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 your plant's leaves start to turn yellow or brown or are starting to curl up, your light may be too close to your plant and may be burning your plant! (Although there are other reasons that curling and browning might happen, those are for other articles!)
This 100W LED light was just too close to the seedlings, causing them to get burned and turn purple and suffer, they can get burned just like we do in the bright sun! It is true that your seedlings need bright light to grow healthy and strong—but, too bright a LED light could actually damage them if it's too close!
Seedlings under grow lights do well when getting 14-18 hours of light exposure a day. But remember that more light isn't better. Some people mistakenly think they are doing seedlings a favor by keeping the lights on 24/7, but all plants need a period of rest.
Can you burn plants with LED grow lights? Even though LED lights are the safest for your plants, they can still hurt them and even burn their leaves if they're too close. LED lights can even cause photo-bleaching in plants that don't need plenty of light throughout the day.
For seedlings, keep the lights at least 8 inches away from the top leaves. If the plant starts to dry out, move the light a bit farther away. For vegetative and flowering stages, the distance the lights should be from the plant depends on the wattage of the bulb.
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.
While some plants need less darkness time than others, too much light will impede any growth schedule over time. Too much light can also refer to the intensity of the light. Intense, direct light is great for some plants, but it will damage (or even kill others).
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).
The LED lights are very concentrated and can damage your eyes. This is truer than ever with today's high power LEDs. Never look directly into LEDs and wear sunglasses. The bottom line is that LED grow lights are no more dangerous than any other type of grow light.
If a plant is getting too much light and suffering from high light stress, its leaves may look as though they have burned or simply are falling off. In many cases, the soil will be dry to the touch, too.
Keep grow lights suspended low over the seedlings. Even with a very bright grow light, seedlings may get leggy if it's hung too high. Most fluorescent lights can stay as close as a few inches above seedlings, while LEDs usually need to be kept higher to avoid burning the plants.
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.
Therefore, the easiest fix for leggy seedlings is to give them more light ASAP! Even if you place them in a south-facing window, the average amount of sunlight in late winter to early spring (when seed starting usually takes place) is much less than the 12 to 16 hours needed for strong seedling development.
The General Rule
The distance will actually depend on the type of LED grow lights you've decided to purchase. For example, LED lights of 1000 watts are recommended to be placed 36 inches away from the plants.
Generally yes, you can use any LED Light to grow plants, especially white LEDs as they have a good mix of different wavelengths plants need. However, regular LEDs typically don't have sufficient light output or power to help plants flower.
How long to keep grow lights on plants depends on a number of factors. As a general rule of thumb, most vegetables and flowering plants need 12 to 16 hours of light per day, with flowering plants at the top end of that range. Plan on giving most plants at least 8 hours of darkness per day.
The first and the most important symptom of light burn is yellow leaves. The green leaves of the plant turn yellow. This happens to the leaves at the top of the plant and starts from the tip of the leaves. If you have noticed this symptom, it is time to take action.
The answer to this one is simple. Your grow lights should be turned on (or your seedlings should be put under lights) as soon as the first seed starts to sprout. Many types of seedlings grow very fast, and they will begin reaching for the light as soon as they emerge. So give them plenty of it right from the start.
The sad thing about light burn is there are no treatments or methods to fully recover your plant back to its healthy and green state. But fear not, you can still make great use of your plants.
Causes of Leggy Seedlings
The stems grow thin because the plant is desperately reaching its leaves towards the light. Seeds that are started late winter or early spring, when the sun is still low in the sky, are prone to this type of growth pattern.
Not enough light
“Legginess” in seedlings is caused by low light, as plants stretch to reach a light source. Eventually, this will result in weak stems, and the plant will struggle to support itself. If you have a sunnier window, consider moving your plants there. Otherwise, you may need to include artificial lights.
Possible Causes
Too little nutrients can stunt growth, too much nutrition can damage the roots and prevent the seedling from taking in water. Low temperatures. Most seeds like a soil temperature of around 65°-75°. Excessive moisture and overwatering.
Moving the grow light closer will increase the light intensity which can maximize photosynthesis. However, if the grow lights are too close above plants, they can cause wider, more sprawling growth or can even damage the plant. Plants require different levels of light depending on each stage of growth.