Scientifically (and legally), there is no difference between Indica and Sativa; all cannabis plants are considered to be Cannabis sativa L..
In practice, the differences between Indica and Sativa are many and varied. Generally the terms are used to describe broad categories which indicate a particular strain’s place in the the ‘spectrum’ of cannabis. There are a multitude of different growth-patterns, qualities and effects within this spectrum and the differences between Indica and Sativa are largely due to the fact that cannabis displays a remarkable ability to adapt to a wide range of different environments.
Since all branches of the cannabis family tree can interbreed freely (including industrial hemp and Cannabis ruderalis J.), some botanists consider all forms of the plant to be members of a single polymorphic species.
Cannabis indica L.
Most Indica varieties come from central Asia and the Indian subcontinent – Afghanistan, Pakistan, northern India, Tibet, Nepal, and so on.
Indicas are compact and stocky, with dense, heavy, fragrant buds. Cannabis plants produce nodes at regular intervals along their stems, and these nodes are the sites at which leaves, branches and flowers (buds) form. Indica buds tend to grow in dense clusters around the nodes of the stem and branches, with relatively short spaces (known as internodal gaps) between each cluster.
Indicas are the faster flowering varieties, and usually have a flowering time of 45 to 60 days.
Indicas gain height quite rapidly once flowering begins, but they shouldn’t grow out of control in normal circumstances. An Indica may be expected to increase its vegetated height by a factor of 50-100% during its flowering period.
The effect of Indica is generally classified as a ‘stone’, meaning that it is more centred on the body. Indicas may enhance physical sensations such as taste, touch and sound. The Indica effect is noted for being physically and mentally relaxing and it may be soporific in larger doses.
Cannabis sativa L.
Sativas generally originate in the equatorial regions – Thailand, southern India, Jamaica, Mexico, and so forth .Given the same conditions, Sativas grow taller than Indicas. Sativa buds tend grow larger than Indica, as they run along the length of a branch instead of clustering around the nodes. However, they will usually weigh less than Indica when dry, due to their lower density. Sativa buds also tend to have a less striking odour, both when growing and when dry.
A major difference between Indicas and Sativas is that Sativas take longer to flower. They will usually need between 60 and 90 days to finish blooming. However, they need less time for vegetative growth prior to flowering than Indicas do, so the overall time required for Sativas is about the same as for Indicas (and sometimes less in terms of ‘light hours’).
Sativas can increase in height very rapidly once flowering begins and will often continue to gain height throughout their blooming phase. It is normal for Sativas to gain 200-300% (or even more) of their vegetative height while flowering.
In tropical regions, the days tend to be relatively short – close to 12 hours long all year round – so Sativas are adapted to grow and flower at the same time instead of having distinct vegetative and blooming stages as Indicas do. In a 12/12 indoor flowering cycle, Sativas will grow and flower at the same time as they would in their native environment.
Despite their lower weight and potentially longer flowering time, Sativas are valued by many growers for their ‘high’ effect. This high may be characterised as cerebral, energetic, creative, giggly or even psychedelic. It is less overpowering than the Indica ‘stone’, and less likely to send the user to sleep.