Tips for Growing Under LED Grow Lights

The latest LED grow lights eviscerate HPS lighting in terms of performance, with fixtures like the Omega Infinity 3.0 Pro reaching a ground-breaking 3.0 micromoles of useable light per watt. The yields that customers are hitting with these lights blow everything else out of the water, which is why LEDs make up the the vast majority of the new fixtures that we sell.

It's worth noting that, to maximise productivity with LEDs, you may need to make some slight changes to your approach, as there are a few pitfalls to avoid. Don't worry, though, because these changes are all relatively minor, and we've created a list of areas to focus on to make life as easy as possible and to ensure that you get the very best results.

1) Lower grow room temperatures

The current crop of LED grow lights produces up to 50% more plant-usable light per watt of electricity than the very best HPS grow lights!

The higher the efficiency a grow light has, the less energy is lost as heat. Older, high-intensity discharge grow lights (like high pressure sodium and metal halide) put out a lot of additional heat, which can be a help or hindrance, depending on the outside temperatures.

When growing with next-gen LEDs, grow room conditions will be much cooler on average, so be sure to keep an eye on the temperature of the grow-space. If readings drop below 24 degrees centigrade during the lights-on period, then you should think about reducing the airflow rate of your extraction system with a fan speed controller.

In colder months you may well need to use a grow room heater to compensate for the reduced heat levels, which will ensure that conditions stay in the right ballpark. Tube heaters are great for taking the chill off, but if you need something a bit more heavy-duty, we've got heaters that will easily meet your demands. A thermostat is a worthy addition, as it will switch your heating equipment on and off as needed, maintaining perfect temperatures.

2) Slightly less frequent watering

Because there is less heat and infrared light emitted by an LED grow light, there will be less evaporation from the soil and less transpiration through the plant's leaves. This means that you will probably need to water your plants slightly less frequently.

Soil should be allowed to dry a little before being watered again in order to avoid waterlogging and to reduce the risks of root rot infections. It is important to not allow the soil to dry out completely, though. Many growers use something called the 'heft test' to decide the right time to water. Get to know the weight of a pot full of watered soil, and also a pot full of soil that is getting a bit dry by literally lifting (hefting) it up. By using the 'heft test' you'll soon get to be able to judge when it is time to water again.

4) Lower nutrient strength is needed

The general consensus among growers seems to be that nutrient strengths can be as much as 25-30% lower when growing under LED than HPS. Use a quality EC/CF/PPM meter such as the Bluelab Truncheon to help you give your plants the correct nutrient strength.

Learn to read your plants and look for the signs of overfeeding or underfeeding. As you gain experience, you will learn when to increase or decrease nutrient concentrations.

4) You may be able to lower light height

Generally speaking, LED grow lights can be hung closer to the plant canopy than HID lighting. Always follow the manufacturers' recommendations on how high to hang your grow light and watch out for light bleaching and/or heat burn. Many LED grow lights have passive heatsinks which make them a bit heavy for easy roll light hangers; instead, we suggest Rope Ratchet Hangers.

The glorious full-spectrum light output of modern-day LEDs can be put to good use right the way through the cycle, from seedling and cutting to harvest. Young plants need much lower levels of light intensity than mature plants, so make sure you start with the light raised up and the output settings at the lowest level. You can then lower the light height and increase the output setting as your plants develop. If any sign of damage appears or if your plants look stressed, raise the height of the light (or reduce the output setting) immediately. Stressed plants often have leaves that hang downwards looking wilted and sad. An unstressed plant looks 'perky' with its leaves pointing up, searching out light.

6) Keep an eye on humidity levels

The lower excess heat generated by LEDs can cause humidity readings to increase. The water holding capacity of the air is relative to the temperature, hence the name 'relative humidity'. The higher the temperature, the greater the air's capacity to hold water. By lowering temperatures, you also lower the air's water holding capacity, thus increasing the relative humidity reading (all else being equal). This issue is compounded by the fact that your extraction system is often running at lower airflow levels, reducing the capacity to remove excess moisture. Higher levels of relative humidity can lead to issues with rot and powdery mildew. Keep a close eye on your hygrometer. Follow the previous steps carefully (reducing feeding rates and increasing low temperatures) and your readings will drop into line.

7) Boost CO2 levels

One way to take advantage of the extra light output generated by modern LEDs is to supplement with CO2. Mother Nature CO2 Generator is a hassle-free way of boosting CO2 way beyond ambient levels.

  • Simple, quick to set up and cost-effective
  • Five litre bucket covers 1.2m square
  • Ten litre covers 1.2m x 2.4m
  • Comes with air pump to move CO2 around
  • Automatically activates at 22 degrees
  • Lasts for around six months

If you want to keep your eye out for the latest and greatest LEDs, be sure to check out our Facebook/Instagram pages - @onestopgrowshop

Check our full range of LED grow lights out here.

Happy Growing!

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