The genus Helianthus Linnaeus
The words or terms in red
(actually dark orange) in the text are defined in a
Plants of the Helianthus genus
(the Sunflowers) are annuals or
Their capitula are usually
radiate, and borne singly or in arrays.
Their phyllaries are persistent.
They usually have ray florets with yellow
corollas and a large number of
Their fruit is a cypsela,
usually purplish black.
There are 52 species in the genus, and the
52 are found in North America (the original habitat of the genus is the
American continent). The species (including one
that one can find in Québec are:
The number of chromosomes of the
Helianthus genus (n) is 17.
Helianthus annuus, of considerable importance because it is
is the second most used oil producing seed in the world
- Helianthus decapetalus
Helianthus divaricatus, quite rare in Québec
- Helianthus giganteus
- Helianthus grosseserratus
- Helianthus maximilianii
an adventive in Québec
- Helianthus nuttallii subsp. rydbergii
- Helianthus pauciflorus with two
- Helianthus pauciflorus subsp. pauciflorus
- Helianthus pauciflorus subsp. subrhomboide
- Helianthus tuberosus,
native in America but
introduced in Québec
- Helianthus x laetiflorus
The identification of Helianthus species has long been problematic.
Taxonomic difficulties are based on a
combination of factors, notably developmental and ecologic plasticity, the
frequency of interspecific hybridization,
and the presence of polyploidy; the
taxonomic rank of certain taxa
is still (2007) problematic.
The genus belongs to the
In classical Greek
(êlios) is the sun.
The genus scientific name refers to the flower heads that are somewhat sunlike
when blooming or because the flower heads somewhat follow the sun by day,
always turning towards its direct rays
hence the French common name Tournesol,
although Helianthus flower heads do not follow the sun across the
sky any more than other plants. And the genus common English name is just a
translation of the scientific name or vice-versa.