Understanding PAR and DLI Needs for African Violets

African violets (Saintpaulia spp.) are among the most popular indoor flowering plants in the United States — admired for their soft leaves and colorful blooms.
Their success depends heavily on one key factor: light intensity and duration.
Let’s explore how PAR (Photosynthetically Active Radiation) and DLI (Daily Light Integral) affect their growth through each stage.

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1. Seedling / Propagation Stage (Weeks 1–4)

Metric	Range	Notes
PAR (µmol·m⁻²·s⁻¹)	50–100	Very gentle, diffused light encourages root formation.
DLI (mol·m⁻²·day⁻¹)	4–6	Prevents leaf curling and dehydration during rooting.

Tips:

• Use filtered LED or indirect sunlight; avoid direct midday exposure.
• Maintain temperatures around 22–25 °C (72–77 °F) and moderate humidity (~60%).

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2. Vegetative Stage (Weeks 4–10)

Metric	Range	Notes
PAR (µmol·m⁻²·s⁻¹)	100–200	Encourages compact, symmetrical rosette formation.
DLI (mol·m⁻²·day⁻¹)	8–10	Supports healthy leaf expansion and chlorophyll buildup.

Tips:

• Keep the LED lights 20–30 cm (8–12 in) above the canopy.
• Too much light causes leaf edges to bronze; too little leads to long petioles and pale leaves.

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3. Flowering Stage (After ~10 weeks)

Metric	Range	Notes
PAR (µmol·m⁻²·s⁻¹)	150–250	Sufficient for consistent, colorful blooming.
DLI (mol·m⁻²·day⁻¹)	10–12	Boosts flower count without stressing leaves.

Tips:

• Maintain 12–14 hours of light per day; longer exposure doesn’t necessarily mean better flowering.
• Stable lighting schedule helps extend bloom duration.

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Summary Table

Growth Stage	PAR (µmol·m⁻²·s⁻¹)	DLI (mol·m⁻²·day⁻¹)	Ideal Condition
Seedling	50–100	4–6	Gentle, diffuse light
Vegetative	100–200	8–10	Balanced brightness
Flowering	150–250	10–12	Strong but indirect light

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Why Monitoring PAR and DLI Matters

African violets are sensitive to both too much and too little light.
Measuring PAR and DLI helps you maintain the perfect balance — preventing leaf burn, improving bloom frequency, and achieving consistent color intensity.

With the AquaHorti AH-PARDLI Bluetooth PAR/DLI Logger, you can:
Track light intensity and daily accumulation automatically
View light curves directly from your phone — no Wi-Fi or account needed
Adjust LED distance or shading based on real data