Yes you can have too much light look up DLI, At 16 hours you want like 300 par so with your light in a 4 by 2 I would keep it 2 feet away maybe even 3 feet away depending on how spread out the leds are.
If seedling leaves turn yellow or brown and burn starting with the upper leaves, they may be receiving too much light. You can swap the fixture for one that provides fewer lumens or simply adjust the fixture so it is further away from the seedlings.
But, when it comes to light, it is possible to give your baby plants too much of a good thing. Seedlings need time in the dark, too, and excessive light can do more harm than good.
Seedlings require relatively high light intensity for robust growth. Aim for 25,000-35,000 lux at the top of the seedling canopy. LED and fluorescent grow lights work well for delivering bright, even light distribution. HID lights can also be used but keep them farther away.
Too much LED light can hurt plants, leading to leaf burn and stunted growth. Acclimating plants gradually to the light and monitoring plant growth are key to avoiding these dangers and ensuring healthy indoor plant growth.
Signs of light burn in cannabis plants include upward-pointing leaves and what is known as “bleaching”. Bleaching is the white or yellow discoloration on the leaves closest to the light. Light burn can also be identified when the plant veins stain green as the rest of the leaves turn yellow.
While LED lights do produce some heat, they deal with that heat more effectively than other light types. Plants can grow much closer to LEDs than other lighting types because of this. Usually crops can grow right up to the light without burning.
Is There A Limit To How Long You Can Leave Lights On? Short answer: yes. Even long-day plants need a daily respiration period of at least 6 hours (for seedlings) and ideally 8-10 hours for mature plants. We do not recommend providing more than 14-16 hours of light per day, even for long-day varieties.
Hang your LED grow lights between 20" - 30" above seedlings. As your plants reach vegetative growth, move your LEDs down to about 18". To improve production, try lowering LEDs to 16" during flowering.
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.
While many houseplants can thrive away from any direct light source, seedlings need a good windowsill or some grow lights to provide the energy they need to grow! Moreover, they are sensitive to direct sun, more so than many adult plants are, so picking the right kind of bright spot is crucial.
Keep your seedlings in a warm area and make sure to check them everyday to see if they need water. Water gently when the soil is dry to the touch. Now that your seedlings have reached out from their inner seed casing and poked up and out of the dark soil they will naturally be looking for light.
Check for too much light
Strong, direct sunlight, such as from a south-facing window in summer, can cause brown scorched patches on leaves and give them a washed-out appearance. Shrivelled leaves on shade-loving plants are also a sign that the position is too sunny.
If a plant is overwatered, it will likely develop yellow or brown limp, droopy leaves as opposed to dry, crispy leaves (which are a sign of too little water). Wilting leaves combined with wet soil usually mean that root rot has set in and the roots can no longer absorb water.
Many growers define light burn as the changing of the color of leaves from green to yellow. In most cases, leaves turn yellow, but there can also be another color, such as brown. Keep in mind that yellowish leaves do not always indicate light burn; there can be other issues such as nutrient burn.
Overexposure to grow lights can cause light stress or photoinhibition, where the plant's ability to photosynthesize is inhibited due to excessive light. This can lead to stunted growth, bleaching of leaves, and leaf burn.
Droopy top leaves – Sometimes the leaves are droopy, like they're working too hard and just got tired. Scorched leaves – Leaves that get extreme light levels may turn brown, scorched, and “burnt” or withered, like they went through a crazy heat wave.
Thus with light sources rich in IR, an air temp of 78F is functionally 83F-85F to the plants metabolism. LED's emit no IR, so to achieve similar metabolic rates found in HID or greenhouse conditions at 78F air temp,LED growers need to run the room air temp at 83F-85F.
1) Amount of light
The goal here is to deliver 120-150 micromoles/sec-m2 of PAR to your seedlings. Some people will use a PAR meter to figure out how much PAR they're getting to their seedlings, and will adjust the distance of their lights based on that measurement.
For most indoor plants, including decorative species, a light exposure of 12 to 16 hours during the vegetative stage is recommended. As plants enter the flowering stage, some may benefit from a shorter light duration, typically 8 to 12 hours per day.
You should stop using grow lights under the following circumstances: Light Degradation: If your grow lights have significantly diminished in brightness or effectiveness, it's time to stop using them and consider replacing them to ensure your plants continue to receive adequate light for growth.
Yes, plants can get too much LED light. Like all plants, they need a balance of light to grow and thrive, and too much light can be harmful. High levels of light can cause plants to dry out, wilt, or even burn. Additionally, too much light can inhibit the growth of certain plants.
As a general guideline, LED grow lights should be hung closer to the plants during the vegetative stage (around 18-24 inches) and raised slightly during the flowering stage (around 24-36 inches) to provide the optimal light intensity for each stage.
LEDs' electroluminescence technology is entirely different and does not require heat to produce light; LEDs themselves will not get hot enough to start a fire.