After spending an afternoon looking for info about cultivation environments and plant activity specific to each growth stage for medical marijuana, I discovered information was either scattered among various pages and sources, or not particularly newbie-friendly. So, I have attempted to aggregate the basic growth activity and recommended environment per stage into one document. (It’s a long read, but hopefully will save you some research time; there is an infographic attached to this blog that sums up this blog.)
Here’s the deal: Cannabis’ life cycle has 4 main growth stages: germination, seedling, vegetative, and flowering. During each stage, your plant will require specific nutrients, growing mediums and environments in order to achieve the highest yield possible.
Stage Activity & Duration: Germination marks the beginning of your plant’s life cycle. The duration of this stage varies by strain, however most strains require approximately 3 – 8 days to complete germination. There are three key components to this stage: moisture, warmth, and darkness. Germination comes to an end when the seed sprouts, splitting the seed coating, and a tap root emerges.
Temperature & Light: The seeds’ environment should be kept around 75 - 85 °F with room humidity levels around 50%.
Growing Medium: During this time, your young plant will be very sensitive to its environment. Ideally, seeds should be placed in a warm, dark and moist place. It’s common to initiate germination by soaking seeds between wet paper towels or peat moss. Personally, I prefer peat moss as it allows you to transfer the young plant directly into soil with minimum shock. A light, loose soil with perlite is an ideal growing medium for germinating and the seedling stages.
Stage Activity & Duration: Once the seed coating splits, a tap root emerges, and embryonic leaves develop. A second pair of leaves will emerge, differing from the embryonic leaves. The second pair of leaves develop opposite of one another and usually have a single blade. The first set of leaves and root system develop in this critical growth stage. A healthy root system is the key to a healthy plant and a high yield; the root system is responsible for the uptake of vital nutrients critical to the plant’s growth. Typically, this stage lasts 4 – 6 weeks. As your plant progresses through this stage a new set of leaves will start to develop; each leaf will have 3 blades and will be larger than the second pair.
Temperature & Light: Your seedling is happiest in a humid & warm environment. Optimal temperature range is 70 – 85 °F with humidity levels around 70 – 80%. Typically, an 18 / 6 light cycle is observed.
Growing Medium: Using a high porosity growing medium during this stage is crucial to the plant’s growth and development. High porosity growing mediums allow your plant to easily drain excess water and provide the root system enough room to grow–accessing oxygen easily.
Water: During this stage “soft” water is recommended because tap is often treated with chemicals that could damage your seedling. Soft water has a pH of 5.5 - 6.5, which is slightly acidic. If you use tap water to water your plants, allow the water to stand for 24 hours. By doing so, chemicals will evaporate and the water will reach room temperature-reducing the stress on your plant as you water.
Stage Activity & Duration: During the vegetative stage your plant will begin to grow, well, like a weed. Vegetative state begins when your plant produces approximately 7 sets of true leaves, with an 8th leaf growing from the tip. During this stage the plant directs its energy to growing leaves and stems. This stage can last anywhere from 4 – 6 weeks with indoor strains, however cannabis can remain in the vegetative state until you change the light cycle to 12/12. The longer you keep your plant in this state, the larger it grows and the higher yield it produces.
Temperature & Light: Growing room temperatures should be kept between 70-85 °F. Remember there may be a slight drop in temperature at night (when the lights are off). Optimal room humidity levels range from 50 – 80%. Recommended light cycles during this stage vary based on strain between either 18/6 or 20/4 for optimal growth.
Growing Medium & Nutrients: There are 3 main macronutrients vital to your plant’s health: Nitrogen (N), Phosphorous (P), and Potassium (K). Fertilizers containing these macronutrients are commonly added to growing mediums during this stage of growth. Nitrogen plays a key role in the plant’s ability to grow stems and leaves. Fertilizers often list the ratio of nitrogen, phosphorous, and potassium; the ideal N:P:K ration is 2:1:1. It’s important to note that an overabundance of nutrients and fertilizers can be harmful to your plant’s wellbeing. If you choose to add nutrients to your water supply do not add the full recommended dose; instead, start with ¼ of the recommended dose and slowly increase the amount until you find the dose that works for you.
Water: The frequency of your watering regimen depends on your growing medium. If your growing medium contains perlite or clay pebbles you will need to water you plants more frequently than dense, water-retentive growing mediums. If soil is damp to the touch then you do not need to water.
Stage Activity & Duration: The flowering stage is the final growth state in your plant’s growth cycle. During this stage, floral clusters develop and buds are produced, cannabis sex characteristics become evident, large shade leaves fall off as your plant focuses its’ energy toward developing floral clusters. It is critical to remove all male cannabis plants from your grow room and away from the female plants in order to prevent pollination. It is also important to note that cannabis plants can exhibit both male and female sex characteristics. These hermaphrodites should also be removed from your female plants. Most strains need 2 – 3 months in the flowering stage before they are ready to harvest. Pure indicas usually finish flowering after 8 weeks and pure sativas usually finish flowering around 12 – 14 weeks. When about 80% of the hairs (known as pistols) are orange or amber, the buds are ready for harvest.
Temperature & Light: Once your plant has reached the desired size (during the vegetative stage) and you are ready to induce flowering, change your light cycle to 12/12. During the “dark” cycle it is critical plants be kept in complete darkness; if you need to garden during this cycle green light bulbs are recommended as they will not harm your plants. Personally, I try to do all my gardening during the 12 hours of light so the plants can be kept in total darkness during the 12 hour dark cycle. Be sure to place the lights approximately 24 inches from the plants & buds to prevent overheating. Heat during this phase can stress the plant and potentially affect the quality of your yield. Ideally, your grow room temperature should remain within a range of 70 – 85 °F. Growing room humidity should be kept at or below 45% to prevent your buds from molding.
Growing Medium & Nutrients: Nitrogen and light exposure take a back-seat during this stage of growth. Instead, your plant will seeks phosphorous and potassium as the main source of fuel for the flowering process. Regularly checking the pH of your growing medium is important during this stage (generally, a pH of 6.5 is ideal for flowering) as an imbalanced pH level can also affect the yield.
Water: Water your plants as needed. Approximately 1 – 2 weeks before you are ready to harvest the buds, begin flushing your plants with pH’ed water to leach any excess nutrients (an overabundance of nutrients within your growing medium can cause your buds to cause a chemical-like taste).
Okay, that wraps up the growth stages–all in one blog. Let me know if this has been helpful. Feedback is always appreciated.