Like all annuals, cannabis grows in three phases (Figure 1) and many more sub-phases, or stages. Each has its own demands that require specific care and supervision, including nutrition, lighting, climate, irrigation, pruning and so forth. Meeting each of these demands is essential for maximizing plant potential—achieving the most vigorous possible growth, the most bountiful possible yield and the optimal cannabinoid profile, depending on the strain.
Figure 1. Cannabis life cycle.
Maintenance during propagation: caring for clones
Rather than growing plants from seed, most cannabis growers start with clones. Raising a crop from clones preserves the specific strain and ensures consistent flavor, aroma and psychoactive or therapeutic effects. While clones can develop into vigorous plants that produce high-quality buds, they are delicate in their early stages and require careful management to prevent pests, diseases and poor growth.
Maintenance during propagation: caring for clones
Rather than growing plants from seed, most cannabis growers start with clones. Raising a crop from clones preserves the specific strain and ensures consistent flavor, aroma and psychoactive or therapeutic effects. While clones can develop into vigorous plants that produce high-quality buds, they are delicate in their early stages and require careful management to prevent pests, diseases and poor growth.
Select healthy clones and maintain sterility
Maintaining clones starts with choosing healthy ones. Always procure clones from a reputable supplier to ensure genetic stability and plant vigor. Inspect each one carefully. Look for vibrant green leaves, sturdy stems and an overall healthy appearance. Avoid any that appear wilted, discolored or infested, because they can compromise the entire grow.
Cleanliness and sterility are equally important. Young plants are particularly vulnerable to pathogens,[1] so follow strict hygiene practices. Sterilize tools and trays between uses to reduce the risk of spread if diseases are present.
Environmental maintenance
- Climate: Keep the air temperature at ~68–73°F (20–23°C) and humidity at 65–75%.[2] Use fans and ventilation to promote gentle air circulation and reduce the risk of mold or mildew.
- Light: Maintain an 18/6 photoperiod (18 hours of light, 6 hours of darkness) and a photosynthetic photon flux density (PPFD) of 200–300 µmol/m²/s.[3]
- Nutrients: Unless clones show signs of stress, delay fertilization until the second week. Start with a nitrogen (N) concentration of 250–350 ppm. In the third week, increase it to 450–600 ppm. If using Cali Pro Grow A and B, Emerald Harvest’s two-part nutrient series, feed 0.5 mL/L of each per week.
- Irrigation: Water lightly and frequently to keep roots moist but not waterlogged.
Transplanting clones
Successful transplantation—the first stage of the vegetative phase—depends on a strong root system. In hydroponics, clones are ready once their roots can reach the nutrient solution.[4]
To avoid transplant shock, help acclimatize the plants by hardening them off: Either increase the light intensity during the final week of propagation or use a low-light area during early veg, gradually increasing the intensity.[5]
When transplanting, increase Cali Pro Grow A and B to 0.75 mL/L each per week.
Transplanting clones
Successful transplantation—the first stage of the vegetative phase—depends on a strong root system. In hydroponics, clones are ready once their roots can reach the nutrient solution.[4]
To avoid transplant shock, help acclimatize the plants by hardening them off: Either increase the light intensity during the final week of propagation or use a low-light area during early veg, gradually increasing the intensity.[5]
When transplanting, increase Cali Pro Grow A and B to 0.75 mL/L each per week.
Maintenance during the vegetative phase
Clones should reach the vegetative phase by the end of the third week of propagation. This second phase of the cannabis life cycle is when the plant focuses on rapid structural growth to support future bud formation. During this stage, plants grow several inches per week, produce fan leaves, thicken their stems and continue developing their roots.
Maintenance during the vegetative phase
Clones should reach the vegetative phase by the end of the third week of propagation. This second phase of the cannabis life cycle is when the plant focuses on rapid structural growth to support future bud formation. During this stage, plants grow several inches per week, produce fan leaves, thicken their stems and continue developing their roots.
Environmental maintenance
- Climate: Keep the temperature at ~77–86°F (25–30°C)[6] and humidity at 60–75%.[7] Continue maintaining good air circulation.
- Light: Maintain a long photoperiod—18 hours, or even up to 24 hours—to provide ample light for maximizing photosynthesis[8] and a PPFD of ~400–600 µmol/m²/s.[9], [10]
- Nutrients: Fertilize with a nutrient solution that is relatively high in N, which is appropriate to the veg phase.[11] One study found that a nutrient solution containing 160–200 mg of N, 30 mg of phosphorus (P) and 60 mg of potassium (K) per liter was ideal during veg.[12] Aim for an EC of 1.0–2.5[13] and a pH of 5.8–6.3. All base nutrients supply essential nutrients, but they often contain insufficient calcium, vital for strong cell walls. Most fertigation programs recommend 150–300 ppm of calcium—lower in early veg and higher during flowering. Because calcium interacts with P, it should be supplemented separately with a product like Cal-Mag. Growers using coco coir must be particularly mindful of calcium deficiency.
