DLI ↔ PPFD ↔ photoperiod

Cited targets

From the genetics.guru grow library, in the units each source used. Grades: strong and moderate are peer-reviewed; community practice is untested.

• DLIpropagation (cuttings)5–15 mol/m²/dModerate

  Derived: 54 umol continuous ~5 mol; 200 umol x 16 h = 11.5 mol; 250 umol x 16 h = 14.4 mol.

  3 sources

  1. Campbell SM, Anderson SL, Brym ZT, Pearson BJ (2021-07-29). Evaluation of substrate composition and exogenous hormone application on vegetative propagule rooting success of essential oil hemp (Cannabis sativa L.) — PLOS ONE 16(7):e0249160
  2. Moher M, Llewellyn D, Golem S, Foley E, Dinka S, Jones M, et al. (2023-02). Light Spectra Have Minimal Effects on Rooting and Vegetative Growth Responses of Clonal Cannabis Cuttings — HortScience 58(2):215-221
  3. Holweg MMSF, Sae-Tang W, Wang Y, Kohlen W, Heuvelink E, Marcelis LFM (2025-11). Mother Plant Age and Light Intensity Minimally Alter Adventitious Root Formation in Medicinal Cannabis — HortScience 60(11):2034-2046
• DLIvegetative26–52 mol/m²/dModerate

  Biomass, leaf area, branching rose linearly 17.9-51.8 mol/m2/d.

  2 sources

  1. Collado CE, Hwang SJ, Hernández R (2024-06-07). Supplemental greenhouse lighting increased the water use efficiency, crop growth, and cutting production in Cannabis sativa — Frontiers in Plant Science 15:1371702
  2. Rodriguez-Morrison V, Llewellyn D, Zheng Y (2021-05-11). Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment — Frontiers in Plant Science 12:646020
• DLIflowering (12 h)26–78 mol/m²/dStrong

  Derived: 600-1800 umol x 12 h x 0.0036.

  3 sources

  1. Rodriguez-Morrison V, Llewellyn D, Zheng Y (2021-05-11). Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment — Frontiers in Plant Science 12:646020
  2. Llewellyn D, Golem S, Foley E, Dinka S, Jones AMP, Zheng Y (2022-09-27). Indoor grown cannabis yield increased proportionally with light intensity, but ultraviolet radiation did not affect yield or cannabinoid content — Frontiers in Plant Science 13:974018
  3. Holweg MM, Curren T, Cravino A, Kaiser E, Kappers IF, Heuvelink E, et al. (2025-02). High air temperature reduces plant specialized metabolite yield in medical cannabis, and has genotype-specific effects on inflorescence dry matter production — Environmental and Experimental Botany 230:106085
• PPFDautoflower, after first ~2 weeks400–900 µmol/m²/sModerate

  Transferred from photoperiod veg/flower studies; at 18-20 h, 900 umol gives DLI 58-65 mol.

  2 sources

  1. Rodriguez-Morrison V, Llewellyn D, Zheng Y (2021-05-11). Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment — Frontiers in Plant Science 12:646020
  2. Collado CE, Hwang SJ, Hernández R (2024-06-07). Supplemental greenhouse lighting increased the water use efficiency, crop growth, and cutting production in Cannabis sativa — Frontiers in Plant Science 15:1371702
• PPFDpropagation (cuttings)100–250 µmol/m²/sModerate

  Rooting fraction unaffected across 50-250; higher light increased root and cutting dry mass. Cuttings also rooted at ~54 umol (DLI ~5).

  3 sources

  1. Holweg MMSF, Sae-Tang W, Wang Y, Kohlen W, Heuvelink E, Marcelis LFM (2025-11). Mother Plant Age and Light Intensity Minimally Alter Adventitious Root Formation in Medicinal Cannabis — HortScience 60(11):2034-2046
  2. Moher M, Llewellyn D, Golem S, Foley E, Dinka S, Jones M, et al. (2023-02). Light Spectra Have Minimal Effects on Rooting and Vegetative Growth Responses of Clonal Cannabis Cuttings — HortScience 58(2):215-221
  3. Campbell SM, Anderson SL, Brym ZT, Pearson BJ (2021-07-29). Evaluation of substrate composition and exogenous hormone application on vegetative propagule rooting success of essential oil hemp (Cannabis sativa L.) — PLOS ONE 16(7):e0249160
• PPFDvegetative400–900 µmol/m²/sModerate

  Greenhouse veg growth not saturated at DLI 52 mol (~800 umol x 18 h). Upper value limited by climate/irrigation capacity rather than biology.

