Light intensity can cause severe damage to your seedlings to the point where they die or are stunted.
High Light Stress In Plants
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.
The amount of light each seedling needs will vary from plant to plant. Those that require less light at an adult stage don't need as much as those that enjoy full sun throughout their life cycle. Seedlings exposed to too much light or heat will wither and die.
Plants can't gorge on artificial sunlight forever.
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.
Unfortunately, grow lights can hurt and burn your plants. However, it isn't the amount of light that's the problem, but rather the heat that the lights emit. What is this? Indoor plants kept too close to light bulbs can experience bleaching of their leaves and even burns if the heat is too intense.
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. Otherwise, do the math and scale up to a brighter light.
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.
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.
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.
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.
1. 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. 2.
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.
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.
During the seedling phase, when plants are tender, lights are suspended higher. Generally, LED lights should be about 24-26 inches during this phase, and then lowered to 18 to 22 inches during the vegetative and flowering stages of growth.
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.
To fix leggy seedlings and to encourage your seedling to grow stronger and branch out, you can pinch back the 2nd, 3rd or 4th set of true leaves that appear on a plant. Never pinch or cut anything back leaving a stem without leaves on the top of it (see photo), rather pinch back just above the lower set of leaves.
' plants do require a daily respiration period of at least 6 hours per day (for seedlings) and ideally 8-10 hours for more mature plants. Therefore we do not recommend providing more than 14-16 hours per day of light, even if you are growing long-day-loving varieties and trying to induce flowering/fruit from them.
Light Intensity
Over time, this can deplete the plant's water reserves and leave insufficient water for vital processes such as photosynthesis. If the plant's capacity to dissipate heat is depleted, or if the amount of heat generated exceeds the plant's ability to dissipate it, the plant will suffer heat damage.
It is also important because lights placed too close to the canopy can cause burning, bleaching, stunted growth, or discoloration.
After the plants reach the final stage of grow, and get to their full size, we do not need to use the grow light that much. Even though they've already stopped growing, you shouldn't ditch the grow light completely. A fully-grown plant would still need about 12 to 14 hours of light per day.
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.
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).