The Ultimate Guide to Healthy Growth
Light is the engine of life – and in cannabis cultivation it’s the most important factor for the quality and quantity of your harvest. Without the right lighting, even the best nutrients are useless. But the world of grow lamps is complex: from classic HPS to the latest LED technology, the differences are huge.
In this article on weedx.ch we explain what really matters so your plants are bursting with energy. The basics apply to plants from seed as well as to hemp clones.
Why not all light is equal
Cannabis plants use light for photosynthesis, but they “see” light differently from us. While we pay attention to brightness (lumens), two other values count for the plant:
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PAR (Photosynthetically Active Radiation): the part of the light spectrum (400–700 nm) that plants can actually use for growth.
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PPFD (Photosynthetic Photon Flux Density): this value measures how many light particles (photons) actually reach the leaf surface.
The different lamp types compared
1. LED grow lights (today’s standard)
LEDs have revolutionised the market. They cost more to buy, but offer unbeatable advantages.
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Pros: low power consumption, very little heat, long lifespan and often an adjustable light spectrum (full spectrum).
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Ideal for: growers looking for efficiency and discretion (less waste heat).
2. HPS (high-pressure sodium lamps)
The “old school” of growing. HPS lamps have a very strong red/yellow spectrum, which makes them excellent for the flowering phase.
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Pros: cheap to buy, enormous light intensity.
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Cons: get extremely hot (fire risk/cooling needed), high power consumption.
3. CMH / LEC (ceramic metal halide)
A good middle ground with a light spectrum very close to natural sunlight.
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Pros: excellent UV output, which can boost resin production.
The right spectrum for every phase
Your plants need different “light colours” depending on their stage of life:
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Growth phase (vegetative): here cannabis prefers blue light (approx. 400–500 nm). It ensures compact growth, strong stems and healthy leaves.
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Flowering phase: now the plant craves red light (approx. 600–700 nm). This spectrum simulates the low autumn sun and stimulates flower formation.
Pro tip: the right distance
A common mistake is the wrong distance between the lamp and the top of the plant.
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Too close: light burn (bleached tips) or heat stress.
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Too far: the plants stretch (they grow tall and unstable in search of light).
Rule of thumb for LEDs: 30 to 50 cm is usually ideal, but always check the manufacturer’s specifications for your model.
Conclusion: invest in the future of your buds
Lighting is the heart of your indoor grow. While beginners often start with cheap HPS lamps, in the long run there’s no way around high-quality LEDs if you want to cut electricity costs and maximise terpene quality.
Quality at weedx.ch: a perfect light spectrum creates the resin crystals that make our products so special. Discover first-class CBD products and CBD flowers at weedx.ch, grown for you under optimal lighting conditions!
Sources & further reading
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University of Utah: Crop Physiology Laboratory – light studies on cannabis. (Scientific data on photon flux.)
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Royal Queen Seeds: LED vs HPS: which lighting is better?
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Canna: The influence of light on plant development.
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Grow Weed Easy: The complete guide to cannabis grow lights.
