How Does DLI Relate to “Full Sun,” “Partial Shade,” and Other Light Terms?

Gardeners and growers often use terms like “Full Sun”, “Partial Sun”, “Partial Shade”, and “Shade” to describe how much light a plant needs. But these categories are subjective and vague—what does “full sun” mean in measurable terms?

That’s where DLI (Daily Light Integral) comes in: it turns those soft terms into solid numbers.

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What Is DLI Again?

DLI stands for Daily Light Integral, measured in mol/m²/day. It represents the total number of photosynthetically active photons a plant receives in one day. Unlike lux or lumens, it focuses on what plants actually use for photosynthesis.

It gives you objective data, regardless of whether your light comes from the sun, grow lights, or both.

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Matching DLI with Traditional Sunlight Labels

Here’s how common horticultural light categories roughly translate to DLI values:

Light Category	Approx. DLI Range (mol/m²/day)	Description
Full Sun	20–40+	Open field, no obstructions. Ideal for vegetables, fruits, cannabis, cacti.
Partial Sun	15–20	Receives sun for 4–6 hours/day, or filtered light. Good for many flowers and herbs.
Partial Shade	10–15	Less than 4 hours of direct sun, dappled light. Ferns, impatiens thrive here.
Shade	0–10	North-facing windows, deep forest, indoors far from light. Suitable for low-light species.

This table helps you translate tradition into data—and use tools like PAR/DLI meters to measure if your environment meets the requirement.

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Why It Matters

• “Full sun” in winter isn’t the same as in summer
  The sun’s angle and intensity change throughout the year. You may assume your plant is getting enough—but is it really hitting 20+ mol/m²/day in December?
• Trees or windows block more light than you think
  Your “partial sun” patio may only provide 7 mol/m²/day instead of 15—leading to poor flowering or leggy growth.
• Grow lights need to be measured, not guessed
  “100W grow light” means nothing if the DLI under it is only 5. Use a meter to verify actual performance.

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Use a DLI Logger for Real Insight

With tools like the AquaHorti AH-PARDLI, you can:

• Automatically record DLI under natural or artificial light
• Compare readings across seasons and growing areas
• Optimize lighting for every plant type

You’ll stop guessing and start growing with precision.