Garlic needs a long, cold spell to split a planted clove into a full bulb — and in cool and mountain New Zealand, that's the one thing you never lack. So when a bulb doesn't form here, the usual national culprit (not enough winter chill) is almost never the reason. In a cold zone, a single undivided "round" is far more likely to be a plant that was lifted too soon, or one that simply ran out of season. Here's how to tell which, and how to get a full bulb next year.

The most common reasons — ranked for cool and mountain gardens

1. Harvested too early. This rises to the top in cold zones, because your season runs late. Cool and mountain garlic is planted latest of all NZ zones and harvests in December–January — so the temptation to lift in November, when warmer regions are already pulling their crop, is exactly what leaves you with an unfinished, undivided bulb. Wait for the leaves.

2. Too short a season for the variety. In the coldest mountain gardens, a late spring and an early autumn can squeeze the growing window. A variety that needs a long run may not finish sizing before the tops die down. Choosing a type suited to a short cool season matters more here than anywhere else.

3. Starved or crowded plants. Garlic is hungry, and cold soils are slow to release nutrients. Poor or unimproved beds, or cloves packed too close, give small single-layer bulbs. Rich, free-draining soil and 10–15cm spacing still apply — arguably more so in a slow-warming bed.

4. Planted too late even for a cold zone. "Plant near the winter solstice" is the cool-zone rule, but there's still a limit — cloves that go in deep into winter may not establish roots before the coldest weeks, costing them vigour later. May into June is the target.

5. Not enough cold. Listed last and, honestly, almost never the problem here — this is the zone that supplies the chilling other regions struggle to get. If your garlic isn't bulbing in a mountain garden, look up this list, not at the thermometer.

Check your timing against the cool/mountain window

The cool and mountain window runs May through June, close to the winter solstice, with harvest in December–January — hardneck garlic uses that extended spell of cold below about 10°C to trigger clove formation, and your zone delivers it in spades. The old adage "plant on the shortest day, harvest on the longest" is a cool-zone rule of thumb for a reason. See the full picture on the NZ Cool/Mountain planting calendar.

What to do now

Leave the bed alone until the lower third to half of the leaves have yellowed — in a cold zone that may be January, later than you'd expect. Dig one plant to check before committing to a full harvest. A round is good eating and even better seed: replant your best ones next autumn and they'll usually bulk up into large bulbs, carrying a full season's stored energy into the ground with them.

What to change next season

  • Hold your nerve on harvest timing — lift in December–January when the leaves say so, not when warmer regions do.
  • Choose a variety suited to a short, cold season.
  • Improve the bed with compost and well-rotted manure before planting, since cold soil is slow to feed the crop.
  • Aim for a May–June planting: late enough to sit through the solstice cold, early enough to establish roots first.

The good news: your zone gives garlic exactly the cold it wants, so once the harvest timing is right, cool and mountain gardens grow some of the best bulbs in the country.

New to garlic timing here? See When to Plant Garlic in Canterbury NZ for a worked cool-zone example, or explore the full NZ Cool/Mountain Planting Calendar →.