Growing Your Own Cannabis, Part 3: Monitoring Plant Health & Harvesting

Written by Lance Griffin

You have learned about cannabis lighting, grow techniques, and nutrients, and you’re ready to get your hands dirty. This article discusses monitoring your plants’ health, and harvesting the fruits (or flowers) of your labor.

Monitoring Plant Health

Throughout cannabis cultivation, carefully inspect plants to ensure optimal health. A magnifying glass or lens is critical. Watch for:

  • Spider mites: microscopic arachnids that cause small spots on leaves and stunt growth.
  • Fungi: fungal outbreaks can cause roots to rot and leaves to wilt, turn yellow, or spot white. There are at least 88 types of fungi that can affect cannabis. Humidity can facilitate fungal growth and should be carefully controlled by indoor growers; tools are available to measure humidity.
  • Disease: may be caused by fungal pathogens as with pythium root rot, but also include viruses such as tobacco mosaic virus. Signs of disease include poor growth, dead leaf tips,and mosaic patterning or spotting on leaves.

To prevent these issues, maintain cleanliness and circulation. Be aware of erroneous conditions, such as excess or insufficient moisture, nutrient overload, and improper lighting. If plants sag, fail to grow, or demonstrate discoloration, there is a problem. [1] Nip it in the bud.


Flowering requires 12 hours of darkness and 12 hours of light. During this stage, female plants deliver flowers that bloom, swell, and produce resin.

The ideal window to harvest flowers is roughly 5 to 7 days. At this point,trichomes crowd the leaves. The pistils will fall back and change color from white to shades of red and brown.[1]

Determining peak time to harvest can be more of an art than a science.Check the resin glands on the flowers: when ready, they will be fully formed (stalk with a gland head) and creamy white to transparent amber. Use your magnifying lens. Early on, glands are clear; they progress to late harvest as the color ambers. Changes may not be uniform. Harvesting too early or too late may negatively affect the chemical profile of the final product. [1-2]

Most growers stop fertilization 7 to 10 days before harvesting to avoid affecting taste with residual chemicals.Furthermore,growers rinse/flush plants and soil with pure water to remove any chemicals used.The use of a specialized flushing agent (rather than water) may permit fertilization up to three days prior to harvest. [1] That said, there are a few dissenting voices that question the validity of the flushing practice.

Sever the plant at the base.Your cannabis plant is now harvested. Congratulations! But, you’re not quite done.

Trimming and Curing

Trim off the leaves and leaf stems with a pair of trimming scissors. Hang the trimmed flowers in an area with moderate humidity and adequate ventilation at 65-75°F. Some DIYers use a closet.Monitor for a week or more until dry (stems should snap, not bend). Continue to monitor for mites and other unwanted guests. [1]

Cure the flowers for several days to several weeks in a sealed container. Lift the lid several times daily and sift the buds to release excess moisture and evade mold. The weight of a fully dried flower bud may be 75% less than its weight at harvest.[1]

There you have it. Growing your own cannabis is easy to start and difficult to master.  Take these tips with you on the journey, and you’ll be surprised at how much fun you have.


  1. Cervantes, J. Marijuana Horticulture: The Indoor/Outdoor Medical Grower’s Bible(L. Meyer, Ed.). 2006, Van Patten Publishing.

Clarke, R. C. Maturation and Harvesting of Cannabis. Marijuana Botany: An Advanced Study: The Propagation and Breeding of Distinctive Cannabis. 1981. Retrieved from Google Books

About the author

Lance Griffin


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