PAR & DLI Requirements for Strawberries at Different Growth Stages

Strawberries (Fragaria × ananassa) are among the most light-responsive fruit crops grown in greenhouses and indoor farms. Their yield, sweetness, and flowering cycles are all tightly linked to PAR (Photosynthetically Active Radiation) and DLI (Daily Light Integral). Managing these two parameters ensures healthy foliage, strong flowering, and consistent fruiting.

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1. Seedling / Early Growth Stage

Metric	Typical Range	Notes
PAR (µmol·m⁻²·s⁻¹)	150–250	Moderate light supports root and leaf establishment.
DLI (mol·m⁻²·day⁻¹)	8–12	Avoid excessive light before true leaves form.

Tips:

• Use gentle, cool white LEDs with balanced blue and red light.
• Keep temperatures at 18–22 °C (64–72 °F) for steady early development.
• Avoid strong direct light that may dry out tender seedlings.

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2. Vegetative / Leaf Expansion Stage

Metric	Typical Range	Notes
PAR (µmol·m⁻²·s⁻¹)	300–500	Promotes dense foliage and strong crowns.
DLI (mol·m⁻²·day⁻¹)	15–25	Boosts carbohydrate storage for flowering.

Tips:

• Maintain a broad spectrum with enough blue light to avoid elongated stems.
• Ensure good light uniformity—uneven light leads to uneven crown growth.
• For indoor growing, increase DLI gradually to avoid leaf tip burn.

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3. Flowering / Fruit Development Stage

Metric	Typical Range	Notes
PAR (µmol·m⁻²·s⁻¹)	500–800	High light encourages strong flowering and fruit set.
DLI (mol·m⁻²·day⁻¹)	20–35	Sustains fruit sweetness, color, and size.

Tips:

• Strawberries need consistent high light once flowering begins.
• DLI below 20 mol·m⁻²·day⁻¹ may result in smaller fruits and delayed ripening.
• Maintain air circulation to manage heat buildup under intense light.

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Quick Reference Table

Growth Stage	PAR Target	DLI Target	Key Focus
Seedling	150–250 µmol·m⁻²·s⁻¹	8–12 mol·m⁻²·day⁻¹	Root and early leaf growth
Vegetative	300–500 µmol·m⁻²·s⁻¹	15–25 mol·m⁻²·day⁻¹	Crown and foliage expansion
Flowering / Fruiting	500–800 µmol·m⁻²·s⁻¹	20–35 mol·m⁻²·day⁻¹	Sweetness, color, yield

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Why Monitoring PAR & DLI Matters for Strawberries

Light drives both the flower initiation and fruit quality in strawberries. Too little PAR delays flowering, while too much unregulated light can cause leaf scorch and reduced humidity balance.

✅ Consistent DLI leads to:

• Better flower cluster uniformity
• Larger, sweeter berries
• Reduced misshapen fruits

✅ Tracking PAR reveals:

• When sunlight drops below productive levels
• When supplemental lighting is needed to maintain target DLI

Using a Bluetooth PAR & DLI logger like AH-PARDLI makes it easy to:

• Record light trends throughout the day
• Track DLI totals across weeks and seasons
• Export and analyze data directly from your phone — no PC needed