PAR & DLI Requirements for Microgreens at Different Growth Stages

Microgreens—tiny but nutrient-packed young plants—have become a favorite in hydroponic, vertical, and indoor farms.
Because their growth cycle is short (typically 7–21 days), getting the PAR (Photosynthetically Active Radiation) and DLI (Daily Light Integral) right is essential for achieving rich color, compact structure, and intense flavor.

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1. Germination Stage

Metric	Typical Range	Notes
PAR (µmol·m⁻²·s⁻¹)	50–120	Very gentle light encourages root initiation without drying the surface.
DLI (mol·m⁻²·day⁻¹)	3–6	Allows slow metabolism and uniform sprouting.

Tips:

• Use low light or even darkness for the first 24–48 hours depending on species (e.g., basil vs. broccoli).
• Keep humidity above 80% and temperature between 20–24 °C.
• Avoid direct intense light that can dry seed hulls prematurely.

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2. Cotyledon Expansion / Early Growth Stage

Metric	Typical Range	Notes
PAR (µmol·m⁻²·s⁻¹)	150–250	Boosts chlorophyll production and leaf expansion.
DLI (mol·m⁻²·day⁻¹)	8–12	Supports quick canopy fill and bright coloration.

Tips:

• Maintain consistent distance between LEDs and trays (usually 20–30 cm).
• Increase air circulation to strengthen stems.
• Slightly increase blue light to improve color tone and nutrient content.

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3. Pre-Harvest / Finishing Stage

Metric	Typical Range	Notes
PAR (µmol·m⁻²·s⁻¹)	250–350	Encourages thicker leaves, deeper pigmentation, and higher antioxidant levels.
DLI (mol·m⁻²·day⁻¹)	12–18	Ensures dense, flavorful harvests with strong coloration.

Tips:

• Avoid DLI above 20 mol·m⁻²·day⁻¹, which may cause tip burn or premature yellowing.
• Spectrum rich in red (around 660 nm) enhances anthocyanin formation in red or purple varieties.
• Reduce light slightly in the last 12–24 hours before harvest to maintain moisture balance.

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Quick Reference Table

Growth Stage	PAR Target	DLI Target	Duration	Key Goal
Germination	50–120 µmol·m⁻²·s⁻¹	3–6 mol·m⁻²·day⁻¹	1–2 days	Root initiation
Cotyledon	150–250 µmol·m⁻²·s⁻¹	8–12 mol·m⁻²·day⁻¹	3–7 days	Leaf development
Pre-Harvest	250–350 µmol·m⁻²·s⁻¹	12–18 mol·m⁻²·day⁻¹	3–10 days	Pigment & flavor buildup

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Why Measuring Light Matters in Microgreen Production

Because microgreens grow fast, minor variations in PAR or DLI can change everything:

• Too little light → pale, stretched seedlings.
• Too much → scorched leaves or reduced taste quality.
• Inconsistent DLI → uneven growth between trays or shelves.

With the AquaHorti AH-PARDLI Bluetooth PAR/DLI Logger, you can:
Track daily PAR fluctuations automatically.
Check light trends directly on your phone (no Wi-Fi needed).
Export 180-day CSV data to optimize shelf height, light spacing, and photoperiod.