendar for your zone: