LED Grow Lights Explained

Do LED Lights Work?

They absolutely do! Various universities and government agencies like NASA have used LED Grow lights to grow a variety of flowering, fruit bearing plants and leafy greens. Many other indoor growers and hobbyists have documented their indoor grow with LED grow lights on the internet! Follow our indoor growing tips to help produce optimal growth and yield. Below you will find more detailed information about the vegetative growth stage of a plant's growth cycle.

For optimal growth and yield you must use your LED grow light properly and follow best growing practices. The biggest mistakes people make with LEDs are overwatering, using too much nutrients, not having enough light and not placing the light at the proper distance. If you do not provide your working area with enough light coverage, you can expect less than robust growth. Similarly, incorrect light placement will not have optimal results. Placing a light too close will stunt growth, too far will cause stretching. Follow the recommended coverage areas listed on the Details Page of each light for optimal light penetration and coverage. Keep in mind that there are many variables to indoor growing, so you may want to add or remove some light depending on your own specifics.

Plants in Vegetative Growth

Vegetative growth is maintained with 16 or more hours of light. You can even keep the plants under 24 hours of light and they will continue to grow in this stage. However, the recommended growth cycle is 18 hours of light during the vegetative growth stage. This light cycle will create an environment that mimics the photoperiod in the summer with long days. During the vegetative stage is when you will start to reap the benefits of your LED grow lights. During this period you will save on your electricity bills and get superior growing results. In the vegetative stage, plants need less intense lighting than in the flowering stage. It is during the vegetative growth stage that cloning, transplanting, pruning, and bending are all initiated.

Turn your LED grow light ON for 18 hours a day and then turn the light OFF and leave your plant in the dark for another 6 hours. Your plant will need four to six weeks of this cycle to be ready to start the flowering stage. Pre-flowers are the first indication that the plant is ready to move into the next stage of growth. The pre-flowers grow at branch internodes just behind the leaf spur in around the fourth week of vegetative growth, when the plant is six to eight weeks old. When you start seeing pre-flowers forming this means that the plants are ready to go into the flowering stage. You can continue to grow in the vegetative growth stage or switch to flowering at this point. The pre-flower looks like a regular female flower with white fuzzy pistils. The pre-flowering can take from one to two weeks. Wait to induce flowering until pre-flowers have appeared. Induce flowering by switching your light cycle to 12 hours of uninterrupted darkness and 12 hours of light.

Flowering with LED Grow Lights

In nature flowering occurs in the fall, after the long hot days of summer. The long nights and short days of autumn signal the start of flowering. With LED grow lights we mimic the seasons by changing the light cycle from 18 hours a day to 12 hours. Give your plants 12 hours of uninterrupted darkness and 12 hours of light to induce visible signs of flowering in two weeks or less. Adding more light to the plants also help give bigger flowers and yield. Once you have induced flowering for one to two weeks and flowering starts, it can last can last eight weeks or longer.

During flowering, growth patterns and chemistry changes in the plants. Stems elongate, leaves grow progressively fewer blades and flower formation is rapid at first then slows. Phosphorus and potassium uptake increase to promote floral formation. Your nutrients should have less nitrogen and more potassium and phosphorus during flowering. Don’t give nutrients too often as this can cause your plant to get nutrient burned. You should use about 30% less nutrients with LED flowering grow lights as compared to MH/HPS systems. Do not overwater and do not harvest too early.

Flowers initially appear near the top of the terminal growth and gradually develop on lower branches starting at the tips and moving downward. Flowers have white pistils which look like hairs. The pistils are attached at the base to an ovule which is contained in a light green pod called a calyx. Pistil packed calyxes form dense clusters along the stems. These clusters are called a top or cola. The calyxes form develop rapidly for the first four weeks after which they grow at a slower rate. Must of the harvest weight is then put on the last two or three weeks of growth when the calyx formation has slowed which is why it is so important to not harvest too early because the majority of your yield comes the last couple weeks. The pistils will continue to swell and change in color from white to amber to reddish brown. Once this occurs you are ready to harvest your plants.

Proper Distance to Hang Full Spectrum LED Grow Lights

Keeping the proper distance between your full spectrum LED grow lights and your plants is important to robust photosynthesis and growth. Your LED grow light provides the wavelengths of light your plants need for growth and flowering. Plants will reach for the much coveted light source just like they grow towards the sun in outdoor conditions. The general rule of thumb is to increase the distance between the top of the plants’ canopy and the light source as the light becomes more intense. This means that hydroponic LED grow lights of different power ratings will perform best at different distances.

Specific hanging distance recommendations can be found on each product page. Maintain these distances as your plants grow in the vegetative stage. For plant stretching increase the distance from the the plants to the light. For shorter, bushier plants decrease the distance. As you raise the light, the plants will reach for the source and grow taller. If you keep the light fixed, the plants will grow tall to a certain point, then grow wider and more dense. Putting lights too close to the plants may be too intense and stunt growth and create discoloration. It is best to follow the recommended distances and adjust as necessary. During flowering the lights can be left at a constant distance.

Since LED grow lights emit 90% less heat than traditional HID lighting such as high pressure sodium or metal halide bulbs, your plants will not dry out or burn if you happen to place your LED grow light to close to your plants. However, your plants’ growth will be stunted if the light is hanging too low. Within a week you will notice that your plants are not experiencing robust growth and the leaves may become discolored. If you do experience this result, adjust by increasing the distance between your light and the plants. Follow the recommended hanging distances and your plants will thrive in your grow room.


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