With all of the grow lighting options out there, it can certainly be overwhelming to decide which type of setup is right for you. All of the letters and numbers found on various types of grow lighting bulbs and fixtures can be confusing, especially for new growers. Fortunately, an easy and readily available option for seed starting and growing clones or transplants is the T5 fluorescent grow light. These inexpensive and highly versatile lights are great not only for beginners and hobbyists, but for those looking to increase the size of their growing operations.
Armed with a little knowledge about horticultural grow lights, propagation methods, and what the best grow lights for each situation are, it is easy to land on T5s as the user-friendly choice for growers. They are versatile and easy to assimilate into most growing setups and situations. Let’s take a look at some of the features of T5s and how best to use them to see if they are a good choice for your growing areas.
Features and Benefits of T5 Lighting
T5 lighting is a form of fluorescent lighting which is manufactured in the shape of a tube (hence the “T”). The “5” in T5 is a reference to the size of the bulb. In this case, the T5 has a 5/8 inch diameter bulb (T8s are 8/8ths of an inch, or simply one inch while T12s are 12/8ths of an inch, or 1.5 inches in diameter). When the T5 is plugged in, it produces ultraviolet (UV) light by heating up the mercury, argon, and phosphorous gases inside each bulb. Each T5 tube is coated on the inside with materials known as “phosphors”. The combination of phosphors and how they interact with the UV lighting gives a range of different temperatures and wavelengths of light. Because of their unique properties, T5s are very efficient in their creation of light and use of energy.
The T5 burns relatively cool as compared to most other bulbs, making them a safer and more cost-effective grow light than many of the types currently on the market. T5s are found to be available in two different wattages. You can find 24W bulbs (2 feet long), 39W bulbs (3 feet long) and 54w bulbs (4 feet long). Compared to other, more traditional types of grow lighting that can be up to 400W per bulb, and often require cooling equipment to remove the heat that they emit, T5s are clearly more energy-efficient.
Color temperatures will vary with different types of T5 options. Cooler temperatures, such as 6400 K, will give off light containing blue wavelengths. These are needed primarily during the vegetative phases of growth. Warmer colors, such as 2700K, give off wavelengths of light which are found on the red end of the light spectrum which plants utilize during the budding and flowering phases of growth.
Those are not the only choices though. There are T5s that offer individual wavelengths to target and promote specific characteristics. These characteristics include, but aren’t limited to branch strength, resin development, and terpene production. When used in quantities, as they are recommended, the aggregated output of light (lumens) from these groupings of T5 lights is equivalent to more powerful High Intensity Discharge (HID) lighting.
A wide range of plants can be grown using T5s. Almost any commercially available plant can be grown using T5 bulbs. In addition to medical and high value crops, houseplants, vegetables, fruiting and ornamental plants, both annual and perennial, can all be grown under T5 lighting. The number of bulbs and the wattage will need to be adjusted according to the crops grown and their specific needs, but there is a combination out there to successfully grow almost any plant. Fewer tubes are sufficient for seed starting and growing small herbs or microgreens. Larger plants may need as many as eight T5 tubes to provide sufficient light output in order to photosynthesize and properly utilize nutrients. Larger operations may use numerous racks of multiple T5 tubes in series.
Another benefit of the T5 light bulb or fixture, is that it can be kept fairly close to the plants’ canopy, making them an ideal choice for smaller growing areas. An average distance between the top of the canopy and the light tube is about 12 to 18 inches (30 to 45 cm). This can vary some with the intensity of each individual T5 tube and what it is designed for, but it is a good starting point. If your plants start getting too “leggy”, bring the light source closer to the canopy. This can be as close as 5 inches (12.5 cm) away. This is far enough away to not burn tender plants or give them too much UV light, but close enough to give them the full range of intensity of the T5 bulbs from a safe distance. Increase the distance from the light source if plant leaves start to curl or show any sign of bleaching.
This close range of the T5 to the plants themselves, is not only a benefit, but a necessity in order to take full advantage of the light output of the T5. If crops are more than 2 feet (60 cm) away from the light source, much of the illumination given off from the light tubes is wasted and does not even reach the plants. Too close to the plant canopy (less than 5 inches), and the T5s can harm the foliage of the plants.
So, T5s can offer benefits that more traditional lighting options and even newer LED lighting cannot. They can provide the quality and quantity of light needed, all without overheating the growing area or disfiguring the plants’ leaves by burning or bleaching them. Let’s look at some more specifics of how to use T5 lighting fixtures with different stages of plants.
T5s for Seed Starting and Seedlings
T5 grow lighting has become a new standard for starting seeds and young plants to the point where some growers would say that they are the best available grow light on the market for getting their plants off on the right foot. They have found their niche in these early stages of plant development because they provide a full spectrum of light and do not burn too hot for tender young plants. They are also favored because of their relatively low price point compared to LEDs, or HPS bulbs, or even some other types of fluorescent lighting.
T12 lighting used to be a standard bulb for seed staring. These were however, phased out in 2012, and growers often made the switch to the T8. This, however, did not prove to be the best option for most growers. T5s quickly filled that newly formed niche because of the above mentioned benefits, but also because of their efficiency. Their ratio of energy consumption to light output makes them an attractive option for growers.
