Classifying cannabis strains

The current classifications of cannabis rely on morphologic traits or chemical characteristics.  These classifications can be very confusing, especially in with the vast amount of hybridization that has occurred in the cannabis place over the last century.  A typical user will classify the various strains as “sativa” or “indica” when in fact they could be both C. indica strains.  As well, a plant that appears to be a C. sativa strain, with long thin leaves, may be in fact a hybrid. For these reasons, chemical characteristics are much more valuable to use when classifying the different types of cannabis.

              Morphological classification of cannabis consists of grouping cannabis by their physical traits.  The C. sativa is thought to originate from the spread of plants from Asia and the Himalayas down to northern Africa.2 This strain tends to have lighter green leaves that are longer and thinner in order to adapt to hotter environments.  C. sativa is usually seen to be taller and have a sparse number of flowers.1 It is the primary strain used in industrial hemp. The origins of C. indica are thought to be from the spread of plants near central Africa, Afghanistan, and China.  These were also the plants that eventually spread to Latin America.2 C. indica strains tend to have a bushier appearance. The leaves are shorter and broader than those of the C. sativa strain.3  While classifications based on phenotypes such as these seem straightforward, the dioecious nature of cannabis causes hybridization among strains easily.2 What was once classified as a C. sativa may contain high amounts of THC and find genetic links to C. indica ancestors.  For this reason, classification by chemical characteristics is much more accurate.4

              Hybridization among the different strains of cannabis has been happening ever since it has been used and cultivated by humans.  By crossing male and female plants of different strains, the desirable chemical traits, such as plants high in THC, are easy to create.  In fact, most strains that are found in the medicinal market are a hybrid of C. sativa and C. indica.  These chemical differences make it almost impossible to classify by phenotype alone.4 Instead. The current and most accurate ranking system follows a numeric system.  Type 1 cannabis plants are high in THC and low in CBD.  Type 3 plants are high in CBD and low in THC. Type 3 plants are a combination that show different THC:CBD ratios.4 Using this classification, a pure C. sativa would fall into type 3 while a C. indica would be a type 1.  Hybrids of the two types would be a type 2.4 This is a much more accurate way of classification because the actual chemical constituents show what strain may or may not be dominate in a certain plant based on THC:CBD ratios.

              The original strains of cannabis plants, C. sativa and C. indica, have been so vastly hybridized that classifying a single plant by its physical appearance is nearly impossible.  By looking at its chemical composition, specifically the THC:CBD ratio, the classification can be much more accurate and denote which strain may be dominant. The three types of classifications, type 1, type 2, and type 3, give more insight to the actual composition of the plant than by just comparing such physical features as leaf shape and plant height.


  1. Cervantes, J. The Cannabis Encyclopedia: The Definitive Guide to Cultivation & Consumption of Medical Marijuana. Van Patten Publishing; 2015.
  2. Punja ZK, Rodriguez G, Chen S. Assessing genetic diversity in Cannabis sativa using molecular approaches. In Cannabis sativa L.-Botany and Biotechnology 2017 (pp. 395-418). Springer, Cham.
  3. ElSohly MA, Lata H, Chandra S. Cannabis Sativa L.–Botany and Biotechnology. Springer; 2017.
  4. Cisar J. Genomic and strain diversity. MCST608 Lecture Slides. University of Maryland School of Pharmacy.

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