May is a genuine milestone in this zone's calendar: it's the first month all year with any frost risk at all here, running through to September. Gardeners in the rest of the country have already been managing frost for a month or two by the time it finally shows up in a sub-tropical garden — which is exactly why this zone's garlic, sown back in March, and its citrus, already in the ground since April, were both timed to be established well before this point rather than caught out by it.
Quick Answer: What to Sow Now
Seven crops are open for sowing this May: beetroot, carrot, lemon, mandarin, orange, pak choy and silverbeet.
Frost Finally Arrives
Nothing changes about how these seven crops are handled this month — none of them are frost-tender, so May 1 doesn't ask for any new precautions. What it does mark is the end of a run of months where this zone had essentially no cold-weather planning to do at all. From here through September, it's worth treating any newly transplanted citrus with the same care a temperate gardener already applies without thinking about it.
That's a genuinely different rhythm to the rest of the calendar this site covers. Temperate and cool/mountain gardeners spend a good chunk of the year working around an active frost window; a sub-tropical gardener spends most of the year without one, then gets a short, late version of it for a few months from here. The practical habits — checking forecasts before a cold night, having frost cloth on hand for young plants — aren't things this zone needs to think about most months, so it's worth actually setting them up now rather than assuming the season further south's precautions.
Citrus, Still Going In
Lemon, mandarin and orange all remain inside their planting window this month, same as April — the window runs April through September uniformly across NZ's three zones, so there's no particular rush specific to May, just continued opportunity. Best Lemon, Best Mandarin and Best Orange Varieties are worth a look if you haven't chosen a cultivar yet.
Beetroot, Carrot, Pak Choy and Silverbeet
All four remain well inside long sowing windows with nothing month-specific to flag this time around. Direct sow beetroot and carrot, keeping the carrot bed evenly moist through germination, and get silverbeet or pak choy in wherever a summer crop has just finished up.
Jerusalem Artichoke Joins the Harvest List
Jerusalem artichoke's harvest window opens this month and runs all the way through to August. The sourced guidance here is a useful piece of counter-intuitive timing for a month frost has just arrived: cold weather actually improves tuber colour, and mild, drier sites can leave tubers in the ground and dig them as needed right through winter rather than lifting the whole crop at once. Frost showing up this month isn't a reason to rush this particular harvest.
Also Harvestable This Month
Basil, capsicum, courgette, eggplant, feijoa, lettuce, passionfruit, peas, radish, tamarillo, tomato and yacon are all still cropping this month.
Timing Notes for Sub-Tropical Gardens
The practical upshot of this zone's May–September frost window is that it's short and late relative to the rest of the country, not that it's severe once it arrives. Established plants — the citrus and garlic already in the ground, the perennial crops like feijoa and tamarillo — aren't newly at risk just because frost has technically opened; it's new, unestablished plantings that need the most caution from here, particularly anything transplanted in the last month or two that hasn't had time to build the root system a mature plant relies on to shrug off a cold night.
Recommended Cultivars
- Beetroot — Bull's Blood (Kings Seeds NZ, Koanga Institute)
- Carrot — Akaroa Long Red (Koanga Institute), Amsterdam Sprint (Kings Seeds NZ)
- Silverbeet — Bright Yellow, Ford Hook Giant (both Kings Seeds NZ)
Lemon, mandarin, orange and pak choy don't have an approved cultivar pick sourced for this zone yet.
Know your zone? Explore the full NZ Sub-Tropical Planting Calendar for month-by-month sowing and harvest timing.