What Kind Of Fluorescent Lights To Grow Plants?

fluorescent grow light bulb

A Compact Fluorescent Light (CFL) bulb

The short answer is: any type of fluorescent light will help plants grow.

But it’s not quite so simple.

While you can use any type of tube or bulb and see results, you want to provide the kind of light your plants want most. That’s how you get the best results.

So what type of light do your plants need?

That depends on a few things.

  1. Are they plants that flower or ones that don’t?
  2. If they flower, they need different type of light depending on their current stage of growth.
  3. Are they already getting some natural light or will they be growing under artificial light only?

 

CFL or T5 Tubes? And Which Ones?

Agrobrite fluorescent grow fixture

An Agrobrite  T5 fluorescent fixture

Before we get into the specifics on the types of bulbs or tubes, let’s first decide whether we want to go with fluorescent tube lighting or with compact fluorescent bulbs.

The answer is simple. If you’ve got a very small garden, CFL bulbs (pictured at the beginning of the article) make the most sense. If your garden is large enough to warrant a larger T5 tube fixture, go with that and perhaps supplement the light from above with a few CFLs .

As for which bulbs to get, it doesn’t matter with CFL bulbs. You can just get any standard bulb from your local Home Depot or Walmart or order online. There is no need to get a specialized (and overpriced) grow bulb. They’re basically the same thing. It’s just a way to get more of your money.

For T5 fixtures, I recommend the Agrobrite line from Hydrofarm (pictured above). We reviewed them here, but the quick summary is that they cost about the same as most no-name fixtures from China, but work far, far better.

You can use regular fluorescent bulbs from any local store, but for larger fixtures like this, it make more sense to buy from a company specializing in horticultural lighting. And Hydrofarm is the biggest name there is.

Now, let’s take the first question from above and tackle plants that flower and those that don’t separately. The second and third questions will be answered naturally as we go along.

 

What Fluorescent Bulbs for Growing Flowering Plants (Marijuana, tomatoes, etc)?

Flowering plants need more and different light than non-flowering plants. But only during the latter stages of growth.

In the beginning, flowering plants need the same light as non-flowering plants. When they are seedlings and when they are growing (vegging), they need light that contains more blue than at other times. This is also often referred to as ‘cold light’. It is the kind of light our sun gives off naturally during daylight hours.

When the plants have grown enough to begin fruiting or flowering, they need more light than before and they prefer a warmer light, i.e. light that contains more red.

So how can we give them the light they need with fluorescent bulbs?

By using bulbs with varying color temperatures. During the seeding and vegging stages, we want to use bulbs labeled ‘cool white’ or ‘daylight’. They will have a color temperature (usually indicated on the package) in the range of 6000K to 6500K. During flowering, ‘warm white’ bulbs are ideal, with a color temperature of 2700K to 3500K.

It might seem like a hassle to change bulbs when it is time to go from vegging to flowering, but it’s really only a big deal if you have a very large garden with a lot of lights. And if that is the case, you should not be using fluorescent lighting anyway, as the disadvantages outweigh the advantages once a grow gets too large.

However, if you just don’t want to bother with having to change the bulbs, you can get lights with a color temperature in the middle, somewhere around 5000K. These bulbs will work fine for all stages of growth. In reality, any bulb will work for any stage, but using bulbs that provide the right kind of light yields much better results.

In most cases, you will want to supplement the light you use during vegging with some additional bulbs. Personally, I just hang a few CFL bulbs (warm light) here and there to add some more output and really stimulate flower and bud production.

 

What Kind of Fluorescent Bulbs for Plants that Don’t Flower?

If you are growing plants that don’t flower, like cacti, herbs, lettuce, etc. then you do not need to worry about providing warmer light during flowering. You just need to get some ‘cool white’ or ‘daylight’ bulbs and use them all the time. No need to switch lights.

August 8, 2017

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