What are trichomes on cannabis?

"Trichomes are the resinous glands on the cannabis flowers of the female cannabis plant. They produce cannabinoids like THC and CBD that provide a spectrum of relief.

Trichomes are found on many plants and can be a response to a number of environmental factors, including damage from light, insects, animals, and the spreading of fungus. Cannabis trichomes vary in shape and size, and are best viewed through a 25x microscope.[1]

Cannabis cultivators use trichome vitality to gauge the maturity of the plant.[2] Although every strain varies, the glands of the trichomes begin with clear or amber heads, and will begin to appear murky and opaque as the glands reach their maximum potency. As the trichomes become cloudier and begin to droop, the cultivator knows the plant has reached maturity, and that the trichomes will begin to lose potency as the THC breaks down to CBN (cannabinol) in a chemical process known as oxidation."[3]

[1] - http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4080826/

[2] - http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3337187/

[3] - http://www.alchimiaweb.com/blogen/harvest-marijuana-plants-trichome-ripeness/