Two species of forsythia are at the heart of the selected forms and garden hybrids:
Forsythia suspensa and
F. viridissima. "These two species are, as it were, the founder-members of the forsythia family" writes
Alice Coats; they were the earliest species brought into Western gardens from the Far East and they have each played a role in the modern garden shrubs.
Forsythia suspensa, the first to be noticed by a Westerner, was seen in a Japanese garden by the botanist-surgeon
Carl Peter Thunberg, who included it (as a lilac) in his
Flora Japonica 1784. Thunberg's professional connections lay with the
Dutch East India Company, and
F. suspensa reached Holland first, by 1833. In England, when it was being offered by
Veitch Nurseries in Exeter at mid-century, it was still considered a rarity. Not all the varieties of
suspensa are splaying and drooping, best seen hanging over a retaining wall; an erect form found by Fortune near
Peking in 1861 was for a time classed as a species—
F. fortunei. as have
F. ×
intermedia Week End 'Courtalyn' and
F. Marée d'Or 'Courtasol'. About the time of the First World War further species were discovered by plant hunters in China:
F. giraldian (found in Gansu, 1910) and
F. ovata (collected from seed in Korea by
E.H. Wilson) have been particularly useful as seed parents in 20th-century American crosses. ==Cultivation==