March is when autumn arrives in New Zealand's cool/mountain gardens. The zone's frost-risk period runs March through November, so this is the first month a frost can turn up — and that single fact separates a cool/mountain March from a temperate one, where frost doesn't start until April. Warm-season crops are finishing here a full month earlier, and every new sowing has to be quick or cold-hardy enough to cope.

That makes March a narrower sowing month than February was. Last month, basil, climbing beans, courgette, peas and spinach were all still sowable; their windows have now closed. What's left is a short list of frost-tolerant roots and greens.

Quick answer: what to sow now

March is a sowing month in cool/mountain gardens for:

  • Beetroot
  • Carrot
  • Lettuce — last sowing month this season
  • Pak choy
  • Radish
  • Silverbeet

Every one of these is either frost-tolerant or fast enough to crop before the cold sets in — which is exactly why they're the sensible choices now that frost is on the table.

The dependable March sowings

Beetroot sows from August through May and harvests from October through July. It tolerates light frost, which matters this month in a way it didn't in midsummer. Direct sow and thin seedlings to around 10cm — beetroot dislikes being moved, so don't raise it in trays.

Carrot sows from September through May and harvests from December through August. Direct sow only; carrots resent transplanting. The one thing that decides whether you get an even stand is keeping the seedbed evenly moist until germination.

Silverbeet sows from August through May and harvests from October through July. It's the most weatherproof crop on this list — a hardy leafy green that will keep producing through winter once established, picked outer-leaves-first. Direct sow, or raise in trays to fill gaps left by finished summer crops. For the full year-round picture, see Growing Silverbeet Year-Round in NZ.

Pak choy sows from August through May and harvests from September through June. It can bolt in extended hot spells, but March's cooling nights work in its favour here, easing the pressure that troubles summer sowings.

Radish sows from August through April and harvests from October through June. It's quick enough to sow in short rows every couple of weeks rather than all at once — a useful gap-filler while the beds reorganise for autumn.

Lettuce sows from September through March and harvests from November through May, which makes March its final sowing month before the winter gap. Direct sow or raise in trays, and keep the succession rhythm going one last time — small amounts, not a whole packet — rather than sowing a single big batch you'll never eat through.

The summer harvest closing out

March is the last month for several warm-season crops in this zone, and the timing is tighter than in the temperate zone precisely because of the earlier frost.

Basil (harvest January–March), courgette (January–March) and tomato (December–March) all end their harvest windows in March here — a month sooner than temperate gardens, where the same crops run into April. Pick everything you can while the plants are still standing. If your tomatoes are still stubbornly green as the nights cool, Why Are My Tomatoes Not Ripening in NZ Cool/Mountain? covers what to do about it. Cooler nights and heavier autumn dew also lift late blight pressure — see Early and Late Blight on NZ Tomatoes for prevention.

Yacon has a harvest window of March alone in this zone (against March–April in temperate gardens). Its early first frost makes for a short, marginal season for this heat-loving South American crop, so lift the tubers as soon as frost hits rather than leaving them.

Jerusalem artichoke works the opposite way: its harvest window opens in March here (a month earlier than temperate), and the tubers can stay in the ground to be dug as needed right through winter — this zone's hard cold actually improves their colour.

Pumpkin also opens its harvest window this month (March–June). Leave the fruit until the skin resists a thumbnail, then cure it in the sun for a week or two before storing.

Also cropping through March: climbing beans (through May), broccoli, cucumber, onion, peas (through May) and spinach.

Timing notes for cool/mountain gardens

The rhythm this month tips decisively from starting to finishing. Frost changes the maths on anything warm-season, so don't gamble a bed on a late sowing that can't beat the cold — commit to the frost-tolerant roots and greens above, and put the rest of your effort into bringing the summer harvest home.

Clear spent crops as they tail off, work compost into the emptied beds, and you'll be set up for the cool-season planting that April brings.

Recommended cultivars

  • Beetroot: Bulls Blood (Kings Seeds NZ), or Bull's Blood (Koanga Institute) — deep-red foliage as well as roots, suited to autumn sowing.
  • Carrot: Amsterdam Sprint (Kings Seeds NZ), a fast, reliable all-rounder; or Akaroa Long Red (Koanga Institute), a heritage long-rooted type for deep, loose soil.
  • Lettuce: Buttercrunch or Coral Red (both Kings Seeds NZ), both comfortable at the cooler end of the sowing window.
  • Silverbeet: Ford Hook Giant (Kings Seeds NZ) for a heavy-cropping standard, or Bright Yellow (Kings Seeds NZ) for colour in the bed.

Know your zone? Explore the full NZ Cool/Mountain Planting Calendar for month-by-month sowing and harvest timing.