The Onagraceae are a
family of
flowering plants known as the willowherb family or evening primrose family. They include about 650 species of
herbs,
shrubs, and
trees[4] in 17 genera.[5] The family is widespread, occurring on every continent from
boreal to
tropical regions.
The family includes a number of popular
garden plants, including evening primroses (Oenothera) and
fuchsias (Fuchsia). Some, particularly the willowherbs (Epilobium), are common
weeds in gardens and rapidly colonize disturbed habitats in the wild. One such species is
fireweed (Chamaenerion angustifolium).
The family is characterised by
flowers with usually four
sepals and
petals; in some genera, such as Fuchsia, the sepals are as brightly coloured as the petals.
The
seeds are generally very small. In some genera, such as Epilobium, they have tufts of hairs[6] and are
dispersed on the wind. In others, such as Fuchsia, the seeds develop in juicy
berries dispersed by animals. The
leaves are commonly opposite or whorled, but are spirally arranged in some species; in most, they are simple and lanceolate in shape. The
pollen grains in many genera are loosely held together by
viscin threads. Most
bees cannot collect it, and only bees with specialized morphologies can effectively pollinate the flowers; nearly all bee taxa that visit the flowers are
oligoleges specialized on the family Onagraceae.
The family was named after the genus Onagra (now known as Oenothera) in 1836 by
John Lindley in the second edition of A Natural System of Botany.
Several genera are synonymized in the classification presented above, in particular Calylophus and Gaura, which have both been absorbed into Oenothera but appear often in the literature as belonging to the previous genera.