Short answer: December opens no new sowing windows in cool/mountain gardens — everything sowable now has been open since October or November. What's new is harvest: garlic, broccoli, carrot, peas and broad beans all come into cropping for the first time this month, alongside seven crops already underway.

The cool/mountain December context

The frost period ran March through November, so by December the zone is fully frost-clear — the same as every other NZ zone at this point in the year. That's why nothing new opens this month: the frost-tender crops that were waiting on clear ground (courgette, pumpkin, climbing beans, the perennial tubers) already started sowing in November, and everything else has been open since spring.

Where this zone genuinely differs is at the far end of the season, not the near end. Autumn frost returns here as early as March — a month or more before it does in warmer NZ zones — so several crops sown earlier this year are working a shorter runway than their counterparts elsewhere: basil, courgette and tomato all close their harvest windows in March here rather than April, and yacon manages only a single harvest month (March) instead of two. None of that changes what to plant this month, but it's worth knowing while you're planning succession sowings into December and January.

Garlic: the headline difference this month

This is the one crop where cool/mountain gardens are doing something genuinely different in December, not just running a shorter season. Garlic here is planted latest of the three NZ zones — cloves go in near the June winter solstice, because hardneck garlic needs an extended stretch of cold below 10°C to trigger clove formation, and this zone reliably delivers it. That later planting pushes the harvest later too: December through January, roughly seven months after planting.

The practical upshot: if you're used to reading a generic NZ gardening calendar (or a temperate-zone one), don't lift your garlic early. In warmer zones December is when garlic's harvest window is closing out; here it's just beginning.

What to sow now

Nothing new opens this month, but the full spring-and-summer lineup keeps going. The fruiting crops — courgette, cucumber, peas and pumpkin — stay sowable, alongside climbing beans and basil. Roots (beetroot, carrot, radish) and leafy greens (lettuce, pak choy, silverbeet, spinach) round out the list, all still within their earlier-opened windows. Radish, lettuce, pak choy and spinach are quick enough to be worth succession sowing into any space that opens up as earlier crops finish.

Last call: Jerusalem artichoke, mizuna and yacon

Two of the remaining plantings go in as tuber pieces or crown divisions rather than seed — Jerusalem artichoke and yacon — and December is the final month for both. Koanga Institute is the only supplier with any record of either crop, so treat the window edges as a frost-anchored estimate rather than a precise cutoff. Mizuna's seed-sowing window shuts too, having run since August; Egmont's catalogue lists a second run in February–March for anyone who misses this one.

Transplant now

Basil and cucumber, both transplanting since November, continue through to February. Tomato (transplanting since October) and broccoli (since September) both close their transplant windows this month — if you've still got seedlings in trays, get them into the ground now rather than holding them into January.

Harvest now

December's big shift is the four crops joining garlic (see above) in the harvest basket for the first time: broccoli heads from the August–November sowing (central head first, then side shoots — net against white butterfly), carrot and peas pulling their first roots and pods from earlier sowings, and broad beans cropping from an autumn sowing through to February.

Everything else keeps ticking along at a steady clip. Beetroot, coriander, kale, lettuce, mizuna, pak choy, radish, silverbeet and spinach have all been in harvest since earlier months and need nothing new beyond regular picking. Growing Silverbeet Year-Round in NZ has tips for keeping it productive well past this point.

Mustard greens close out their harvest window at the end of December — the last of the October transplant.

Recommended cultivars

  • Basil: Cinnamon (Kings Seeds NZ); or Genovese (Koanga Institute), planted out at 30cm once the ground reaches 15°C.
  • Climbing Beans: Anasazi (Kings Seeds NZ), direct sown; or America (Koanga Institute), tray-raised and transplanted under trellis to dodge birds, slugs and cold-ground rot.
  • Beetroot: Bulls Blood (Kings Seeds NZ), direct sown.
  • Carrot: Amsterdam Sprint (Kings Seeds NZ); or Akaroa Long Red (Koanga Institute), a direct-scatter strip sowing.
  • Courgette: Black Beauty (Kings Seeds NZ).
  • Cucumber: Amira F1 or Crunchy F1 (both Kings Seeds NZ), tray-raised transplants.
  • Lettuce: Buttercrunch or Coral Red (both Kings Seeds NZ).
  • Peas: Alderman Tall Climbing (Kings Seeds NZ), direct sown; or Amish Snap (Koanga Institute), tray-raised under a 1.6m trellis.
  • Pumpkin: Atlantic Giant (Kings Seeds NZ); or Austrian Hulless (Koanga Institute), transplanted at 1m spacing once soil hits 15–16°C.
  • Spinach: Bloomsdale (Kings Seeds NZ); or Japanese/Lands End (Koanga Institute), sown after peas or beans for the most delicately flavoured leaves.
  • Jerusalem artichoke, mizuna, pak choy, radish and yacon carry no zone-specific cultivar notes yet — choose an NZ-suited variety from your usual supplier.

Know your zone? Explore the full NZ Cool/Mountain Planting Calendar for month-by-month sowing and harvest timing.