- Irrigation: Frequency and volume depend on the strain, hydroponic system, growing medium, environment and other factors. Adjust based on the substrate’s moisture curve, plant transpiration and runoff EC.
Topping and training
Veg is the phase to begin pruning and training to shape the plant structure. Topping and low-stress techniques like sea of green and screen of green[14] create a uniform canopy, improving light distribution and penetration, airflow and nutrient use. These methods are particularly important when managing high plant densities.
Maintenance during the flowering phase
The flowering or “bloom” phase, when plants develop the juicy buds consumers desire, is the most anticipated.
Photosensitive strains (photos)[15] enter flowering when exposed to at least 12 hours of uninterrupted darkness.[16] This sudden change in photoperiod is called “flipping” and should occur once the plants have reached their ideal height, typically around 24–36 inches.[17] Photos often undergo rapid stem elongation after flipping—the “stretch”[18] period—so flipping while the plant is still relatively short allows grow rooms to accommodate this expected growth. Most mature within 6–9 weeks, depending on the strain.[19]
The flowering or “bloom” phase, when plants develop the juicy buds consumers desire, is the most anticipated.
Photosensitive strains (photos)[15] enter flowering when exposed to at least 12 hours of uninterrupted darkness.[16] This sudden change in photoperiod is called “flipping” and should occur once the plants have reached their ideal height, typically around 24–36 inches.[17] Photos often undergo rapid stem elongation after flipping—the “stretch”[18] period—so flipping while the plant is still relatively short allows grow rooms to accommodate this expected growth. Most mature within 6–9 weeks, depending on the strain.[19]
Environmental maintenance
- Climate: Lower humidity to 50–55%[20] and reduce the temperature. One study found flowering plants exposed to a daytime temperature of 31°C and a nighttime temperature of 27°C had lower cannabinoid concentrations than those grown at 25°C and 21°C during day and night, respectively.[21] Continue providing good air circulation. However, avoid direct airflow on plants, as this can cause wind stress.
- Light: Maintain a 12-hour (or shorter) photoperiod to induce flowering in photos. Gradually increase the PPFD; one study found that cannabis yields rose linearly with PPFD increases up to 1,800 µmol/m²/s.[22]
- Nutrients: Use “bloom” formulations designed for the flowering phase, when cannabis needs relatively less N and more P and K to fuel bud development. Research shows that the ideal nutrient levels are 160–230 mg/L of N, 40–80 mg/L of P[23] and 60 mg/L of K.[24] Raise the EC to 2.0–4.0.[25]
- Irrigation: Meet the crop’s increased water demands without over- or underwatering. Consider reducing irrigation 2–3 weeks before harvest to induce drought stress, which has been shown to increase THCA and CBDA concentrations.
Prune early—but only if necessary
Most pruning should take place during veg. However, light pruning during early flowering can help shape the canopy, improve light penetration and remove needless lower branches. Avoid heavy pruning later in flowering, as it can stress the plant and redirect energy away from bud production.
Conclusion
Proper maintenance during each phase of the cannabis life cycle gives plants the best chance to yield abundant, flavorful, potent buds. By understanding the stages and how to meet their unique needs, growers can set their plants and operation up for a successful harvest.
Emerald Harvest Team
[1] Bioengineer. 2025. “Study Uncovers the Reasons Behind Young Plants’ Susceptibility to Disease.” Published September 6. https://bioengineer.org/study-uncovers-the-reasons-behind-young-plants-susceptibility-to-disease/.
[2] Adhikary, Dinesh, Manoj Kulkarni, Aliaa El-Mezawy, et. al. 2021. “Medical Cannabis and Industrial Hemp Tissue Culture: Present Status and Future Potential.” Frontiers in Plant Science 12: 627240. https://doi.org/10.3389/fpls.2021.627240.
[3] Ibid.
[4] Langenfeld, Noah James, and Bruce Bugbee. 2022. “Germination and Seedling Establishment for Hydroponics: The Benefit of Slant Boards.” PLoS One 17 (10): e0275710. https://doi.org/10.1371/journal.pone.0275710.
[5] Morrow, Kenneth. 2021. “Cannabis Propagation: 8 Tips.” Cannabis Business Times, December 7. https://www.cannabisbusinesstimes.com/columns/tomorrow-in-cannabis/article/15694023/cannabis-propagation-8-tips.
[6] Chandra, Suman, Hemant lata, Ikhlas A. Khan, and Mahmoud A ElSohly. 2009. “Photosynthetic Response of Cannabis sativa L. to Variations in Photosynthetic Photon Flux Densities, Temperature and CO2 Conditions.” Physiology and Molecular Biology of Plants, 14 (4): 299–306. https://doi.org/10.1007/s12298-008-0027-x.
