The most common mistake beginners make is going cheap on the grow light.
How the light spectrum affects plantsWhen we talk about the light spectrum, we're talking about the ratio of red, blue, and UV-B (Ultra Violet) light. So the main thing to remember is the means by which each spectrum impacts your plants.
- Red light promotes flowering and vertical plant growth. An excess of red light too early will make your plants stretch, which translates to lower yields and weak, wobbly plants.
- Blue light is important in every phase of growth, but is the predominant light needed during the seedling/cloning and vegetative phases to ensure a strong plant. Blue light is also responsible for ramping up oil and resin production.
- UV-B light favorably stresses your plants. Just like people, plants effectively shield themselves from the sun's UV-B rays. However, rather than sunblock, they produce more trichomes, which strengthen potency, flavor, and aroma of the plant and it's fruit.
- Green light is almost undetectable by plants. Chlorophyll diffusively reflects the green spectrum of light, giving plants their green color. Plants actually take their cues on when to grow, when to flower, etc. from the length of the night, or the dark intervals on your grow light. Use low power green light for illumination if you need to move around your grow room after your plants go to sleep (the dark interval). It will not confuse the plant like white light.
When to use which color spectrum.The spectrum of light you expose your plants to tells them when to enter each phase of growth by guiding them through the seasons. If you grow indoors, you have to completely recreate all the phases of the sun for your plants through your use of grow lights.
Here’s what a typical growth cycle should look like:
SeedlingsWhen starting from seeds, you want to give your seedlings 24-hours of low intensity light. Ideally, you want about 15% red and 30% blue and white. When your seedlings get their first set of true leaves, you can double the intensity until they have more than two sets of leaves, at which point they’ve reached the vegetative stage.
ClonesWhen starting with clones, your primary goal is to promote rooting. This takes some effort on your plants’ part, so keep the light intensity low. You want about 25% red and 45% blue and white light. This helps the plants focus energy on deepening roots rather than growing upward.
Vegetative StageIn the veg stage, your plants should focus on root growth and developing tight internodes. A healthy dose of blue light is your best bet. Higher concentrations of blue keep plants a little shorter and they develop stronger stems to support later growth. You don’t want your plants to get too tall, develop longer internodes, and create a situation in the flowering stage where taller leaves form a canopy that blocks light to the buds that grow lower on the plant. Turn your blue and white light levels to 100% and maintain red at less than 60%.
Pre-Flower StageThis is when you should start prioritizing bud growth. Remember, red-light signals the plant to start flowering. Increasing your red light will get your plants to start budding. However, you still avoid giving your plants in too much red. Red light also promotes vertical growth, and you want to avoid flowering stretch at this stage. At pre-flower, your wisest move is to kick the intensity of red light up just a little, to about 80%. Your blue light concentration can remain right where it was.
Flowering StageNow is the red spectrum’s turn. You’ve been limiting red light to prevent stretching, but now your plant needs all the photons it can get. Turn your red light spectrum up to 100%. This helps increase yield.
Keep your blue and white light at 100% as well. Be aware that too much blue light will divert energy to the leaves and away from the buds. This will give fluffy buds with a lot of leaves. Very high power in red with a lower level of blue is the key to maximizing yield and dense flowers.
Finishing StageThis is where you manage your potency and chemical profile. Blue and white light produce the best trichomes. Prioritize blue and UVB at 100%, and turn red back down to about 50%. This is how you get those sticky buds everyone is looking for.
Using light cycles to control stages of growth
Plants have evolved to use the sun to gauge what time of year it is and when to start producing fruit. Believe it or not, it's actually the periods of darkness, not light, that will tell the plant when to go from vegetative growth into the flowering stage. You can use this to force a plant into the flowering stage early when you are growing indoors.
Vegetative StageThink of this stage as stems and leaves. This is when the plant is growing fast and trying to get as tall and leafy as possible. The more energy from light your plants receive during this phase, the faster and bigger they will grow. The rule of thumb for vegetative stage is 18 hours of light, 6 hours of darkness . Though some growers will go as far as to give their plants 24 hours of continuous light.
The vegetative stage can last as long as you need or want it to. Usually, you will decide when to transition your plants into the flowering stage based on their size. Some growers go almost directly into flower to keep their plants at a more manageable size. Some growers keep a few plants in veg indefinitely (years) so they can use the plants for cloning. Cloning generally works best if the plants have not reached the flowering stage.
The point is that you, the grower, control how long the veg stage lasts.
Flowering StageThe flowering stage is when the plants start to bud and get ready to produce fruit. In nature, this happens later in the year as the days start to get shorter again. When you move into the flowering stage, you want 12 hours of complete uninterrupted darkness . It sounds odd, but the darkness is the real key to a good flowering stage. Light bleed in a growing environment has confused many a plant and frustrated many a grower when their plants don't bud as expected.
Once your plants go into the flowering stage, the harvest clock starts. As a general rule, the flowering stage lasts about 8 weeks for cannabis. Pure sativas tend to take longer, sometimes up to 12 weeks.
You'll know when to harvest because the trichomes (the little sticky microscopic hairs on the plant) will go from milky white to a copper color as the plant matures. You will likely want a magnifying glass or pocket microscope to really see what is going on. A good high-resolution camera often works well too.
Your plant will be in peak production when the trichomes are milky. When the trichomes are milky it is still an early stage of development, and not quite ready for harvest. Some growers do harvest during this immature milky stage, especially for indica strains as it provides a more energetic feel. As the trichomes continue to mature and turn a copper color, you will get increased potency and increased couch lock.
