May pulls in two directions in New Zealand's cool/mountain gardens. The autumn sowing season is shutting: beetroot, carrot, pak choy and silverbeet all close their windows at the end of this month. But one crop is only just beginning — garlic's window opens in May, and in this cold zone that's a full month behind the warmer temperate gardens, which are already closing garlic out. Plant it now, and everything else, and the growing side of the garden is essentially set until spring.
Frost has been part of the picture since March here, so nothing on this list is troubled by cold — these are the crops chosen precisely because they can take a cool/mountain winter.
Quick answer: what to sow now
May is a sowing month in cool/mountain gardens for:
- Garlic — window just opening
- Beetroot — last month to sow
- Carrot — last month to sow
- Pak choy — last month to sow
- Silverbeet — last month to sow
Garlic is the crop with room ahead of it; the other four are on their final call before the winter gap.
Garlic: the one crop with its window opening
While temperate gardens treat May as the last chance to get garlic in, cool/mountain gardens are only starting. Garlic's window here runs May through June — the latest of New Zealand's zones. The reason is the cold itself: garlic needs a sustained spell of winter chill to turn a single planted clove into a full bulb, and this zone delivers that reliably, so there's no rush to beat the warm weather that warmer regions worry about.
Plant individual cloves 5cm deep and 15cm apart into ground you've enriched with compost. From a May planting, garlic runs about seven months to a December–January harvest. For the full timing picture in a cold NZ region — and it's worth reading before you commit a bed — see When to Plant Garlic in Canterbury NZ. Getting the bed right now also heads off trouble later: Rust and White Rot in NZ Garlic covers the two diseases most worth planting against.
A note on the timing: the exact May–June window for this zone is our own guidance for the coldest gardens rather than a figure lifted from a single supplier — most NZ seed houses quote a broad April–May planting without splitting it by zone. The general principle (colder gardens plant later) is sound; treat the precise month as a recommendation, not gospel, and adjust to your own altitude and frost pattern.
Last call for the autumn sowings
These four all close their sowing windows at the end of May, so if you want them in this autumn, this is the month.
Beetroot (sow August–May, harvest October–July) takes a cold-season sowing without complaint — it handles light frost. Put seed straight in the ground and thin the seedlings to about 10cm; it doesn't take kindly to being lifted and moved.
Carrot (sow September–May, harvest December–August) has to go in where it will grow — shift a carrot seedling and the root forks. Germination is slower now than earlier in autumn, so the thing that matters most is not letting the seedbed dry out before the seed breaks through.
Pak choy (sow August–May, harvest September–June) is the quick one here. The summer heat that sends it to seed is long past, so a May sowing gives you a fast, mild green with none of the bolting risk it carries in January.
Silverbeet (sow August–May, harvest October–July) is the crop that will still be feeding you in July. Sow it direct, or raise a few in trays to fill gaps as other beds empty — once it's up, taking the outer leaves and leaving the middle keeps it going right through the cold. Growing Silverbeet Year-Round in NZ has the detail on carrying it through winter.
What's still cropping
May's harvest is short and firmly at the tail of the season:
- Beans (climbing), lettuce and peas all reach the end of their harvest windows this month — clear the last of them and free up the beds.
- Radish carries on through June, quick to pull as it sizes.
- Pumpkin runs to June; leave the fruit until the skin won't dent under a thumbnail, then cure it in the sun before it goes into store.
- Jerusalem artichoke keeps going to August. The winter cold works in its favour — dig tubers as you want them and leave the rest in the ground.
Timing notes for cool/mountain gardens
May is a deadline month at one end and an opening at the other. Get garlic and the last root and leaf sowings in early while there's a little warmth left in the soil to help germination; leave it to the cold weeks and the autumn sowings simply won't establish.
As the summer beds empty, clear the spent plants and mulch the bare soil rather than leaving it open to winter rain — it holds the soil structure and keeps weeds down until spring.
Recommended cultivars
- Garlic: Rocombole Early Red (Koanga Institute) on 10–12.5cm diagonal spacings, or Elephant (Koanga Institute) at 15cm where you want larger cloves — snap Elephant's flower heads off young so the plant feeds the bulb rather than the flower.
- Beetroot: Bulls Blood (Kings Seeds NZ) or Bull's Blood (Koanga Institute), a dark-leaved beet comfortable with a late, cool sowing.
- Carrot: Amsterdam Sprint (Kings Seeds NZ), the safer, faster pick this late in the window; Akaroa Long Red (Koanga Institute) where the soil is deep and stone-free enough to suit a long root.
- Silverbeet: Ford Hook Giant (Kings Seeds NZ) for volume of leaf, or Bright Yellow (Kings Seeds NZ) if you'd like brighter stems in the winter bed.
Know your zone? Explore the full NZ Cool/Mountain Planting Calendar for month-by-month sowing and harvest timing.