Grow Lights Distance Chart UK (2025) | LED, Fluorescent & HPS Guide

Getting the distance right between your plants and their grow lights is one of the most important parts of indoor gardening. Too close, and leaves burn. Too far away, and plants stretch weak and leggy. This guide explains the best grow lights distances for seedlings, vegetative plants, and flowering crops, plus a handy grow lights distance chart for UK growers.

Not quite what you’re looking for? Take a look at our Grow Lights UK – Complete Resource Hub for a full overview of light types, setup tips, and running costs.

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Why Grow Lights Distance Matters

Grow lights provide the intensity and spectrum that plants can’t always get from natural UK daylight — especially in winter. But if grow lights are set at the wrong height:

• Too close: leaves bleach, curl or scorch from heat.
• Too far: seedlings grow thin and spindly, fruiting plants may never ripen.

Correct spacing of grow lights gives:

• Strong seedlings
• Compact leafy growth
• Reliable flowering and fruiting

Grow lights are especially useful for:

• Fresh winter salads grown indoors
• Getting a head start on tomatoes
• Growing herbs and vegetables in low-light kitchens or lofts

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General Grow Lights Distance Guidelines

• LED grow lights: 12–24 inches (30–60 cm), depending on power.
• Fluorescent grow lights (T5/CFL): 2–6 inches (5–15 cm) — cooler so they can sit close.
• HPS grow lights: 24–36 inches (60–90 cm) — very hot, so more clearance needed.

⚠️ Household bulbs are not suitable — they don’t produce the right spectrum or strength for plant growth.

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Grow Lights Distance by Plant Stage

Seedlings

• LED grow lights: 24–30 in (60–75 cm)
• Fluorescent grow lights: 2–4 in (5–10 cm)
• HPS grow lights: not ideal

Vegetative Growth

• LED grow lights: 18–24 in (45–60 cm)
• Fluorescent grow lights: 4–6 in (10–15 cm)
• HPS grow lights: 24–36 in (60–90 cm)

Flowering & Fruiting

• LED grow lights: 12–18 in (30–45 cm)
• Fluorescent grow lights: ~6 in (15 cm)
• HPS grow lights: 18–24 in (45–60 cm)

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LED Grow Lights Distance by Wattage

Not all LED grow lights are equal — distance depends on wattage and power output.

• 100–150W LED grow lights (herbs, seedlings, salad greens)
  • Seedlings: 24–30 in (60–75 cm)
  • Vegetative: 18–24 in (45–60 cm)
  • Flowering: 12–18 in (30–45 cm)
• 300–450W LED grow lights (medium setups)
  • Seedlings: 30 in (75 cm)
  • Vegetative: 20–24 in (50–60 cm)
  • Flowering: 14–18 in (35–45 cm)
• 600–1000W LED grow lights (large/high-output panels)
  • Seedlings: 36 in (90 cm)
  • Vegetative: 24 in (60 cm)
  • Flowering: 18–20 in (45–50 cm)

⚠️ Always check the manufacturer’s leaflet and watch for plant stress, as spectrum, lens angle and heat vary.

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Grow Lights Distance Chart

Plant Stage	LED Grow Lights	Fluorescent Grow Lights	HPS Grow Lights
Seedlings	24–30 in (60–75 cm)	2–4 in (5–10 cm)	Not recommended
Vegetative	18–24 in (45–60 cm)	4–6 in (10–15 cm)	24–36 in (60–90 cm)
Flowering	12–18 in (30–45 cm)	~6 in (15 cm)	18–24 in (45–60 cm)

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Light Spectrum and Grow Lights

Distance is only part of the picture. Plants respond to different wavelengths of light:

• Blue light (400–500 nm): Encourages compact leafy growth in vegetative stage.
• Red light (600–700 nm): Triggers flowering and fruiting.
• Full-spectrum grow lights: Combine both for a balance that mimics sunlight.

This is why modern LED grow lights often blend blue, red, and white diodes in a single fixture.

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Troubleshooting Grow Lights Placement

Too close to plants

• Pale, bleached leaves
• Curled or crispy edges

Too far from plants

• Dark-green but weak foliage
• Long, stretched stems

Heat stress

• Leaves curl upward or dry at the tips

Solution: raise or lower your grow lights gradually and keep observing plant response.

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Tips for Adjusting Grow Lights Height

• Start higher, lower slowly to avoid burning.
• Raise grow lights as plants grow taller (every 1–2 weeks).
• Rotate pots weekly for even coverage.
• Use a PAR/lux meter or phone app for accuracy.

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Conclusion

The correct grow lights distance depends on both plant stage and lamp strength. Use the chart and wattage ranges as a starting point, but always check your manufacturer’s guidance and observe your plants.

For more practical advice, you may also like:

• 🌱 Best Indoor Grow Lights UK Beginners Guide (2025)
• 💡 How to Set Up Grow Lights Indoors
• 🔧 Top 10 Grow Light Stand Systems (2025)

Looking for more self-sufficiency and gardening guides? Visit HomeGrower to explore all our latest indoor and outdoor growing tips.

And for background on grow lights generally, see the Royal Horticultural Society’s website.