  2 sources

  1. Collado CE, Hwang SJ, Hernández R (2024-06-07). Supplemental greenhouse lighting increased the water use efficiency, crop growth, and cutting production in Cannabis sativa — Frontiers in Plant Science 15:1371702
  2. Rodriguez-Morrison V, Llewellyn D, Zheng Y (2021-05-11). Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment — Frontiers in Plant Science 12:646020
• PPFDflowering600–1,800 µmol/m²/sStrong

  Yield linear to 1800 (ambient CO2 ~437 ppm). Economic optimum is site-specific (electricity, cooling, CO2). Cannabinoid concentration mostly unaffected above ~600.

  6 sources

  1. Rodriguez-Morrison V, Llewellyn D, Zheng Y (2021-05-11). Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment — Frontiers in Plant Science 12:646020
  2. Eaves J, Eaves S, Morphy C, Murray C (2020-03). The relationship between light intensity, cannabis yields, and profitability — Agronomy Journal 112(2):1466-1470
  3. Llewellyn D, Golem S, Foley E, Dinka S, Jones AMP, Zheng Y (2022-09-27). Indoor grown cannabis yield increased proportionally with light intensity, but ultraviolet radiation did not affect yield or cannabinoid content — Frontiers in Plant Science 13:974018
  4. Holweg MM, Curren T, Cravino A, Kaiser E, Kappers IF, Heuvelink E, et al. (2025-02). High air temperature reduces plant specialized metabolite yield in medical cannabis, and has genotype-specific effects on inflorescence dry matter production — Environmental and Experimental Botany 230:106085
  5. Sae-Tang W, Heuvelink E, Nicole CC, Kaiser E, Sneeuw K, Holweg MM, et al. (2024-12). High light intensity improves yield of specialized metabolites in medicinal cannabis (Cannabis sativa L.), resulting from both higher inflorescence mass and concentrations of metabolites — Journal of Applied Research on Medicinal and Aromatic Plants 43:100583
  6. Westmoreland FM, Kusuma P, Bugbee B (2021-03-23). Cannabis lighting: Decreasing blue photon fraction increases yield but efficacy is more important for cost effective production of cannabinoids — PLOS ONE 16(3):e0248988
• PPFDpropagation100–250 µmol/m²/sModerate

  Fraction rooted unchanged 50-250; higher light = more root mass. Spectrum not critical.

  3 sources

  1. Holweg MMSF, Sae-Tang W, Wang Y, Kohlen W, Heuvelink E, Marcelis LFM (2025-11). Mother Plant Age and Light Intensity Minimally Alter Adventitious Root Formation in Medicinal Cannabis — HortScience 60(11):2034-2046
  2. Moher M, Llewellyn D, Golem S, Foley E, Dinka S, Jones M, et al. (2023-02). Light Spectra Have Minimal Effects on Rooting and Vegetative Growth Responses of Clonal Cannabis Cuttings — HortScience 58(2):215-221
  3. Campbell SM, Anderson SL, Brym ZT, Pearson BJ (2021-07-29). Evaluation of substrate composition and exogenous hormone application on vegetative propagule rooting success of essential oil hemp (Cannabis sativa L.) — PLOS ONE 16(7):e0249160
• photoperiod (light hours)autoflower, whole cycle18–20 hCommunity practice

  No autoflower photoperiod yield trial exists. DLI logic favours longer days; 24/0 showed photo-oxidative stress markers in hemp (16/8 best physiologically).

  3 sources

  1. Growers Network Forum thread '18/6 vs 24 hour light on' (2022-01-16). Autoflower growers compare 24/0, 20/4 and 18/6
  2. Šrajer Gajdošik M, Vicić A, Gvozdić V, Galić V, Begović L, Mlinarić S (2022-08-26). Effect of Prolonged Photoperiod on Light-Dependent Photosynthetic Reactions in Cannabis — International Journal of Molecular Sciences 23(17):9702
  3. Rodriguez-Morrison V, Llewellyn D, Zheng Y (2021-05-11). Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment — Frontiers in Plant Science 12:646020
• photoperiod (light hours)vegetative (photoperiod cultivars)18–20 hModerate

  15 h allowed incomplete inflorescences in Suver Haze; 18 h did not. 24/0 caused thylakoid membrane damage indicators in hemp.

