Lighting Configuration for Indoor Growing: Hanging Heights
Lighting Configuration for Indoor Growing
Light drives growth. Get spectrum, intensity and hanging height right and you’ll see stronger roots, tighter internodes and bigger yields. Below we cover classic options (T5, Eco-Light, 600W HID) and add modern LED grow light guidance — including heights, dimming and replacement advice.
Choosing a Lamp
Plants respond to wavelengths in the PAR range (400–700 nm). Dual‑spectrum lamps balance blue (veg) and red (flower). Full‑spectrum LEDs deliver a white base spectrum with added deep‑red for flowering efficiency.
| Lamp / Fixture | Spectrum | Best For | Replace / Service |
|---|---|---|---|
| Gavita Lamps | Dual spectrum | Veg & Flower | Every 8–12 months |
| Philips GreenPower | Dual spectrum | Veg & Flower | Every 6–9 months |
| BAY6 / GroLux / Sunmaster | Dual spectrum | Veg & Flower | 5–12 months (model dependent) |
| Osram (Orange/Red) | Red‑biased | Flowering | Every 6 months |
| Metal Halide | Blue | Vegetative | Every 9 months |
| LED Bar Fixtures (modern full‑spectrum) | White + deep‑red | Veg & Flower (full cycle) | No lamp swaps. Clean bars & drivers, expect long service life; check output and dimming yearly. |
Lamp Heights (Legacy Options)
Lower‑intensity fluorescents can sit close above plants. Higher‑intensity HID needs more clearance. Raise lights as plants grow to hold a safe gap.
T5 Single Tube Light
- Ideal height: Directly above cuttings/seedlings in a propagator.
- Why: 24 W tubes run cool; perfect for rooting and early propagation.
Eco‑Light (CFL)
- Ideal height: ~80 cm above seedlings in a propagator; ~60 cm when used as a supplementary lamp.
- Notes: Blue for veg, red for flowering; great as a helper lamp.
600w HID
- Ideal height: ~150 cm above small plants (250/400 W only), ~120 cm for mid‑sized, ~60 cm above large plants.
- Notes: High output. Needs a ballast and good extraction.
LED Grow Lights: Heights, Dimming & PPFD Targets
Modern LED bar fixtures deliver high, even PPFD with less radiant heat than HID. That means you can work a little closer to the canopy — but intensity still matters. Use dimming and height together to hit sensible PPFD targets for each stage.
PPFD targets (no added CO₂):
- Propagation / early veg: 200–400 µmol·m⁻²·s⁻¹
- Veg / pre‑flower: 400–700 µmol·m⁻²·s⁻¹
- Flower (weeks 3–7): 700–900 µmol·m⁻²·s⁻¹ (up to ~1,000 with excellent climate)
Running CO₂? You can push higher PPFD, but only with tight control of temperature, RH and VPD.
Typical LED Heights & Dimming (Guidelines)
Always check your fixture’s PPFD map and use a meter if you have one. If not, these starting points work well for most bar‑style LEDs:
| Fixture Class | Propagation | Vegetative | Early Flower | Late Flower |
|---|---|---|---|---|
| 200–300 W LED (0.8–1.0 m²) | 80–100 cm at 20–35% | 50–70 cm at 35–60% | 40–55 cm at 60–75% | 35–45 cm at 70–90% |
| 450 W LED (1.2 m²) | 90–110 cm at 20–30% | 55–70 cm at 40–60% | 45–60 cm at 60–80% | 35–45 cm at 80–100% |
| 600 W LED (1.2–1.5 m²) | 90–110 cm at 25–40% | 55–70 cm at 40–70% | 40–55 cm at 60–85% | 30–45 cm at 80–100% |
| 800–1000 W LED (2.4 × 1.2 m) | 100–120 cm at 25–40% | 60–80 cm at 50–70% | 45–60 cm at 70–90% | 35–50 cm at 90–100% |
Quick checks: If leaves are tacoing or bleaching, you’re too close or too bright — raise or dim. If plants are stretching, lower or increase intensity. Keep fixtures clean; dust can knock output down.
Replacement & Maintenance
- HID / Fluorescent: Lamps degrade with hours used; replace on schedule (see table) to keep output consistent.
- LED: No lamp swaps. Clean bars, drivers and fans (if fitted), check dimmer accuracy yearly, and keep an eye on room temps — LEDs still add heat to the air.
Final Thoughts
Pick a spectrum that suits your stage, set safe heights, and tune intensity to PPFD targets. With LEDs, use dimming and height together — small tweaks each week keep the canopy right in the sweet spot.
