For best overall results, BIOS recommends that you grow your seedlings under an 18/6 light cycle using Icarus LED lamps, set 24-36 inches from the leaf canopy, and under a blue light spectrum for their first 10-14 days. 18/6 simply means 18 hours of light and 6 hours of darkness.
Seedling Daily Light Needs
Leave the grow lights on for 14 to 16 hours per day to provide light for the young seedlings. It's best to turn the light on early in the morning and turn it off around dusk.
How Many Hours Of Lighting Do Seedlings Need? Seedlings need 14-16 hours of light every single day, without fail. Don't leave them on for 24 hours a day though. Like us, they need to rest at night.
The more lumens, the brighter and more powerful the light is. Vegetable seedlings and other “full sun” plants require about 2000 to 3000 lumens (at minimum) per square foot of growing space. So, if you're growing just a single standard tray of seedlings, using a grow light that emits 3000 lumens is sufficient.
A: In general, you should not leave grow lights on 24/7. Plants need a light-dark cycle to develop properly. It's believed that they truly do “rest” during periods of darkness, and probably use this time to move nutrients into their extremities while taking a break from growing.
Light intensity can cause severe damage to your seedlings to the point where they die or are stunted.
For many years, fluorescent shop lights were the go-to seed starting bulbs for gardeners, but LEDs have quickly replaced them as the standard choice. LEDs are usually more expensive than fluorescent bulbs, but they are very energy-efficient and long-lasting.
Red light stimulates vegetative growth and flowering (but if a plant gets too much, it will become tall and spindly). Blue light regulates plant growth, which makes it ideal for growing foliage plants and short, stocky seedlings (but too much will result in stunted plants).
If you want to keep your plants healthy and happy, then they must have the right amount of light. Dimming lights is a great way to provide just enough lighting for plants while still saving a little on energy costs.
Hang your LED grow lights at 18" - 24" at 25 percent intensity for seedlings. Bring your LEDs to about 18" during vegetation and set the dimmer to 50 percent. Keep your LEDs at 18" and turn them to full intensity.
All seedlings require sunlight. Seedlings will become leggy and fragile and will not produce to their potential if they do not have sufficient light. Table 1. Soil temperature conditions for vegetable crop germination.
Give your new seedlings light.
Seedlings should be watered once a day or every other day, depending on how much sun and heat they get. Remember that seedling roots are fairly close to the surface and they're growing in a small amount of media, so they don't need a deep soak the way larger plants do.
In contrast, blue light is considered equally effective as green or red light at driving photosynthesis. Thus, while blue light can appear somewhat dim to us, it has high energy and is useful for plant growth applications.
Once those seeds sprout, proper seedling care is essential, and that includes supplying the growing plants with the right amount and quality of light. It is true that seedlings need lots of bright light to grow healthy and strong—but they also need a period of darkness in order to thrive.
The Myth That White Light is Good
The problem with this logic is that plants don't need light that looks white to us, nor do they need light that mimics the sun. Plants do best with a light that has a lot of red and blue and smaller amounts of green and yellow.
A sprouted seed is no longer a seed but a seedling, a miniature plant. The most important thing to consider and deliver is adequate plant light. Seedlings need more light than full grown plants, ideally as much as 16-18 hours a day. Additional light may be required for seeds started during the winter months.
Red/Blue LEDs
This combination is more energy efficient than “white” or full spectrum LEDs because blue and red LEDs have the highest photon efficacy compared to other colors i.e. they convert the highest amount of electricity in photons, so you are getting more growth from your plants per dollar spent.
Most flower and vegetable seeds germinate best when the temperature of the germination medium (potting mix) is 70 to 75 degrees Fahrenheit.
Telltale Signs of Too Much Light
The most apparent sign is leaf burning. This typically causes the yellowing of leaves at the top of the plant but the veins stay green, and the leaves take on a yellow or brown, burnt look.
If the LED grow light is lower than 200W, the height for LED grow light above plants should not exceed 12 inches. For the wattage between 200W to 400W, keep the LED grow light about 12 inches to 20 inches from plants. The height about 20 inches to 28 inches is suitable for LED grow light in 400W to 600W.
Location is Everything – grow lights should sit no more than 3″ above the leaves of seedlings. Anything further away will cause legginess as the plants reach for the light source. Make it Windy – plants also need a little stress to develop strong stems. Blow on your seedlings every day, or install an oscillating fan.
As an unofficial rule of thumb, many growers work on the basis that: You need 20-40 watts of power per square foot. Lower wattage LEDs of around 200 watts should sit between 12-20 inches from the top of the plant. Higher wattage LEDs of 1000 watts and above should sit between 36-46 inches from the top of the plant.
When growing with T5s, start at 12 inches above your plants and work from there. If you see plants start to curl up, raise your lights until they start opening back up. If your plants start to stretch out and become weaker, lower your lights, but make sure not to lower them to five inches above your plants.
630-660 nm (Red) Light: This light is essential for germination and stem growth, as well as leaf expansion. It is also used to regulate periods of growth and flowering. Too much red light, or red light used alone, will produce tall plants that appear stretched with thin leaves.