Why the poles exist
US stock: Most US flower lines were built from indica and sativa. Ruderalis later added autos. Kush is an indica subgroup.
High latitude: Northern and mountain populations stay mixed so some plants survive any given year.
Low latitude: Tropical populations are more uniform because seasons repeat.
Today: Almost every commercial pack is a hybrid sitting somewhere between the two ends.
Indica in the room
Origin
Central Asia between about 25 and 35 degrees, where weather swings hard
Frame
Short, compact, with wide dark leaves that can pick up purple
Buds
Tight, wide, and heavy rather than long spears
Clock
Often 6 to 9 weeks of flower. Height often 2 to 6 ft
Resin past
Many were bred for hash, then later smoked as whole flower in the West
Sativa in the room
Origin
Equatorial and near-equatorial lines from the Americas, Africa, India, and Thailand
Frame
Tall Christmas-tree form, long internodes, narrow serrated blades
Buds
Long and sausage-shaped in strong sun. Under weak indoor light they run thin and may not fill
Clock
Often 8 to 15 weeks. Outdoor height can reach 5 to 25 ft
Season
They need a long finish and often miss frost in short northern summers
Side-by-side cues
Nodes
Indica keeps short gaps between leaves. Sativa stretches
Color
Indica runs dark green to purple. Sativa runs pale to medium green
Odor
Indica is often pungent or skunky. Sativa is often sweet to spicy
Effect language
Growers still say indica leans heavy and sativa leans racy, but hybrids blur that map