A bare or patchy carrot row almost always comes down to moisture, not the seed itself — carrot is sown shallow and takes two to three weeks to emerge, with nothing in reserve if the surface dries out even briefly during that stretch. Surface crusting, sowing too deep, and old seed round out the real culprits, roughly in that order, and cold soil barely enters into it here.

The Likely Causes

  1. The bed drying out mid-germination. Even a short gap without water partway through this crop's long emergence window is enough to kill seed that's already started sprouting — and there's no visible sign above ground either way until you know which outcome you got.
  2. A hard cap forming on top of the soil. Rain or watering on heavy or poorly worked ground can bake the surface into something carrot's thread-fine seedlings simply don't have the strength to break through, even where the seed itself sprouted just fine underneath.
  3. Sown deeper than it should be. Carrot seed only wants about 6mm of cover — buried further than that, especially in heavier soil, the shoot can run out of reserves before reaching daylight.
  4. Seed that's past its useful life. Reliable viability runs about a year in normal home storage, dropping further the second year and becoming unpredictable by the third — a row sown from an old leftover packet can simply have too few live seeds in it to show.

Why Cold Isn't Really the Story Here

Carrot's direct-sow window doesn't shift by zone — September through May, harvest December through August, per Egmont's culture guide, the same everywhere in NZ. What genuinely differs is how quickly the ground actually clears the roughly 10°C threshold carrot needs, and this zone gets there fastest of the three, thanks to the shortest frost season by a wide margin. Cold soil essentially drops out as an explanation across the whole sowing window here — if a row isn't coming up, moisture inconsistency or a crusted surface is almost certainly why. That warmth comes with a real trade-off, though: this zone's typically higher rainfall and humidity make surface crusting after heavy rain a genuinely bigger risk here than in either other zone, so a light protective cover over a fresh sowing matters more, not less, despite the warmer ground underneath it.

Fixing It

  • Keep the surface consistently damp for the full two-to-three-week window, not only at sowing — little and often beats heavy and infrequent.
  • Cover the row straight after sowing, and check it daily. Newspaper, cardboard or shade cloth all work, but pull the cover the moment the first green shoots show — seedlings starved of light under a cover left too long die just as fast as dry ones do.
  • Get the bed properly worked before sowing, not after. Dig deep, break up clods, and mix in compost ahead of time on heavier ground so it doesn't cap over once watered — worth taking seriously given how much rain this zone typically gets.
  • Sow shallow and firm lightly — about 6mm of cover — then water in gently so seed doesn't wash out or get driven deeper.
  • Buy fresh seed rather than reaching for last-last season's packet, and if you're not sure how old it is, test a pinch on damp paper towel before you trust an entire row to it.

Cultivar Notes

Seven Koanga Institute cultivars are sourced for this zone: Akaroa Long Red, Juwarot, Kuroda, Oxheart, Paris Market, Touchon and White Belgium. Every one of them comes with identical growing instructions from the supplier — scatter the seed, cover it lightly, then lay an old sheet or 70% shade cloth over the bed until germination, taking it off once roughly 70% of seedlings have their first true leaves. Independent supplier practice landing on the same answer this brief's general guidance already gives is worth treating as real confirmation, not coincidence — and given this zone's own rainfall-driven crusting risk, following it matters more here than a grower further south might assume.

Next Season

Once a row is reliably coming up, carrot rust fly becomes the next real thing worth watching for — see Carrot Rust Fly in NZ — Protecting Your Carrot Crop for identification and control, including why sowing thinly enough to skip later thinning helps keep flies away from the row in the first place.

More on this zone: see the full NZ Sub-Tropical Planting Calendar →.