Everything you need to know about LED grow lights
Grow lamp: The heart of successful indoor cultivation of hemp & co.
The right grow light is essential if you want to cultivate hemp , cannabis plants , or other light-loving plants indoors—whether in a grow box , tent, or greenhouse. Without optimal light, there's no growth, no flowering, and no harvest. If you want long-term, healthy plants and abundant yields, you can't do without a high-quality grow light .
Modern LED grow lights set new standards here. They consume significantly less power and deliver a perfect light spectrum for every growth phase – from germination through vegetation to flowering. Compared to outdated light sources such as incandescent or sodium vapor lamps, the light output of LED technology is unbeatable: Up to 85% of the energy is efficiently converted into plant-usable light.
A powerful grow light is crucial, especially for growing hemp or cannabis plants. High-quality models offer a sun-like spectrum with UV and infrared components – ideal for vibrant plants, dense buds, and maximum resin production. At the same time, a modern grow light can reduce your energy costs by up to 60% .
Another advantage: ease of use. Our LED grow lights are true plug-and-play solutions. No tinkering, no complicated wiring, no additional accessories – just unpack, plug in, and get started. Indoor growing can be that simple today.
How a grow lamp with LED technology works
Modern grow lights are based on powerful LEDs – so-called light-emitting diodes. These small diodes consist of a semiconductor that emits light as soon as current flows. Plastic lenses or glass covers are often placed over the semiconductor. Some models also use reflectors to direct the light more precisely onto your cannabis plants or other crops.
The biggest advantage of an LED grow light is its adjustable light spectrum. While older light sources like high-pressure sodium lamps only provide a limited color spectrum, LEDs can be combined to create a broad or plant-specific spectrum—ideal for your cannabis plant's needs, from germination to flowering.
This means that a modern plant lamp can be precisely tailored to the respective growth or flowering phase of your cannabis plants – for healthy development and maximum harvest.
Which grow lamp is suitable for which area?
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60 × 60 cm
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90 × 90 cm
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120 × 120 cm
There's a suitable grow light for every space. And if you want to keep things simple, we also offer fully equipped grow boxes (complete sets) with integrated LED plant lights – perfect for beginners and professionals.
What light your cannabis plant really needs in each phase
Lighting during the growth phase
- A grow lamp with a blue color spectrum is crucial for the growth phase.
- The optimal light spectrum is around 4000–8000 Kelvin.
- Most effective: plant lamps with 5000–7000 Kelvin.
- Ideal for healthy hemp plants and strong vegetative development.
Secret Jardin Cosmorrow LED 20 W 50 cm Grow PPE 2.7
The Cosmorrow LED 20 W grow lamp is designed for the growth phase of your plants.
Lighting during the flowering phase
- To flower, your cannabis plants need light in the red color spectrum.
- Grow lamps with 2500–3500 Kelvin are optimal.
- In addition, infrared light (approx. 730 nm) promotes flower formation.
- Modern full-spectrum LEDs therefore often integrate infrared LEDs for better yields and terpene production.
Secret Jardin Cosmorrow LED 40 W 90 cm BLOOM PPE 1.8
The Cosmorrow LED BLOOM with its red peak of 660 nm is designed for the flowering phase.
What are full spectrum LEDs?
- Full-spectrum grow lamps cover the entire required light spectrum – from germination to flowering.
- The spectrum usually ranges from 400 to 780 nm – including UV and far-red ranges.
- For LEDs, color specifications are often given in nanometers (nm) instead of Kelvin.
- High-end models even contain additional UV-A light.
Secret Jardin Cosmorrow LED 20W 50cm Full Spectrum
This waterproof LED grow light is specially designed for the growth and flowering phase .
The best lamps for growing
- Special LED plant lamps for young plants and cuttings are particularly gentle.
- They produce little heat and avoid hotspots – ideal for sensitive seedlings.
- Recommendation: Cosmorrow LEDs from Secret Jardin – including dual power supply for two light strips.
- Optimal conditions for strong roots and stable cannabis seedlings .
Technical specifications for grow lamps: What really matters
Power (watts)
- The power of a grow lamp is given in watts.
- It serves as a rough guideline but does not replace a detailed assessment.
- Watts alone say little about the actual light output for hemp plants .
Lumen
- Lumen measures the visible luminous flux – important for the human eye, not for plants.
- Grow lights should be optimized for the plant light spectrum (red/blue), not for visual brightness.
- Green light is strongly perceived by the eye, but does little for the cannabis plant .
- Lumen is therefore of limited use when choosing a grow lamp .
PAR value
- PAR (Photosynthetically Active Radiation) indicates how much usable light is emitted for photosynthesis.
- In contrast to lumens, PAR covers the spectral range important for cannabis .
- PAR is more useful for evaluating a plant lamp .
- Important: Here too, factors such as beam angle or measuring height are relevant.
Efficiency
- Efficiency = light output / energy input – measured in µmol/J.
- The higher this value, the more usable light the grow lamp produces per watt of electricity.
- In plant lighting, wavelengths between 400–700 nm (PAR range) are particularly important.
- Modern LEDs now also cover UV and far red (380–780 nm).
Module efficiency
- Refers only to the LED light source itself – without loss due to driver, reflector, etc.
- Example: A sodium vapor lamp with 1.7 µmol/J produces at 600W = 1020 µmol/s.
System efficiency
- Including all components: lamp, driver, reflector, cover, etc.
- Calculation example for 600W sodium vapor lamp:
- Module: 1.7 µmol/J
- Ballast: 94% efficiency
- Reflector: 85% efficiency
- System efficiency: 1.7 x 0.94 x 0.85 = 1.358 µmol/J
- Output at 638W: 638 x 1.358 = 866 µmol/s
- Modern LED grow lamps often achieve significantly higher system values.
PPFD (Photosynthetic Photon Flux Density)
- Measures the amount of photons (µmol) hitting the plant per second and square meter.
- An important value for assessing light distribution and intensity.
- Often shown graphically – pay attention to the measurement height and beam angle.
- Grow lamps with high PPFD values bring visible benefits to cannabis cultivation.
| Characteristic | LED grow lamp | High-pressure sodium lamp (HPS) |
|---|---|---|
| System efficiency (µmol/J) | up to 2.7 µmol/J | approx. 1.35 µmol/J |
| life | 50,000 – 100,000 hours | approx. 10,000 – 20,000 hours |
| Light spectrum | Full spectrum (including UV & IR possible) | strong in the red range, hardly any blue component |
| Heat development | small amount | high (additional cooling required) |
| Power consumption | lower with the same light output | higher with comparable output |
| Price (purchase) | higher | cheaper |
| Price (long-term) | more cost-efficient due to lower power consumption & longer service life | more expensive due to replacement lamps & electricity costs |
Conclusion: The right grow lamp makes the difference
Whether it's hemp, cannabis, or other light-loving plants, a suitable grow light is key to healthy growth and a bountiful harvest. Modern LED grow lights not only offer an ideal light spectrum, but also impress with their energy efficiency, long lifespan, and low heat generation. Using a high-quality LED grow light is particularly worthwhile when growing cannabis or hemp plants indoors – both during the growth and flowering phases.
Choosing the right grow light depends on many factors—growing area, plant species, growing goals, and budget. But one thing is certain: investing in quality will reward you with better growth, higher yields, and lower energy consumption.
Tip: When purchasing your grow light , look for tested PAR and PPFD values, a true full spectrum, and a system efficiency of over 2.5 µmol/J – so your cannabis plants get everything they need.