[7] Chandra, Suman, Hemant Lata, and Mahmoud A. ElSohly. 2020. “Propagation of Cannabis for Clinical Research: An Approach Towards a Modern Herbal Medicinal Products Development.” Frontiers in Plant Science 11: 958. https://doi.org/10.3389/fpls.2020.00958.
[8] Ibid.
[9] Rodriguez-Morrison, Victoria, David Llewellyn, and Youbin Zheng. 2021. “Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment.” Frontiers in Plant Science 12: 646020. https://doi.org/10.3389/fpls.2021.646020.
[10] Llewellyn, David, Scott Golem, Elizabeth Foley, Steve Dinka, A. Maxwell P. Jones, and Youbin Zheng. 2022. “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. https://doi.org/10.3389/fpls.2022.974018.
[11] Chandra, Suman, Hemant Lata, and Mahmoud A. ElSohly. 2020. “Propagation of Cannabis for Clinical Research: An Approach Towards a Modern Herbal Medicinal Products Development.” Frontiers in Plant Science 11: 958. https://doi.org/10.3389/fpls.2020.00958.
[12] Kpai, Patrick Yawo, Oluwafemi Adaramola, Philip Wiredu Addo, Sarah MacPherson, and Mark Lefsrud. 2024. “Mineral Nutrition for Cannabis sativa in the Vegetative Stage Using Response Surface Analysis.” Frontiers in Plant Science 15: 1501484. https://doi.org/10.3389/fpls.2024.1501484.
[13] Cannabis Sustainability Work Group. 2022. “Cannabis Environmental Best Management Practices Guide 2022.” Accessed September 10, 2025. https://sbg.colorado.gov/sites/sbg/files/documents/Cannabis%20Environmental%20Best%20Management%20Practices%20Guide%202022_FINAL_0.pdf.
[14] Often abbreviated SOG and SCROG, respectively.
[15] Auto-flowering strains (autos) will flower on their own and do not require a reduction in photoperiod.
[16] Chandra, Suman, Hemant Lata, and Mahmoud A. ElSohly. 2020. “Propagation of Cannabis for Clinical Research: An Approach Towards a Modern Herbal Medicinal Products Development.” Frontiers in Plant Science 11: 958. https://doi.org/10.3389/fpls.2020.00958.
[17] Morrow, Kenneth. 2024. “Size Matters: The Case for Short Cannabis Plants.” Cannabis Business Times, March 11. https://www.cannabisbusinesstimes.com/containers-growing-media/vertical-grow-cannabis-cultivation-technique/article/15686978/size-matters-the-case-for-short-cannabis-plants.
[18] Alden, Michael J., and James E. Faust. 2024. “Cultivation Strategies to Modify Biomass Partitioning and Improve Yield in Controlled-Environment Production of High-Cannabidiol Cannabis (Cannabis sativa L.).” HortScience 59 (10): 1511–1519. https://doi.org/10.21273/HORTSCI17968-24.
[19] Chandra, Suman, Hemant Lata, and Mahmoud A. ElSohly. 2020. “Propagation of Cannabis for Clinical Research: An Approach Towards a Modern Herbal Medicinal Products Development.” Frontiers in Plant Science 11: 958. https://doi.org/10.3389/fpls.2020.00958.
[20] Ibid.
[21] Holweg, Mexximiliaan M. S. F., Thomas Curren, Aurora Cravino, et. al. 2025. “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. https://doi.org/10.1016/j.envexpbot.2025.106085.
[22] Rodriguez-Morrison, Victoria, David Llewellyn, and Youbin Zheng. 2021. “Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment.” Frontiers in Plant Science 12: 646020. https://doi.org/10.3389/fpls.2021.646020.
[23] Bevan, Lewys, Max Jones, and Youbin Zheng. 2021. “Optimisation of Nitrogen, Phosphorus, and Potassium for Soilless Production of Cannabis sativa in the Flowering Stage Using Response Surface Analysis.” Frontiers in Plant Science 12: 764103. https://doi.org/10.3389/fpls.2021.764103.
[24] Saloner, Avia, and Nirit Bernstein. 2022. “Effect of Potassium (K) Supply on Cannabinoids, Terpenoids and Plant Function in Medical Cannabis.” Agronomy 12 (5): 1242. https://doi.org/10.3390/agronomy12051242.
[25] Cannabis Sustainability Work Group. 2022. “Cannabis Environmental Best Management Practices Guide 2022.” Accessed September 10, 2025. https://sbg.colorado.gov/sites/sbg/files/documents/Cannabis%20Environmental%20Best%20Management%20Practices%20Guide%202022_FINAL_0.pdf.
