Growing Tips for LED Grow Lights

led-26354_1280There are a couple of common mistakes that many marijuana growers make when using LED indoor grow lights. These are not having enough light, and not placing the lamp at the correct distance from the plants.

If your plants don’t have enough light, they won’t be able to grow to their full potential. Likewise with light placement: too close to the plants and they will be stunted (and perhaps a little singed if your light runs hot); too far away and the plants will stretch to be closer to the light source, creating thinner, weaker stems.

Each LED grow light will have instructions on how far you should hand the light away from the canopy (ie the top) of the plants. Keep to these guidelines at first, but if you find certain distances work better, you can tweak the distance to get the best results for your grow space.

Light Distance

For example, let’s take the G8 LED grow light. This light comes in different wattages, so naturally the more powerful the light, the further away from the canopy you should place it. Here is a list to help you understand the optimum distances for this light:

  • G8-240: 12-24 inches
  • G8-450: 14-30 inches
  • G8-600: 16-36 inches
  • G8-900: 16-36 inches

You will need to adjust the distance as your plants grow, so the distance between the light and the canopy remains the same. If you want your plants to grow taller, you can move the light a bit further away and they will stretch to meet it.

However, some strains of marijuana naturally grow shorter and bushier. For these plants, keep the light constant so they are not forced to grow too tall. It is also important to keep the light at the same height when your plants begin to flower.

You don’t want to place the light too close to the canopy either. Your plants may become stunted and discoloured.


LED indoor grow lights are a powerful source of energy for your plants. If you do feed your plants nutrient solutions as well, make sure you cut back by about 30% when using a strong LED grow light.


LED grow lights such as Galaxyhydro 300W LED run much cooler than other types of indoor grow light. This means that less water will evaporate in your grow space, which lowers number of times you need to water your plants. If you are soil growing, simply water your plants when the soil is dry – roughly every 2-4 days – to stop them drying out.


As mentioned above, LED grow lights don’t affect the temperature of your grow space too much. This puts you in control of the temperature in your grow room. The best grow room temperature is between 82-85 degrees Fahrenheit. It should remain between 72 and 90 degrees at all times for the best results.

Rest Time

Don’t forget that your plants need their rest too! It is important they get a ‘night time’ when they are not photosynthesising, so switch off the lights on a regular cycle to make sure they get their rest.

Vegetative Stage

In the vegetative stage, your plants don’t need as much light as when they are flowering. Blue light is the most important here, as it is what helps your cannabis to grow. Keep to your light’s height instructions, and don’t forget to adjust as your plants grow bigger.

During this stage, your plants will need light for 16-18 hours each day, with 8-6 hours of darkness. You can keep the lights on 24/7 during the vegetative stage, but it is recommended to give your plants some time to rest by giving them some time in the dark. In this way, you are mimicking the naturally long summer days when the plants would usually grow.

In the vegetative stage you can also begin cloning, pruning, transplanting and bending.

This stage usually lasts around 4-6 weeks, or until the plants are mature enough to begin flowering. In between these stages there is pre-flowering, when small pre-flowers begin to sprout just behind the leaves. Once these begin to appear, you can either wait a week or two more, or switch to flowering straight away.

Flowering Stage

When you are ready to switch to flowering, you will need to do two important things. The first is to make sure the light remains at the same height and is producing lots of red wavelength light (you can even buy an extra red light if you like). The second is to change the day/night cycle so that your plants are getting 12 hours of light and 12 hours of darkness each day. This naturally mimics autumn, which is when these plants usually flower.

After a couple of weeks the cannabis will begin to flower, and this can continue for up to 8 weeks or more. At the beginning the plants will produce flowers rapidly, but this slows as the weeks go by.

During this stage, your plants will also need different nutrients. You’ll want to add more phosphorous and potassium to the mixture, and less nitrogen. This will help the flowers grow big and healthy.

Keep track of how often you feed and water your plants, and how long they have been flowering for. You don’t want to overfeed or overwater them, and you don’t want to harvest too early. Give your plants plenty of time to grow their flowers and you will be rewarded later!


As mentioned earlier, you can clone your plants when they are in the vegetative stage. Once your plants are around 2-3 weeks old you can take a clipping and replant it. Take good care of your cloned plants and follow the guide above to make sure they grow into large, healthy plants.

Hopefully these tips have been helpful for you and have given you some useful advice on growing marijuana indoors. Happy growing!