By Guest Author Stuart Withers of Green’s Horticulture
If you want robust, healthy, vegetable or flower seedlings, indoor grow lights, known as T5 grow lights, are far superior to growing plants on a windowsill.
A new growing season is an exciting time for any gardener. The time of year has come to plant those seeds and start growing your favorite plants. It’s a great feeling, that’s for sure. However, for anyone who has grown plants before, the importance of growing and nurturing healthy seedlings is always an overshadowing concern.
Healthy seedlings lead to great crops and yields. Naturally, the opposite is true for unhealthy seedlings, which often lead to weak, unhealthy plants. The good news is that with a little knowledge of the light plants need, and the right equipment at your disposal (such as T5 grow lights), you can get your seedlings off to a healthy, flying start each and every time.
What are T5 grow lights?
In case you’re in the dark, T5 grow lights are a type of fluorescent grow light, widely used by both commercial and hobby gardeners. Lighting manufacturers often place several T5 bulbs together in a single unit, which incorporates a reflector to make the most of the available light. T5 grow lights are often favored over other types of grow lights for seedlings because they are less harsh on young plants. They are also preferable to starting seedlings off in a windowsill because they emit a greater amount of the light plants need during this phase of development.
Should you start vegetable seedlings with natural light or T5 grow lights?
Natural sunlight is a mix of all wavelengths, from those that plants can use to those that are of no use at all. Whilst plants have thrived under natural light for millions of years, our scientific understanding of how plants respond to varying wavelengths and color spectrums has resulted in the production of specific synthetic horticultural grow lighting. These synthetic grow lights have been carefully engineered to transmit the specific wavelengths plants respond best to during the different phases of their growth cycle. For example, a blue spectrum grow light will help boost vegetative growth. This is where T5 grow lights come in to play.
Protecting your seedlings from the big wide world by starting them indoors is a logical choice, but it is not without its drawbacks. One key issue is making sure your seedlings grow to be strong enough to survive and thrive in the outside world. It is well known that the quality of seedlings is important to overall growth and yield after they have been transplanted. It is also well known that plant development and physiology depend on how much plant-usable light plants receive, with ‘plant-usable’ being the important term here.
Although placing your sprouted seedlings in a windowsill can help them get enough plant-usable light, there are a few key advantages of using specific grow lights instead. For seedlings, T5 grow lights are often the favored choice.
How much light do seedlings need?
Ensuring seedlings get enough usable light is highly important for healthy growth. After all, you want your seedlings to develop thick stems, thick leaves, and a substantial root system. Healthy development like this depends on the amount of usable light your seedlings have to convert into the energy needed for growth.
Plants can use all light between the wavelengths of 400 – 700 nanometres for photosynthesis, with the exception of green light (which has a wavelength of about 510 nanometres). Plants cannot utilize green light and they reflect it instead; which is why our human eyes see an abundance of green in nature.
How far should T5 grow lights be from seedlings?
“fluorescent lighting should be kept close to growing plants (within 1-2” of plant tops) and the area they can effectively cover is limited to the surface area of the bulb. For example, when growing seedling in a standard 10 x 20” seedling tray you’ll want four tubes or two shops light fixtures (~5” wide) to cover the 10” tray width, otherwise your plants on the edges will stretch towards the middle.”
Kansas State Research and Extension
The benefits of blue and red light for plant growth
The specific wavelength range that plants use is commonly referred to as Photosynthetically Active Radiation (PAR). All light emitted in the PAR wavelength range is absorbed by specific cells in plants called photopigments. These cells absorb this usable light and use it for photosynthesis and sugar production. The two most common photopigments in plants are Chlorophyll A and Chlorophyll B, both of which absorb light with the highest efficiency in the blue (in particular 439nm and 469nm) and red (in particular 642nm and 667nm) wavelengths.
Because of the abundance of Chlorophyll A and Chlorophyll B, plants are best at utilizing light in the blue and red spectrums, each of which has different effects on plant growth. The blue spectrum of light encourages healthy vegetative growth whereas the red spectrum triggers the hormones responsible for inducing flowering and fruiting.
Therefore, for seedlings and during the early stages of growth, the best results can be had using T5 grow lights that emit light primarily in the blue spectral range. Blue light will boost the development of leaves, which in turn will give a greater opportunity for the plant to capture the energy from light, further boosting growth and developing healthy roots. Seedlings grown under a T5 grow light will often perform better than those placed in a windowsill because you are giving them the specific light they need to carry out photosynthesis.
T5 grow lights also offer other benefits
A common nightmare with seedlings is ‘leggy-ness’ which leads to weak, elongated stems. Leggy-ness is often the result of too much heat and not enough light, a circumstance that can happen all too easily with plants placed in a windowsill or other indoor location. One of the reasons T5 grow lights are becoming increasingly popular is because they emit only a little heat and can therefore be placed just a few centimeters above your seedlings. This close proximity eliminates leggy plants. Seedlings that are bathed with blue light from a short distance will have shorter internodal lengths, resulting in stronger plants that can focus their energy on healthy vegetative growth and root development.
Grow lights give even light dispersion to seedlings
Just like giving one plant the right nutrition and depriving another will result in a difference in growth, giving one plant an abundance of light and not another will do the same. One thing that T5 grow lights are brilliant at is providing an even spread of light.
For example, T5 bulbs in a 4-foot long by 2-foot wide 8-bulb array will cover that whole area with an even spread of light, because the multiple T5 bulbs will all emit the same light over the same area.
Grow lights are space savers
T5 grow lights are also great space savers. For gardeners propagating multiple plants at once, finding enough windowsills in the home can be problematic.
T5 grow light units often come in a compact design, most measuring only a few centimeters in depth. A standard cupboard could easily house several of these T5 units stacked on top of each other, making the most of vertical space and turning a cupboard into a seedling growing powerhouse.
Are T5 grow lights a necessity for starting vegetables?
T5 grow lights are by no means a necessity for your seedlings. After all, Mother Nature and natural sunlight have been growing great plants for millions of years. However, T5 grow lights do incorporate into their design our scientific understanding of what makes plants flourish. They are particularly useful if you have ongoing issues with leggy seedlings or are worried that your plants may not be getting enough usable light.
About the guest author: Stuart Withers works for horticultural and Hydroponics retailer Green’s Horticulture and is a self-confessed geek when it comes to growing plants indoors. With science as a weapon, he uses the power of PAR and grow lights to cultivate great, healthy plants. He particularly likes T5 Grow Lights as they always manage to get his young plants off to a flying start.
I have only used LED grow light, the full spectrum can satisfy the growth of indoor plants.
I find T5’s are great for raising seedlings but I wouldn’t recommend them for flowering fruits or vegetables.
My experience with t5 is that they burn very hot and I was having trouble finding the right distance to keep them from the plants which created the path I followed to this blog. What I found on my tomato seedlings was ashen colored spots that eventually worked their way through the leaf. It could be water spots does not look like fungus of any sort. I am running them almost a foot off the leaves and they are doing much better. The old shop lights I started with could actually touch w/o trouble.
I’ve been using T5’s for years and have had no problems. But yes, with some varieties, you may produce the equivalent of sun scald when the lights sit only an inch above plants. I keep mine at about 10″ and have no problems.
Great explanation on the matter of wave lengths. But I wonder why you focused exclusively on T5 size tubes. Is this what you’re addressing when you talk about saving space, or were you comparing lights to windowsills? T8 and T12 grow lights come in a variety of sizes and could fit the bill as well.
Steve: Thanks for your comment. We’ll be covering other grow lights in more detail in follow-up articles. Yes, this one focused on the benefit of T5’s over sunlight from a window.