Horticulture top lighting

Typical PPFD and DLI values per crop

Plants absorb radiation mostly in the 400-700 nm visible range and convert CO2 uptake and water into oxygen and glucose.

The amount of absorption in each wavelength depends on the cellular structure of the plant and may differ from species to species somewhat.

Another important parameter is Daily Light Integral which is defined as the total number of photons impinging per square meter in one day.
DLI is measured in units of mol/m2.d and each plant has a specific requirement of DLI for its growth.

Values ranging between 6-18 mol/m2/d are common depending on the particular plant.

There is a relationship between PPFD and DLI which is given by:
DLI=PPFD x light hours per day x (3600/1000,000).
You can see from this formula that there is a trade-off between PPFD and number of light hours required to achieve a certain DLI value.
If there is a certain amount of natural lighting available for a green-house, it has to be subtracted from the original DLI value for proper artificial lighting fixture calculations.

Taking into account the DLI, PPFD and number of light hours per day, you can calculate the total number of fixtures required in a green-house to illuminate the crops.

Calculation from DLI to PPFD

12 moles / 16 hr photoperiod / 60 minutes / 60 seconds = 0.000208 moles
(This gives us the amount of moles delivered per second per square meter)
0.000208 moles x 1,000,000 = 208 µmols per second per meter squared (µmol/sm²)
As a rule of thumb below values can be taken when your crops are not specified

Greenhouse

  • Vegetative Growth (Leafy Greens/Herbs): Minimum 17 mol/m2/d
  • Flowering Crops (Peppers/Tomatoes): 20-40 mol/m2/d

Indoors

  • Microgreens: 6-12 mol/m2/
  • Vegetative Growth (Leafy Greens/Herbs): 12-17 mol/m2/d
  • Flowering Crops: 15-40 mol/m2/d


Minimum ○Good ◎High ●Average Daily Light Intergral (Moles/Day)
Spices24681012141618202224262830
Ferns (Pteris Adiantum)









Maranta









Phalaenopsis (Orchid)









Saintpaulia









Spathiphyllum









Forced Hyacinth
Forced Narcissus
Forced Tulip
Aglaonema








Bromeliads








Caladium
Dracaena








Nephrolepsis








Streptocarpus








Hosta
Hedera (English Ivy)
Begonia







Sinningia







Schlumbergera
Cyclamen






Exacum






Heuchera






Coleus (Shade)




Impatiens, New Guinea




Iris, Dutch (Cut Flowers)




Kalanchoe




Lobelia
Primula




Impatiens



Pelargonium Peltatum (Ivy Geranium)


Begonia (Fibrous)
Senecia (Dusty Miller)
Fuchsia

Euphorbia (Poinsettia)

Lilium (Asiatic and Oriental)

Lilium Longiflorum (Easter Lily)

Antirrhinum

Chrysanthemum (Potted)

Dianthus

Gazania

Gerbera

Hibiscus Rosa-Siniensis

Lobularia

Pelargonium Hororum (Zonal Gera-Nium)

Rose (Miniature Potted)

Salvia Splendens

Schefflera

Angelonia


Aster


Salvia Farinacea


Iberis


Catharanthus (Vinca)


Celosia


Chrysanthemum (Garden)


Dahlia


Echinacea


Ficus Bejaminia


Gaura


Hemerocallis


Lantana


Lavendula (Lavender)


Tagetes (Marigold)


Petunia


Phlox (Creeping)


Rudbeckia


Sedum


Thymus


Verbena


Viola (Pansy)


Zinnia



Alstroemeria (Cut Flower)



Capsicum (Pepper)



Chrysanthemum (Cut Flower)



Dianthus (Carnation)



Gladiolus (Cut Flower)



Lycopersicon (Tomato)



Rose (Cut Flower)





What are typical μmol/s.m² values for horticulture lighting?

What light level for what type of crop?
PlantMin (μmol/s.m²)Max (μmol/s.m²)Typical (μmol/s.m²)
Tomato170200185
Pepper70130100
Cucumber100200150
Cannabis Vegetative growth280400350
Cannabis Flowering6501,000850


What light level for what potted plant?
PlantMin (μmol/s.m²)Max (μmol/s.m²)Typical (μmol/s.m²)
Orchid / Phalaenopsis80130105
Dendrobium130260195
Bromelia406050
Anthurium608070
Kalanchoë6010582.5
Potted chrysanthemum406050
Potted rose406050
Geranium406050


What light level for what cut flower?
PlantMin (μmol/s.m²)Max (μmol/s.m²)Typical (μmol/s.m²)
Chrysanthemum105130117.5
Rose170200182
Lily8010090
Lisianthus170200185
Alstroemeria6010582.5
Anthurium / Orchid - cut8010592.5
Freesia7010587.5
Gerbera8010592.5
Tulip254032.5
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