T5 grow lights are one of the best types of lights you can use to grow any kind of plant, from vegetables to the most delicate flowers. This is because T5s are extremely efficient, allowing you to save money on electricity while still providing bright, powerful light. They also have features you can customize to build the perfect set-up for any size and type of indoor garden.

Many indoor growers are already familiar with the virtues of T5s, but even if you know your T5 fixtures and more or less know how they work, you might need help with some things, because specifics like color temperature, hanging height and light cycles might not be as easy to figure out.

First things first, for those of you who do not know the basics, a T5 grow light is a tube-shaped fluorescent light that is 5/8-inch in diameter. In terms of the light’s name, the “T” is for tube shape, and the “5” is for the 5 in the 5/8-in. unit of measurement.

These lights are mainly used as additional or full-on artificial lighting for plants to re-create the natural light spectrum. They can be used in many different environments and conditions, from greenhouses to indoor gardens. Here are some tips on how to use them to your full advantage.

Choosing the Right T5 Grow Lights

To use T5 grow lights properly, there are a couple of things you need to know that will determine how successful you will be at growing under these lights. The first thing is how to choose the right T5 fixture and the right bulbs.

  • Fixtures: When it comes to choosing a grow light fixture, there are a couple of things to think about. First is the size requirements for this grow light. There are more than a dozen size variations, so you need to figure out the size of your indoor garden and then fit the lights to your space. T5 grow lights typically come in two different lengths and around six different bulb configurations. The most common T5 grow lights are 2- or 4-ft. long and have 1, 2, 4, 6, 8 or 12 bulbs per fixture. If you are thinking of growing only a few small plants, you might get away with having a 1- or 2-bulb set-up that is 2- or 4-ft. long, but if you want to grow a whole bunch of plants, you will have to invest in an 8- or 12-bulb set-up that is 4-ft. long. This larger size will cover a lot of plant mass without using too much electricity.
  • Bulbs: When it comes to choosing bulbs, there are even more options to choose from. Bulbs not only come in different energy varieties, but also in different color temperatures. When choosing between normal output (NO), high output (HO) and very high output (VHO) bulbs, I recommend going for the middle ones. HO bulbs are the best of both worlds—they are efficient, yet long-lasting, and will provide super-bright light for your plants.

As far as color temperatures go, different plants have different light requirements, so I can only suggest a general guideline, which is to start with 6,500 Kelvins bulbs when plants are in the vegetative stages of growth. This is approximately the color temperature of light on a summer day. Otherwise, use 3,000 K bulbs when plants start to flower. This color temperature is warmer (more sunset-like), with a red tint to it, so it will best suit blooming plants.

Setting Up the T5 Lighting System

Now that you have selected the right fixture and bulbs, it is time to set up your grow lights. The first thing you need to think about when setting up T5 grow lights is the height, or how high above plant canopies you are mounting your fixtures. Although T5 lights are famous for emitting very little heat, this doesn’t mean you can put the bulbs an inch above plant canopies, as this distance will still damage the plants.

The best height for a T5 grow light is about 6-8 in. above the plants, but you should increase that gap to 12 in. if your plants don’t like heat or they are in the seedling growth stage. If the T5 fixtures are at this height, the light from the bulbs will be intense enough and bright enough for plants, but the heat won’t be able to damage your plants. Some plants need less-intense light, so just monitor your plants and see what works for your indoor garden set-up.

Light Cycles

You are almost ready to go—all that’s left is figuring out the right light cycles, and then you can turn on your lights and start growing. A light cycle refers to how many hours you keep the lights turned on for and for how many hours you leave your plants in the dark. Light cycles are used to simulate night and day. Outdoor plants get a certain amount of hours of light and dark to grow properly, and you need to simulate these conditions indoors, too.

Light cycles tend to differ based on what plants are being grown under artificial lighting. For example, there are 12/12-hour cycles, 18/6-hour cycles and even 24/0-hour cycles of light/dark periods. To find the right cycle for your plants, I suggest either researching the needs of the variety of plant you’re growing, or basing your cycle on what the approximate light cycle would be if the plants would be growing outdoors during their season. Typically, more light means faster growth, which results in bigger plants and bigger yields no matter what you are growing.

Other Lighting Parameters

You are finally all set to turn on the lights and start growing, but there are a few words of caution before you begin, though. Since you are growing plants indoors and your growroom might be small, you need to watch not only how much water your plants need, but the temperature of the room the plants are in as well.

Plants tend to drink more water in different stages of growth, but just like humans, they need more water the hotter your growroom gets. This is why you need to install a ventilation system if your grow lights make the room too hot, and why you need to closely monitor how much water the plants need by checking their soil humidity level every couple of days.

By following the steps outlined above and monitoring your plants regularly, you should be able to grow great plants and get big yields using T5 grow lights.