There is a brief window on many strains where the droplets on top of the trichomes go from milky to crystal clear right before they turn that beautiful copper color. It will look like dew on grass. That's your signal that you are getting really close. Wait until you start to see just a tinge of copper color and then harvest. Once you see 100% copper trichomes, you have missed your window and will only continue to lose potency by waiting to harvest.Do some experimentation and you'll find the perfect harvest time for your tastes.
Types of Grow Lights
High Pressure Sodium (HPS)This is probably the best and most common system in use. HPS is excellent for the flowering/fruiting stages of plant development, and provides an exceptionally intense light that will penetrate the canopy and nourish your entire plant. While its spectrum isn't ideal for the initial veg phase, it can be used on a dimmer as this is a shorter period than the flowering stage. For flowering and fruiting plants, it is the gold standard against which other lights are judged and Russ' preferred grow light.
HPS lights will require a ballast and a hood. Make sure the ballast you use is designed to work with the wattage and lamp type (HPS) you choose. 600 watt is an excellent general purpose size for most applications. Always choose digital lamps if possible. Bulbs should be replaced every 6 months.
Metal Halide (MH)Metal Halide is the traditional bulb of choice for veg productivity. It doesn't have the intensity of light that you get from HPS and does not have the ideal spectrum for the flowering/fruit production. However, if you are growing leafy greens or other vegetables, it is the right choice for you.
MH lights will require a ballast and a hood. Make sure the ballast you use is designed to work with the wattage and lamp type (MH) you choose. 600 watt is an excellent general purpose size for most applications. Bulbs should be replaced every 6 months.
Ceramic Metal Halide (CMH)
CMH lights will require a ballast and a hood. Make sure the ballast you use is designed to work with the wattage and lamp type (CMH) you choose. 315 watt is an excellent general purpose size for most applications. Bulbs should be replaced every 6 months.
Single vs. Double Ended Bulbs Double ended bulbs are basically two HPS/MH/CMH bulbs joined in the middle with connectors on each end. They provide exceptional results if used in the correct environment. However, they are the wrong choice if you use a vented hood, as most home users are forced to do, due to space constraints.
Double ended bulbs are designed to run hot for maximum efficiency. If you use a vented hood, you can't get them up to temperature, they don't run efficiently, and you don't get any significant benefit versus a single ended bulb. When you factor in the increased cost per bulb and the shorter lifespan, single ended bulbs just make more sense for most home growers. If you are in a high-ceilinged environment with exceptional HVAC, the results from double-ended bulbs can't be beat. This is what most Pros traditionally use.
Fluorescent Grow LightsFluorescent grow lights work great up through the veg phase. They are lower intensity bulbs that wont' burn the young plants, and usually give off more blue-spectrum light. They do not have the oomph you really want for the flowering phase, but could be combined with an HPS bulb to up the intensity. You can get decent results running exclusively fluorescent lights, but you will generally get much better yields using a high intensity discharge lamp like HPS, CMH or MH for the later stages of development.
Light Emitting Diode (LED)LEDs have gotten a bad rap over the years, and for good reason. The first batches of LED grow lights just didn't have the power to get light penetration through the canopy to feed the lower parts of the plant. Most budget LED grow lamps still suffer from this problem.
Due to the nature of LEDs, grow lights can be tailored to provide the complete spectrum of light needed by plants by mixing UV, red and blue diodes in a single unit. While you can buy grow lights specifically tailored to red or blue end of the spectrum, they are generally designed to give a good full-spectrum output, giving you a great single light for both the veg and flower stages of plant development.
LED grow lights are generally a little more expensive up front, but an exceptional overall value. There is generally no additional equipment necessary with LED systems as the drivers are built into the units. LED grow lights often are expected to last 4-5 years. This makes them an excellent value, especially when you consider traditional HID systems require a new $100 bulb every six months for optimal results. LED grow lights also tend to use much less power than a traditional HID bulbs, saving you money on electricity. You also will save money on cooling your grow room as LED grow lights produce much less heat (though they do still produce more heat than people think).
The current best of the best in professional grow lights use SAMSUNG LED diodes. Most, if not all, of the lights Russ carries use these LEDs.
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LED Systems vs. Traditional Bulb and Ballast SystemsYou can't go wrong with the tried and true bulb and ballast system. Russ has used HID systems for years and always gets incredible results. If you want guaranteed results, a HID system (specifically HPS) is an excellent choice.
Russ' Tip:Russ' go-to favorite was always the Phantom series of light hoods and digital ballasts with a 1000 watt digital HPS grow lamp. It's a bit of overkill for many home growers, but the results are worth it. As Russ likes to say, "Nothing grows like a 1000 watt HPS."
However, the entire industry is rapidly switching over to LEDs and Russ has been using them almost exclusively for the last few years. Russ really likes HydroFarm's new Phantom PHENO 440 . It gives you Pro performance at a reasonable price point. Everyone who has one LOVES them.
For smaller grow ops and tents, Russ has been extremely impressed with the results his customers get with California Lightworks' SolarXtreme 250 system for under $300.
For a pro setup, PhotonTEK & California Lightworks make incredible grow lights with extremely high light output.
What about a light controller?
This is the closest you can come to producing plants with the taste and overall quality of natural, outdoor grown plants, but with the rapid, protected growth only achieved from a controlled indoor environment.