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Light requirements

How much light does Bok Choy 'Black Summer' (Brassica rapa var. chinensis 'Black Summer') need?

Also called Black Summer bok choy, dark bok choy.

More about bok choy 'black summer'

About Bok Choy 'Black Summer'

Brassica rapa var. chinensis 'Black Summer' · also called Black Summer bok choy, dark bok choy · edible

'Black Summer' is a fast, uniform bok choy with very dark green leaves and crisp pale stalks, bred for slow bolting and heat tolerance so it crops reliably through warmer weather. A cool-season Asian green, it matures in roughly six to eight weeks and is ideal for successional sowing in spring, summer, and autumn for stir-fries and steaming.

Comfort temperature: 13-24°C

The exact light bok choy 'black summer' needs

Bok Choy 'Black Summer' is a sun-driven crop — yield is directly limited by how much direct sun it gets, so this is one plant where "more light, more harvest" is literally true.

Put a number on it — this is what a meter (or a free phone light-meter app) should read where bok choy 'black summer' sits:

In plain terms, Full sun outdoors: an open spot that gets 6–8 hours of unobstructed direct sun, ideally including midday. Indoors or on a windowsill it needs the brightest south-facing position you have and usually still benefits from a grow light. Shaded beds, north-facing walls, and gappy "dappled" light — these grow lush leaves but little or poor-quality crop.

Not sure how to read the light in your home? Our light meter guide walks through measuring footcandles and lux with a free phone app and turning the reading into a placement decision for bok choy 'black summer'.

Signs bok choy 'black summer' is getting too much light

The most exposed leaves show it first. For bok choy 'black summer' specifically, watch for:

Light damage does not heal — a scorched leaf stays scorched — so the fix is to move bok choy 'black summer' out of the harsh light rather than wait for it to recover.

Signs bok choy 'black summer' is not getting enough light

Too little light is slower and sneakier than too much. The classic tell is etiolation: the plant stretches and pales as it reaches for a window. For bok choy 'black summer', look for:

If bok choy 'black summer' is stretched, leggy and pale, our guide to leggy, stretched plants covers how to fix it and whether it can be pruned back into shape. Tucking bok choy 'black summer' into a part-shade corner and expecting a full crop. Leafy growth tolerates some shade, but fruit, roots and flavour are paid for in hours of direct sun — short the light and you short the harvest.

Where to put bok choy 'black summer': the best window and room

Give bok choy 'black summer' the sunniest open ground or the largest container in the brightest spot you have. A south-facing wall, allotment in the open, or unshaded raised bed is ideal. If you are growing it indoors or on a balcony, a full-spectrum grow light is usually not optional but essential — a windowsill alone rarely ripens a sun crop well.

  1. Pick the sunniest position. Site bok choy 'black summer' where it gets 6–8 hours of direct sun — open ground or the brightest container spot, away from walls and tree shade.
  2. Track the sun across the season. A spot sunny in May can be shaded by a leafed-out tree or low autumn sun later. Watch where the shadows actually fall before committing.
  3. Add a grow light indoors. Growing bok choy 'black summer' inside or on a windowsill? Run a strong full-spectrum LED 12–16 hours a day — windowsill light alone rarely crops well.
  4. Mulch and water to handle the heat. Full sun comes with heat stress; mulch and consistent watering prevent the scorch and bolting that sun gets blamed for.

Does bok choy 'black summer' need a grow light?

For indoor or windowsill growing, bok choy 'black summer' almost always needs a grow light to crop properly: a strong full-spectrum LED run 12–16 hours a day, positioned close. Light is the single biggest limiting factor for a sun crop grown inside — soil and water can be perfect and it will still fail in dim light.

The seasonal light shift (why winter changes everything)

Bok Choy 'Black Summer' is a growing-season crop. Outdoors, plant it so its main growth lands in the long, high-sun months — light and warmth fall away fast from autumn. For year-round indoor growing you must replace the lost winter sun with a grow light on a timer; the natural window light from October to February is far too weak for cropping.

Light and watering are linked: a plant in weaker winter light photosynthesises and drinks far less, so the same routine that worked in summer can rot it. See how often to water bok choy 'black summer' for the season-by-season schedule that pairs with this light plan.

Bok Choy 'Black Summer' light requirements — frequently asked questions

How much light does bok choy 'black summer' need?

Bok Choy 'Black Summer' needs Outdoor full sun is ~5,000–10,000+ fc; far beyond anything a windowsill provides. Tens of thousands of lux in open sun — orders of magnitude more than typical indoor light. Full sun outdoors: an open spot that gets 6–8 hours of unobstructed direct sun, ideally including midday. Indoors or on a windowsill it needs the brightest south-facing position you have and usually still benefits from a grow light.

Can bok choy 'black summer' survive in low light?

No, not really. Bok Choy 'Black Summer' is a sun lover — in low light it etiolates: it stretches, pales, weakens and slows right down. It will not instantly die, but it steadily declines and never looks its best.

What are the signs bok choy 'black summer' is getting too much light?

In extreme heat plus intense sun, leaf scorch or sunscald on exposed fruit — usually a heat/water-stress combination rather than light alone; mulch and steady watering fix most of it. Wilting in the fiercest afternoon sun that recovers by evening — bok choy 'black summer' is photosynthesising hard, not over-lit; keep it watered. Bolting (premature flowering) in leafy crops is triggered more by heat and daylength than raw light intensity. Tucking bok choy 'black summer' into a part-shade corner and expecting a full crop. Leafy growth tolerates some shade, but fruit, roots and flavour are paid for in hours of direct sun — short the light and you short the harvest.

What are the signs bok choy 'black summer' is not getting enough light?

Tall, pale, leggy, floppy bok choy 'black summer' reaching for the light, with thin stems that flop — classic shade etiolation. Poor flowering and a small, late, disappointing or non-existent harvest — the clearest sign it is under-lit. Lush dark leaves but few fruit; soft growth that pests and disease find easily. If you see this, move bok choy 'black summer' closer to the light or add a grow light — and check our guide on leggy, stretched plants.

Does bok choy 'black summer' need a grow light?

For indoor or windowsill growing, bok choy 'black summer' almost always needs a grow light to crop properly: a strong full-spectrum LED run 12–16 hours a day, positioned close. Light is the single biggest limiting factor for a sun crop grown inside — soil and water can be perfect and it will still fail in dim light.

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