  3 sources

  1. Park J, Collado CE, Lam VP, Hernández R (2023-04-23). Flowering Response of Cannabis sativa L. ‘Suver Haze’ under Varying Daylength-Extension Light Intensities and Durations — Horticulturae 9(5):526
  2. Šrajer Gajdošik M, Vicić A, Gvozdić V, Galić V, Begović L, Mlinarić S (2022-08-26). Effect of Prolonged Photoperiod on Light-Dependent Photosynthetic Reactions in Cannabis — International Journal of Molecular Sciences 23(17):9702
  3. Growers Network Forum thread '18/6 vs 24 hour light on' (2022-01-16). Autoflower growers compare 24/0, 20/4 and 18/6
• photoperiod (light hours)flowering, standard 12/1212 hStrong

  Initiates flowering in essentially all photoperiod cultivars tested.

  3 sources

  1. Ahrens A, Llewellyn D, Zheng Y (2023-07-10). Is Twelve Hours Really the Optimum Photoperiod for Promoting Flowering in Indoor-Grown Cultivars of Cannabis sativa? — Plants 12(14):2605
  2. Zhang M, Anderson SL, Brym ZT, Pearson BJ (2021-08-02). Photoperiodic Flowering Response of Essential Oil, Grain, and Fiber Hemp (Cannabis sativa L.) Cultivars — Frontiers in Plant Science 12:694153
  3. Moher M, Jones M, Zheng Y (2021-01). Photoperiodic Response of In Vitro Cannabis sativa Plants — HortScience 56(1):108-113
• photoperiod (light hours)flowering, 13/11 variant13 hModerate

  1.35x and 1.50x yield in two THC cultivars; cannabinoids same or higher. Cultivar-specific; trial a few plants first.

  2 sources

  1. Ahrens A, Llewellyn D, Zheng Y (2024-02-01). Longer Photoperiod Substantially Increases Indoor-Grown Cannabis’ Yield and Quality: A Study of Two High-THC Cultivars Grown under 12 h vs. 13 h Days — Plants 13(3):433
  2. Ahrens A, Llewellyn D, Zheng Y (2023-07-10). Is Twelve Hours Really the Optimum Photoperiod for Promoting Flowering in Indoor-Grown Cultivars of Cannabis sativa? — Plants 12(14):2605
• photoperiod (light hours)flowering, 14/10 variant14 hModerate

  Highest biomass when started at 14L, but static 14L lowered THC% in THC lines; near/above critical day length of some cultivars. Experimental.

  3 sources

  1. Peterswald TJ, Mieog JC, Azman Halimi R, Magner NJ, Trebilco A, Kretzschmar T, et al. (2023-02-27). Moving Away from 12:12; the Effect of Different Photoperiods on Biomass Yield and Cannabinoids in Medicinal Cannabis — Plants 12(5):1061
  2. Zhang M, Anderson SL, Brym ZT, Pearson BJ (2021-08-02). Photoperiodic Flowering Response of Essential Oil, Grain, and Fiber Hemp (Cannabis sativa L.) Cultivars — Frontiers in Plant Science 12:694153
  3. Ahrens A, Llewellyn D, Zheng Y (2023-07-10). Is Twelve Hours Really the Optimum Photoperiod for Promoting Flowering in Indoor-Grown Cultivars of Cannabis sativa? — Plants 12(14):2605
• photoperiod (light hours)flowering, 11/13 or 10/14 'finish faster'10–11 hFolklore

  Untested for faster finish; 10L delayed initiation and tended to lower cannabinoid yield. Show as folklore.

  3 sources

  1. Peterswald TJ, Mieog JC, Azman Halimi R, Magner NJ, Trebilco A, Kretzschmar T, et al. (2023-02-27). Moving Away from 12:12; the Effect of Different Photoperiods on Biomass Yield and Cannabinoids in Medicinal Cannabis — Plants 12(5):1061
  2. Oaksterdam University (cannabis trade school) web guide 'Tips for growing sativa cannabis plants indoors' (accessed 2026-10-18). Recommends 11/13 and a 10/14 finish for sativas to speed ripening (school guidance, not a trial)
  3. Dude Grows forum post 'Truth behind 11/13 in late flower?' (Happygrower11) (2021-04-30). Grower switched to 11/13 from ~week 7 of flower hoping to 'mimic nature'; anecdotal colour/terpene impressions