1. Introduction to lighting

Lighting is a crucial factor for successful indoor cannabis cultivation. It has a significant impact on the growth, health and yield of your plants. In this section, you will learn why lighting is so important and what basics you should know to achieve optimal results.

Importance of lighting for cannabis cultivation

In indoor cultivation, artificial lighting replaces natural sunlight, which is essential for photosynthesis and therefore plant growth. Without sufficient light, your cannabis plants cannot produce the energy needed to grow healthily and develop high-quality flowers. Here are the main reasons why lighting is so important:

• Photosynthesis:Light is the energy source for photosynthesis, the process by which plants convert light into chemical energy to grow and develop.
• Growth phases:Different light cycles and spectra are necessary to optimally support the various growth phases – from germination through the vegetative phase to flowering.
• Yield quality:Optimal lighting promotes the development of dense and resin-rich flowers, resulting in higher yields and better quality.

Basics of light intensity and spectra

To use lighting effectively, it is important to understand the basics of light intensity and light spectra.

Light intensity

Light intensity, measured in lumens or PAR (Photosynthetically Active Radiation), indicates how much light a light source emits. High light intensity is crucial for the growth and development of your plants. Here are some important terms you should know:

• Lumens:A measure of the brightness of the light. The higher the lumen value, the brighter the light source.
• PAR (Photosynthetically Active Radiation):The amount of light used by plants for photosynthesis. PAR measures the intensity of light in the range of 400 to 700 nanometers, which represents the range of the light spectrum usable by plants.
• PPF (Photosynthetic Photon Flux):The number of photons in the PAR range emitted per second by the light source. Measured in micromoles per second (µmol/s).

Light spectra

The light spectrum describes the distribution of the different wavelengths of light. Different wavelengths are important for different growth phases:

• Blue light (400-500 nm):Promotes vegetative growth, strengthens root development and ensures compact plants.
• Red light (600-700 nm):Promotes flowering and fruit formation, increases flower density and size.
• Full spectrum:Contains all necessary wavelengths for all growth phases and best imitates natural sunlight.

Legal aspects in Germany

The cultivation of cannabis in Germany is subject to the Cannabis Act (CanG). It is permitted to grow up to three plants legally. Make sure that your cultivation complies with the legal regulations and that you have all the necessary permits.

Further information on the legal situation can be found in the chapterLegal situation.

With the right understanding of lighting and the use of appropriate techniques, you can maximize the growth and yields of your cannabis plants. Use the other chapters of our grow guide to get detailed instructions and tips and to deepen your knowledge.

4. Light cycles and growth phases

Light cycles play a crucial role in cannabis cultivation and significantly influence the different growth phases of your plants. By adjusting the light cycles to the needs of your plants, you can ensure optimal growth and high yields. In this section, you will learn which light cycles are important in the different growth phases and how to use them effectively.

Light cycles for germination

Germination is the first and one of the most delicate phases in the life of your cannabis plants. During this phase, the seeds need consistent conditions to germinate successfully and develop strong seedlings.

• Light duration:During germination, a constant light source is important. An 18/6 light cycle (18 hours light, 6 hours dark) is often recommended.
• Light intensity:Use moderate light intensity to avoid burning the seeds but provide enough light for photosynthesis.

Light cycles for the vegetative phase

During the vegetative phase, cannabis plants focus on growing leaves, stems and roots. This phase requires longer light cycles to promote vegetative growth.

• Light duration:An 18/6 light cycle is also recommended during the vegetative phase. Some growers even use a 24/0 light cycle (24 hours of light) to maximize growth.
• Light intensity:Increase the light intensity compared to the germination phase to encourage vigorous growth. LEDs and MH (metal halide) lamps are ideal for this phase.
• Light spectrum:A higher proportion of blue light (400-500 nm) promotes vegetative growth and ensures compact and bushy plants.

Light cycles for the flowering phase

The flowering phase is the crucial period in which your plants form flowers and mature. To promote flowering, specific light cycles and spectra are required.

• Light duration:A 12/12 light cycle (12 hours light, 12 hours dark) is necessary to initiate and maintain flowering. The darkness must be absolute, as even small light leaks can disrupt the flowering process.
• Light intensity:High light intensity is particularly important during the flowering phase to encourage the development of large and dense flowers. HPS lamps (high-pressure sodium lamps) and powerful LEDs are ideal.
• Light spectrum:A higher proportion of red light (600-700 nm) promotes flowering and fruit formation. Full-spectrum LEDs can also be used as they cover all necessary wavelengths.

Optimal light cycles

Light cycles play a crucial role in cannabis cultivation and significantly influence the different growth phases of your plants. By adjusting the light cycles to the needs of your plants, you can ensure optimal growth and high yields. In this section, you will learn which light cycles are important in the different growth phases and how to use them effectively.