For optimal results, for vegetative growth choose fluorescent light bulbs that are labeled either as "Cool White" or "Cool" colored (also labeled as "6500k" colored).
In general, I recommend changing to stronger grow lights like LEDs or HIDs for the flowering stage because they will usually give you double or more yields/watt of electricity. Unless you keep your plants very small, they will need more light to produce buds than a fluorescent light can usually produce. If you're in a dire situation where your plants have grown too big and you can't afford to get a different type of light, you can supplement your fluorescent tubes with additional light, for example you could supplement their light with a few CFL(compact fluorescent light) bulbs wherever you notice any "shadowy" areas. This is only a minor fix – the real fix is to grow very short plants or upgrade to a bigger light for the flowering stage.
There are many different levels of fluorescent grow lights including the T5, the T8 and the T12. I strongly suggest sticking with the T5 style of fluorescent grow lights for cannabis because they give off the most amount of light for the size, and are specifically designed to be able to support taller plants up to 24 inches.
The biggest problem with fluorescent tubing is that the light that they give off is only useful for about a foot or so. That's why they're kept so close to your plants.
Any part of the plant that is further away then 1-2 feet from the fluorescent grow lights is not getting an optimum amount of light, especially in the flowering stage when plants need a lot of light to produce buds.
However, you can use either type of lights during either stage and still get good results. People also use "Daylight" (5000K) bulbs with success.
With the new high output lights such as the T5, fluorescent lights can be used until the plants are about 24 inches tall, which is just enough to grow a very short plant through to the flowering stage when you control your marijuana plant's growth through the vegetative stage.
The great thing about fluorescent grow lights is that they don't get very hot, and they can usually be kept 1-4 inches from the tops of the plants at all times without having to worry about burning your cannabis leaves or buds.
For flowering, choose bulbs that are "Warm White" or "Soft White" colored (usually labeled as "2500K" or "3000K").
T5 Fluorescent lights over motherplants.
Yes, you can use a T5 fluorescent light to flower a pot plant. The benefits of using this type of lighting is the lack of heat that they generate. Because they’re not super-warm, you can place your plant tops within just a few inches of the light. The disadvantage of flowering under fluorescent lighting is the lack of light intensity and penetration. This makes the Screen of Green (ScrOG) method ideal as you can train the flowering tops to create a level canopy close enough to the light.
Just wondering if you would use a T5 to flower a pot plant? – Raymond M.
HIDs (high-intensity discharge) are even more powerful, but they aren’t as energy-efficient and they use a lot of power. As such, they can give off quite a bit of heat. You may need to invest in a ventilation system to counteract this, leading to a higher cost.
Establishing the space where you will grow your plants is crucial. Many strains can thrive outdoors, but most cultivators opt for indoor set-ups where they can control the temperature and light thoroughly. Since marijuana strains can be picky and sometimes require different conditions at different growth stages, indoor growing can provide you with the highest yield – if you do it right.
5 Best Fluorescent Lamps for Growers in 2022
This warm fluorescent bulb is designed for flowering plants, potentially negating the problem that often occurs with CFLs during the flowering stage. Most growers use this bulb with a reflector to ensure the best distribution of light.
As you can see, choosing the best fluorescent light is a bit of a trade-off. That’s why professional growers will change between different types of lights during different stages of growth. If you’re not that serious, though, and are just planning on growing one or two plants, then fluorescent bulbs will work just fine.
Why Use Fluorescent Grow Lights for Cannabis?
Growers recommend using this light in spaces that measure 3’x3’ or more. The reflector itself is 19” x 19” x 5”.