In a temperate garden, tomatoes usually ripen without much fuss — the warm season is long enough that season length isn't the problem it is further south. So when fruit sits stubbornly green here, the cause is generally something more specific: fruit that set too late, a plant carrying too much leaf, over-feeding, or a passing cool snap. Ripening runs best around 20–25°C and slows below about 12°C at night, so a cool spell can pause it — but in a warm summer, that's usually temporary rather than terminal.

Why it happens here

  1. Too much foliage or too much nitrogen. This is the most common cause. A dense, leafy plant shades its own fruit, and a high-nitrogen feed keeps it making leaves rather than ripening the tomatoes it already has.
  2. Late-set fruit. It takes roughly 6–8 weeks from flower to ripe fruit. Trusses that set late in the season may simply need more time — not a fault, just arithmetic. Your harvest window runs December to April, so there's usually room for them.
  3. A cool snap. Ripening slows below about 12°C at night, so a cold spell can stall things briefly. In a warm summer it typically picks back up when the warmth returns.
  4. Too hot (occasionally). In a heatwave above about 30°C the plant stops producing the pigments that colour the fruit, so it can stall at green or ripen unevenly with yellow shoulders. Less common than the leafy-plant cause, but worth knowing in a hot spell.

What to do now

  • Ease off the nitrogen and thin the canopy. This is the main fix: remove some leaves around the trusses to let warmth and light in, and switch from a high-nitrogen feed to a potassium-richer one so the plant puts energy into ripening.
  • Give late-set fruit time — if the plant is healthy and the season still has warmth in it, patience often does the job here.
  • Late in the season, ripen indoors. As autumn cools, pick mature green fruit and ripen it at room temperature in the dark (a drawer or paper bag, not a windowsill) — it colours up in a few days, and ripening needs warmth rather than sun.

What to change next season

  • Don't overfeed nitrogen once fruit has set — it's the easiest mistake to make.
  • Prune and stake so the plant isn't a shading jungle of leaves over its own trusses.
  • If a hot inland summer is stalling fruit at green, a little afternoon shade during heatwaves helps the plant keep making pigment.

This zone has the season on its side for tomatoes, so unripe fruit here is usually a fixable feeding or foliage issue rather than a lost cause.

Leaves curling as well? See Why Are My Tomato Leaves Curling in NZ Temperate?, or explore the full NZ Temperate Planting Calendar →.