Summer is the main planting season for New Zealand's classic warm-season vegetables: the crops that need real heat and a long frost-free stretch to produce well. Timing still varies significantly by region, so it's worth planting to your own area's calendar rather than a single national date.
In Auckland and the Bay of Plenty, the warm-season planting window opens earliest and runs longest: tomatoes, cucumber and sweetcorn from September, capsicum and chilli from September, pumpkin from September to November, zucchini from September through to January, and dwarf and climbing beans from September. Basil, being more frost-tender than most vegetables, is best left until October in the north.
In Waikato and Wellington, most of these same crops shift a month or so later. Tomatoes, cucumber, capsicum, chilli, zucchini, sweetcorn and pumpkin go in from October, along with dwarf and climbing beans. Basil follows in November.
In Canterbury, warmth arrives later still. Tomatoes, sweetcorn and pumpkin can go in from October, while cucumber, capsicum, chilli, zucchini and both dwarf and climbing beans wait until November. Basil waits until December. Otago is the most compressed of all: tomatoes from November, zucchini, sweetcorn, pumpkin and both dwarf and climbing beans in November, and cucumber and basil not until December. Capsicum and chilli don't have a reliable outdoor window in Otago at all, and are better grown in containers or under cover there.
Kumara is worth a specific mention: it needs around five frost-free months above roughly 17°C to bulb up properly, which makes it a North Island staple. It can be planted October-December in Auckland and the Bay of Plenty, and in November in Waikato/Wellington and Canterbury, but it isn't a realistic outdoor crop in Otago.
Across all regions, hold off on tender summer crops until you're confident the last frost has passed for your area. A warm spell in early spring doesn't guarantee frost is done. Losing a tray of tomato or capsicum seedlings to one cold night is one of the most common and avoidable setbacks in a New Zealand summer garden.
Losing a tray of tomato or capsicum seedlings to one cold night is one of the most common and avoidable setbacks in a New Zealand summer garden.