LEDs are increasingly affordable, easy to use, and often come with innovative features to give your grow an edge. Even so, they’re still accompanied by a learning curve. If it’s your first time experimenting with LED horticulture lights, if you’re making the transition from fluorescent or HID, or you want to get the most bang for your buck, review these common mistakes that can lead to less-than-stellar results.
Putting Your Plants Too Close – Or Too Far Away – From the Lights
The Goldilocks Zone is a term used by scientists to describe the area of space around a star that might provide the right conditions for life. There’s a similar concept in growing: that ideal distance between the plant canopy and the lighting fixtures where plants receive just the right amount of light.
LEDs have a lower operating temperature, meaning you can place the fixtures much closer to the canopy in comparison to HIDs. This is a major plus for uniformity and intensity – but you don’t want to go overboard either, because LEDs can still burn your plants. Growers will want to keep a vigilant eye out for any signs of heat-related stress, such as plants curling away from the light or browning leaf tips.
You may need to adjust the height of your lights as your plants grow. The height you started at may not make sense for your crop as the plants get taller and wider. So, give your facility some flexibility when you’re designing your grow.
Crowding Too Many Plants Under One Light
Similarly, you’ll want to find a balance in how many plants you place under each fixture. In order to determine this, take these aspects into consideration:
- The type of plant you’re growing and at what stage of growth it’s at. If you’re working with small, leafy greens, microgreens or seedlings, you can fit several under one fixture.
- The light fixture’s output. The measurements of photosynthetically active radiation (PAR) and photosynthetic photon flux density (PPFD) illuminate how efficient and uniform your lights are. Most expert growers look for lights that can deliver around 900+ µmol/m2 for PPFD.
- The size of your facility. This might seem like common sense, but you’d be surprised at how many growers buy multiple lights without considering facility design. Ask these questions to guide the design process: how many plants are you expecting to cultivate? How will you access the rows of plants? Are you planning on vertically racking?
Using the Wrong Spectrum, or Forgetting to Adjust It
As plant science has progressed, cultivators have realized that plants respond to tiny adjustments in the light spectrum – whether produced by the sun in a natural setting, or by lights at an indoor grow facility.
Even though these changes may seem hardly noticeable to the human eye, they mean everything to the plant world due to a phenomenon called photomorphogenesis. The light spectrum has an impact on how a plant physically develops, how it smells, tastes or even its chemical composition. When working with the light spectrum, keep these pointers in mind:
- Plants respond best to light wavelengths between 400nm and 700nm, encompassing the blue, green, yellow and red stripes of the light spectrum.
- LEDs are available as spectrally tunable (a little trickier, but worth it if you want full control) and full-spectrum, delivering a preset, scientifically proven combination of light that works well for all plants at any stage. Deciding which LEDs to purchase partially hinges on your preferences as a grower.
- If you’re using spectrally tunable lights, remember to adjust the light based on the plants’ stage of growth: those in the vegetative stage respond well to a little bluer light (this has been shown to lead to strong stalk development and tight internodal placing). Redder light can influence when and how quickly a mature plant flowers.
Giving Your Plants Too Much Light
With the energy efficiency, cool features and efficacy of LED lights, it can be tempting to go hog-wild and run your lights at full blast 24/7. But, as with any biological organisms, plants benefit from a period of rest, too – and no one likes a bright light shining in their face when they’re trying to relax.
A good rule of thumb when it comes to your facility’s light-dark schedule: replicate what nature has already designed. Work with plant biology, rather than against it. This means you’ll need to provide adequate light and dark balance. This is especially important for photoperiodic plants, like cannabis. Cannabis is a short-day plant – they flower when there are increasing nighttime hours.
Settling for Less-than-Best
If you have high standards for the quality of the product you’re producing, you should also have high standards for the equipment you’re using at your grow facility. Lights that are underperforming can result in stunted, unhappy plants – and may even prevent them from reaching maturity.
If you’re overwhelmed by the number of LED choices on the market, ask yourself these questions to help make a smart purchasing decision:
- Do they provide high quality, uniform light? This is a clear priority when comparing lighting options: how effective they are. In this case, you’ll want to ask for PAR and PPFD measurements that accurately reflect the light’s output.
- Are the lights commercial or industrial-grade? Industrial-grade lights are more durable and able to withstand years of constant use. Invest in industrial-grade lights early on – and thank yourself later.
- Are the fixtures waterproofed? Look for the IP66 or IP65 waterproofing certification to protect your lights for the long-term.
Building and investing in a top-performing grow facility certainly takes thought, time, and effort. Catching and correcting these missteps early on in your growing endeavors can prevent you from wasting money and ensure your LED grow lights fulfill their highest potential.
