A coriander plant that's all thin, pale stem and barely any leaf isn't bolting — it's stretching for light. Not enough brightness, seedlings packed in too close, or a warm growth spurt push the plant into stem instead of leaf, and the result is too weak to stand up on its own. There's no flower stalk involved, which is the tell that separates it from bolting: this is fixed with light, space and steady conditions, not anything you'd do once a plant has already run to seed.

Why it happens, most likely cause first

  1. Not enough light. This is by far the most common cause of a drawn, floppy seedling. Starved of brightness, the plant chases whatever light it can find and spends its energy on height rather than leaf. A tray on an indoor sill through a cool/mountain winter is the textbook setup for this.
  2. Sown too thick. A crowded row or an overfilled cell means every seedling is competing with its neighbours for the same light, so the whole batch draws upward together instead of a few plants filling out properly.
  3. Too warm. Heat pushes a growth spurt where stem outruns leaf. A hot windowsill or an indoor spot that's warmer than the plant wants will exaggerate the stretch.
  4. A mix that dries out or runs thin on nutrients. Without steady moisture and food, seedlings put out weak, skinny growth rather than anything sturdy.

Leggy, or is it actually bolting?

Both end with a taller plant, but they're not the same fault and don't share a fix. Legginess is a soft, pale seedling — stem with barely any leaf on it. Bolting is a firm central stalk carrying flower buds and fine, feathery top growth, driven by heat and day length rather than shade. If you can see buds forming, this isn't your problem — see Why Is My Coriander Bolting Immediately in NZ Cool/Mountain? instead.

What the cool/mountain calendar changes

Coriander's sowing window here runs July through November, with harvest September to January — the same Egmont-sourced dates that apply in every NZ zone, so there's no separate cool/mountain timing to learn. What does change is the light behind that window.

Cool/mountain's frost season runs March to November — starting a full month earlier than the temperate zone's April start — which means the sowing window opens into a longer run of short, dim days than gardeners further north get. That's exactly the setup that produces low-light legginess: it's tempting to get an early start on a windowsill through a long, cool season, and a dim sill in July here is dimmer for longer than the same sill in a temperate garden. This is a read on the local light and frost calendar, not a separately sourced cool/mountain fact — but it's the reason the low-light cause above tends to dominate in this zone specifically, more than the heat-and-crowding version that shows up once summer arrives elsewhere.

Practically: hold off starting coriander early indoors just because the season's short. A late direct sowing into real daylight beats an early one raised thin on a sill.

Fixing a leggy batch now

  • Get it into as much light as you can. A bright, open, full-sun spot is right through winter here (Yates NZ backs full sun over winter, easing only once summer heat lands). If you're raising seed indoors, it needs a genuinely bright sill or a grow light held a few centimetres above the tops — not lighting the room, lighting the plant.
  • Thin ruthlessly and early. Space seed out to start with, then thin while seedlings are still small so each one gets room instead of a crowded, shading mat. The thinnings are edible as micro-leaf, so nothing's wasted.
  • Sow direct rather than nurse it indoors. Coriander runs a long taproot and hates being moved, so a bright bed sown straight avoids both the dim windowsill and root disturbance in one move. Don't try to bury the stem deeper to fix it — that's a tomato trick, and coriander won't root along a buried stem.
  • Keep the mix cool, even and moist. A hot corner and a mix that swings from dry to soaked both push the plant toward soft, drawn growth.
  • Run a hand or a fan over the seedlings daily. Mimicking wind movement thickens stems faster than still air ever will.
  • Watch for damping off. Thin, crowded seedlings collapse easily, so keep air moving and don't overwater a batch that's already stretched and soft.

Next season

Once the days lengthen, sow direct into open ground in short, thin successions rather than one dense patch. Kings Seeds NZ's Picante is a direct-sown pick suited to that approach; Koanga's heritage NZH is raised in trays and pricked out young, so if you're growing that one, get the seedlings under strong light and moved on while still small. A batch that's already badly drawn rarely turns back into something sturdy — coriander is quick, so treat it as a fast reset and re-sow into better light rather than nursing it along.

More on this zone: see the full NZ Cool/Mountain Planting Calendar →.