Seedlings need both a close source of full-spectrum light and one that does not burn too hot. The T5 lighting is intense enough to penetrate the canopies of young crops which encourages side growth and not just vertical growth like some other types of grow lighting. Because of their lower operating temperature, T5s are less likely to damage or stunt developing plants due to their intensity. The T5s are highly capable of operating for the full 14 to 18 hours per day required for plant development without building up too much heat. They are also easily adaptable to systems with timers.
The T5 light fixture can be found in a range of color temperatures. Varieties that offer color temperatures around 6400 Kelvins will most closely mimic natural sunlight. Seedlings are sensitive and easily stressed by extremes in the environment. T5 bulbs are an excellent and highly efficient choice to get plants off on the right path to healthy growth and abundant yields in the absence of natural sunlight for crops. Some growers do not even bother to switch over to other types of lighting from the T5s once the plants grow beyond their early stages and use them for their total propagation.
For Growing Transplants, Clones and Mature Plants
T5 light fixtures can serve as the main light source for your entire grow from seeding to harvesting, regardless of time of year. This is because, in recent years, the industry has been churning out more high-output fluorescent bulbs unlike the weaker and less efficient ones of the past. The T5 light is one such example of these and are a great choice for growing in areas where the light source has to be in close proximity to the plants. Because they are cooler burning, they can be very near to the top of the plants, sometimes within even an inch depending on the stage of growth.
During the vegetative stage of growth, using T5s marked as “Cool” or “Cool burning” are optimal. At this stage, the T5s can be nearly on top of the plants, literally. Then, during the flowering stage, the lighting option selected should be switched over to T5s marked as “warm white” or “soft white”. The lights should be raised one to two feet above the canopy at this stage. For plants that will be transplanted into the field or grown outside in the spring, the T5 is a great option for keeping plants growing over the wintertime, without letting them get too large. T5s can be left on all night during the growth stage, without fear of the plants starting the flowering phase too soon.
The T5 fixtures are prized by some growers for their ease of use, and their size. They do not take up a lot of space in the grow room. They are efficient, in that they are able to give off light evenly, ensuring that even plants further away can receive sufficient amounts of light. Another benefit to their efficiency, is that they do not put the same strain on the electric bill as other types of grow lights. In general, the longer the tube, the more efficient they are at producing light and using less energy.
The T5 light fixture is not perfect for all situations though. T5 lighting is often not the best choice for large-scale grows. They work best in tight quarters and in locations where plants either can’t or should not grow beyond a certain point either due to space restrictions, varietal characteristics, or the preference of the grower. For plants larger than 24 inches tall, another lighting source should be considered. If you prefer to use another grow light type as your primary lighting source, T5 fixtures can still lend a hand as a supporting grow light.
T5s as Supplemental Lighting to Existing Fixtures
Fluorescent T5 grow lights can be used for both supplemental lighting as well as a specific type of additional lighting: side lighting. As the name implies, supplemental lighting is used in addition to some other type of primary lighting. It is generally done to increase the color, spectrum, or amount of light on a given crop. T5s could be used to supplement LEDs, HPSs, MHs, or even other fluorescent setups. Side lighting refers to supplemental lighting used to give the sides and even undersides of the crops’ canopy illumination that more closely resembles the amount and location of light that the plants would receive if grown outside. This practice increases in bigger yields on the buds of lower branches.
Fluorescent bulbs like the T5 are an easy choice for supplemental lighting in the grow room or greenhouse. They are usually low profile and easily mounted almost anywhere, so that light can be directed anywhere onto the crop that additional lighting is wanted. They can be used in tandem with the primary grow lights, or just used when naturally lighting conditions aren’t providing the amount of light needed for healthy crops. When they are used to give additional lighting to the lower portions of the crops and the sides that typically do not receive enough lighting, they are unsurprisingly referred to as side lighting.
Side lighting is not always necessary but can be helpful in recreating the kind of light that plants would receive naturally at sunrise and sunset. This side lighting can help to promote a crop’s natural growth pattern, promoting wider, lower branches. This increases the likelihood of lower buds getting pollinated. Side lighting is also used effectively in growing areas that are small or cramped. In these situations, it is not uncommon for only the tops of the crops to get the benefit of grow lighting, leaving the lower branches unable to properly photosynthesize. T5s are a safe and easy addition to give some side lighting in these environments. Side lighting can also be used in very large grow areas.
Large-scale grows in massive greenhouses or grow rooms can have shadows cast on parts of the crops from features of the structure of the greenhouse or grow area. Due to the setup or bench placement/ other large pieces of equipment the space may have some areas that are darker than desired. Side lighting in these situations helps the crops to get the right amount of light so that they can properly metabolize the nutrients and other feed that they are being given and help to prevent some nutrient-related disorders. Ultimately, each grower needs to determine if side lighting is a cost-effective solution for them.
Side lighting of course adds to the cost of producing a crop. Growers need to decide if the increased buds or yields sufficiently offsets the investment in equipment. With T5s as side lighting (as opposed to other types of grow lighting), the return on investment (ROI) can be assumed to be much quicker than with most other types of supplemental grow lighting. Growers may, however, opt to try other yield-increasing methods before deciding on investing in side lighting.
