Indoor Grow Lamps for Beginners

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Hey Nico!
I had a question about indoor grow ops. I have been an outdoor man for a couple years because it’s easy to grow and can produce plenty of flower. I am now starting an indoor op, and I am doing some research before I break ground. I understand the light schedule, but what I don’t understand is what kind of light I should be using during veg and flower stages? I am looking for a lighting system that does not drive my energy bill sky high, but something that is also going to produce a good amount of flower on my plant. Thank you, Nico!
Brandon B. via the mailbag at

Greetings, Brandon!

Thanks for reading and writing in with a question.

Your question regarding horticultural lighting is often daunting to those new to indoor botany. It is understandable, however, as there are now an absolutely ridiculous amount of grow products on the market today. However, it doesn’t have to be so frustrating, as it is actually quite simple when you break it all down.

Let’s first start with the lighting schedule you mentioned, as some folks may not be quite as familiar with light cycles for cannabis plants as you are.

Cannabis is in a class of flowering plants known as angiosperms. These plants produce fruit with seeds, but of course we strive to keep seeds out of our cannabis flowers as it lowers potency and creates a harsher smoke. This is why we cull out males from our gardens, which produce pollen that can pollinate our female plants and create seeds in our buds. Cannabis is also a plant that depends on photoperiodism for its life cycle. Photoperiodism is a physiological reaction to the length of day or night.

For cannabis, it is the daytime photoperiod that is responsible for triggering the flowering phase of the plant’s life cycle. To put it simply, a photoperiod or light cycle of more than 12 hours will keep a cannabis plant in its vegetative state, growing strong and robust. Once the light cycle drops below 12 hours, the flowering stage of growth is induced.

Of course, indoor growers can control the photoperiod simply by putting their grow lamps on timers. Most indoor growers will “veg” young seedlings or clones for anywhere from two weeks to two months. Anything longer will create plants that are unruly and typically too large for indoor grow spaces. It is important to remember that once the vegetative stage ends, the flowering stage will still add anywhere from 30-50 percent more growth to the plants.

The vegetative stage is important because it ultimately dictates the final size (and yield) of your plants. It is for this reason that growers will utilize metal-halide (MH) bulbs during the vegetative phase, as these bulbs are heavier in the blue spectrum of light. Blue wavelengths of light will help keep plants from stretching, keeping them shorter and squatter. This produces plants that are bushier, with shorter internodal lengths (the distance between branches on the main stem). This in turn helps save space indoors, but also produces more budding sites which typically occur at the nodes where branches meet a stem. This then helps to increase yield as well.

Once you change your photoperiod to 12 hours light/12 hours dark per day, the flowering stage will be triggered.

During this stage, indoor growers will change over to high-pressure sodium bulbs (HPS). These bulbs are heavier in the red spectrum of light which mimics more closely the autumn sun.

However, truth be told, many growers will utilize a combination of both MH and HPS bulbs in their flowering rooms nowadays in order to create a broader, full spectrum light for plants. This is actually a great idea, as the blue wavelengths of spectrum—which are the shorter wavelengths—carry with them higher concentrations of light energy (in the form of photons). The added light energy is an excellent way to boost photosynthesis during the flowering stage when plants need all the energy they can produce to add yield and potency to your harvest.

It should also be noted that newer, ceramic discharge lamps (CDLs) have now become part of this conversation, too.

MH and HPS bulbs fall under the category of high-intensity discharge (HID) lamps. These lamps are necessary to supply the high amount of light energy needed for indoor horticultural. CDLs are along the same vein in this regard, however, they utilize a ceramic base and are more energy efficient at 315 watts. They are manufactured to be heavy in both the blue and red spectrums, but produce a full-spectrum white light as the sun does. These lamps tested extremely well in the High Times lighting trials conducted last year. Long-time HIGH TIMES contributors Mel Frank and Harry Resin, as well as myself, are big fans of these lamps from Boulder Lamp.

Lastly, it is important to note that indoor plants crave the same light our outdoor plants receive, which is to say sunlight. Sunlight is full-spectrum, white light. Plants have evolved for millions of years to develop most efficiently under this type of light.

The broader spectrum you can feed your plants, the better light nutrition and overall health they will have. Many growers ask about short-spectrum lighting, lamps that produce only blue or red spectrums, for example. These lamps do have applications for indoor horticultural, but they are best used to supplement our HID lamps to help boost yield or areas of deficiency in indoor operations.

Thanks for reading everyone and remember: Grow… And help the world grow, too!

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