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Why You Need to Adapt Your Cannabis Lighting Over The Full Grow Cycle

Why You Need to Adapt Your Cannabis Lighting Over The Full Grow Cycle

4 min read

If there's one question that never allows a cannabis grower any sleep, it's — are my plants getting enough light? If this question has ever crossed your mind, don't worry, you're not alone. Read along as we describe the lighting requirements of cannabis over the full growth cycle.

If there's one question that never allows a cannabis grower any sleep, it's — are my plants getting enough light?

If this question has ever crossed your mind, don't worry, you're not alone. Considering every professional-grade marijuana grow facility is decked out in ultra-powerful lighting, it's no mystery why many home growers find their lighting solution inadequate.

Luckily for you, your cannabis crop’s success over the full grow cycle isn't dependent on the size of your lights. Instead, the health of your marijuana plants in regards to lighting relies on a parameter known as the daily light integral or DLI for short.

Read along as we describe the DLI requirements of cannabis over the full growth cycle. You'll learn what DLI is, how it affects plants, how it can save you money, and how you can optimally use your grow lights by measuring DLI.

A Brief Recap on DLI

As we've previously described what DLI is, let's take this time to briefly recap the fundamental points regarding DLI.

DLI, also known as the daily light integral, is a term that describes the number of photosynthetically active photons that strike a specific area such as the plant leaves within a 24-hour window. They keyword photosynthetically active photons references to the PAR spectrum, which is used to measure light that is actually usable for plant photosynthesis.

The important part of DLI is that each plant exhibits a maximum DLI in its respective growth stage. Thus, the DLI serves as a measurement that provides cultivators insight into the amount of usable light that a crop needs to flourish. Luckily, effects of DLI on plants is well researched for many plants and we can harness this knowledge to cultivate cannabis better and cheaper.

The Effect of DLI on Plants

The effect of DLI on all plants is monumental.

Without proper DLI, plants would have a tough time surviving. As we can see, plants throughout the world have adapted their DLI according to their environment.

For instance, wheat grows wild in fields across North America, Oceania, South America, and Europe. With an abundance of sun and few competitors, wheat's DLI requirements are on the higher end of the spectrum.

Now, here's a list of effects of supplying the proper DLI on plants:

  • Reduces node spacing
  • Stimulates root and shoot growth
  • Increases stem thickness
  • Increases flower size
  • Increases plant vigor
  • Increases nutrient and water uptake
  • Reduces susceptibility to disease and pest outbreaks

As you can see, the DLI affects the entire plant — not just the leaves.

Therefore, you must provide a proper DLI for your marijuana crop.

The Economical Impact of DLI

Most indoor cannabis growers, or indoor horticulturalists, for that matter, have yet to discover the economic impact of DLI.

Since each plant, such as cannabis, requires a specific DLI one can assume that going over or under the recommended DLI will cause a disproportionate economic impact on your wallet.

Increasing the DLI does not increase plant growth indefinitely – even the opposite

Many marijuana growers pay an unnecessarily high electricity bill because there's a common belief that the more light — the bigger the buds. This, however, couldn't be further from the truth. The more light is not always the better: There is a point where more light does not induce more plant growth or even causes harm to the plant. On the other end, providing too little DLI results in lackluster buds, and a missed growing opportunity.

In other words, there is a sweet spot that you want to hit that encompasses maximum plant growth with minimal DLI so your indoor growing operation won't produce a bigger electricity bill than you bargained for.

Cannabis Plants and DLI

Now, let's talk specifically about cannabis plants and DLI.

Whether you grow marijuana indoors or outdoors, understanding the relationship between light and cannabis plants is essential for a successful grow cycle.

What's The Optimum DLI For Cannabis Plants Over The Full Grow Cycle?

As Cannabis is naturally growing in southern and mountainous areas such as Nepal, Afghanistan, Pakistan, and more it has a sky-high DLI requirement.

In agricultural terms, cannabis plants require full-sun to flourish. Indoors, however, cultivators must consider the light height and light output to achieve the proper DLI.

Cannabis growers can achieve an optimal DLI by understanding the basics of choosing the right grow light and the correct positioning for indoor grow lights.

Here’s a breakdown of the ideal DLI for cannabis plants over the length of the full grow cycle.

The optimal DLI over a full cannabis grow cycle from clone to harvest

As you can see, young cannabis plants do not require the maximum DLI limit. Remember, too much light at such a vulnerable age will result in damage. Alternatively, the DLI must remain high from the vegetative to the flowering stage for optimal results.

How to Optimize The DLI of Your Cannabis Plants With a Grow Light Meter

If you're like us — you want to optimize the DLI for your cannabis plants for the best results in both plant growth and electricity consumption.

However, we can't see the optimal DLI that's striking a cannabis plant's leaf. Instead, you'll need the help of a specialized PAR light meter that provides an accurate DLI reading.

Meet our grow light meter app — a mobile-based PAR light meter that's capable of providing real-time DLI and much more.


If you're ready to fine-tune your grow room to push your crop beyond the limit — download the grow light meter app and make guesswork a thing of the past.

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