The gentian family contains about 87 genera and over 1600 species.  The family is classified in the angiosperm order Gentianales, and belongs to the Asterid I clade and the subclass Asteridae.  What is a gentian?

Typical characteristics for gentians are:

- plants glabrous (no simple or glandular hairs)

- opposite, simple, entire leaves

- leaf venation with a prominent midrib and few, basally divergent and curved secondary veins

- no stipules (but sometimes with an interpetiolar line or a low, interpetiolar sheath)
flowers actinomorphic (radially symmetric, rarely not)

- flowers bisexual (with both stamens and pistil in each flower)

- sepals fused at least at the base  

- petals fused at least at the base (sympetalous)

- petals often very colorful and large

- petal lobes contorted (twisted) to the right in bud

- stamens inserted in the corolla tube (if you pull a stamen off, the petals come too)

- ovary superior (hypogynous flowers)

- ovary bicarpellate (the pistil is formed by two carpels)

- chemicals present: seco-iridoids and xanthones (alkaloids are absent)

(more about gentians' morphology and anatomy)

How to distinguish a gentian (Gentianaceae) using field characters from other similar and related plant families:
(Note that there are some exceptions to these 'rules')

from Apocynaceae (and Asclepiadaceae, now included in Apocynaceae): gentians lack (vs. have) latex [milky sap]

from Bignoniaceae, Gesneriaceae, and Scrophulariaceae s. lat.: gentians have as many stamens as petals (vs. fewer stamens than petals), the flowers are actinomorphic [radially symmetric] (vs. often zygomorphic [bilateral]), and the leaves are glabrous (vs. often hairy)

from Gelsemiaceae: gentians have homostylous (vs. heterostylous) flowers, simple or bilobed stigmas (vs. 4-branched stigmas/styles) 

from Loganiaceae: gentians have petals lobes contort in bud (vs. valvate or imbricate [irregularly overlapping or not overlapping]), no hairs (vs. with) on the inside of the corollas

from Rubiaceae: gentians have superior (vs. inferior [inserted in the flower stalk below the flower]) ovaries and no (vs. with) interpetiolar stipules

from Solanaceae: gentians have opposite (vs. alternate) leaves

© Lena Struwe, 2002