Forsythia koreana (Redh.) Nakai

Blossom of Forsythia koreana at Kew, 26th March 2022. Image Owen Johnson.

One of several bushes of Forsythia koreana putting on a good display of flower at Kew, 26th March 2022. Image Owen Johnson.

Flower detail of Forsythia × koreana grown at Sculpture by the Lakes, Dorset; 14th March 2022. Image Monique Gudgeon.

A 'thrum-eyed' Forsythia × koreana at Sculpture by the Lakes, Dorset, UK; 14th March 2022. Image Monique Gudgeon.

'All Gold'

An American sport of the old Korean clone ‘Ilgwang’, with yellow leaves (Dirr 2009).

'Bandal'

A variegated forsythia with a broad, irregular pale yellow margin to its leaves, fading to cream; some leaves have central splashes of variegation and some have irregular wedges. The variegation is not very stable, and fades in sun. This, and ‘Ilgwang’, are both sold in Japan under the general name ‘Fuiri Rengyo’, but differ slightly, and a plant cultivated at Brookside Gardens in Maryland was renamed as ‘Bandal’ (which means ‘half moon’ in Korean) by Carl Hahn and Barry Yinger in 1983 (Hahn & Yinger 1983).

'Bronxensis'

Of the three seedlings raised at the Boyce Thomson Institute for Plant Research in New York, from seed of Forsythia koreana received in 1928 from the Botanic Garden of the Imperial University of Tokyo. One was a dwarf sport, growing only 20–60 cm tall, with tiny leaves (2– 4.5 cm long), closely-set along the stems and edged with strikingly large and jagged teeth; the ‘pin-eyed’ flowers were primrose-yellow, but not always freely borne (Arnold Arboretum 2018; Bean 1981). Material was given to the New York Botanical Garden in the Bronx, where a later curator, Thomas Everitt, named the form Forsythia viridissima var. bronxensis in 1947, being unaware at this time of the plant’s origins.

The plant remains in commerce, though it is harder to progagate than some forsythias (DeWolf & Hebb 1971). It is now often sold under the name ‘Weber’s Bronx’ (presumably to commemorate Lillian Weber who was Everett’s Chief Horticultural Assistant in the 1940s); RHS nomenclature (RHS 2020) suggests that ‘Weber’s Bronx’ is a different clone, but there seems no historical evidence for this.

Flower detail of 'Bronxensis' at Sculpture by the Lakes, Dorset; 11th April 2022. Image Monique Gudgeon.

'Bronxensis' flowers less freely than some more recent dwarf forsythia selections. Sculpture by the Lakes, Dorset, 11th April 2022. Image Monique Gudgeon.

'Ilgwang'

An old variegated clone, grown in Japan under the general name ‘Fuiri Rengyo’. The leaves flush yellow-green and darken, particularly in the centre. It was renamed ‘Ilgwang’ (Korean for ‘sunlight’) by Carl Hahn and Barry Yinger, from a plant growing in 1983 at Brookside Gardens in Maryland, alongside the slightly different ‘Bandal’ (Hahn & Yinger 1983). Ironically, perhaps, the foliage tends to scorch in full sun.

'Kumson'

Perhaps the showiest variegated forsythia, ‘Kumson’ has leaves marked clearly and brightly with creamy-white along the veins, rather like a vegetable giraffe, though this reticulation fades with age and in shade (Dirr 2009). It was introduced from Korea under this name to the United States in 2001 by the Spring Meadow Nursery (Arrowhead Alpines 2022) and was in the UK by 2004 (Royal Botanic Garden Edinburgh 1997). This is a ‘thrum-eyed’ clone.

‘Kumson’ is likely to be same as the plant known much earlier as f. aureoreticulata (or ‘Aureo-reticulata’), and which was propagated under this name as a rare plant in Korea by Bong Choon Lee, Chang Sun Kim and Min Hyuk Kwon in 1995 (Lee, Kim & Kwon 1995), although ‘aureo-’ might imply a subtly different plant with a yellow reticulation.

Although grown primarily for its reticulated foliage, 'Kumson' shares the abundant yellow blossom of most Forsythias. Sculpture by the Lakes, Dorset, UK, 9th March 2022. Image Monique Gudgeon.

'McKCitrine'

A sport of ‘Bronxensis’ found by Dan Moore of McKay’s Nursery in Wisconsin and sold from 2005. It is comparably dwarf but its jaggedly-toothed leaves are greeny-yellow with an irregular and somewhat darker centre; the colour fades in heat but autumn colour can be burgundy-red (Dirr 2009). It is now offered for sale in the UK (RHS 2020). (In Hatch’s Cultivars of Woody Plants (Hatch 2021–2022) the difficult cultivar name appears as ‘McCitrine’ and ‘McCitrus’).

The deeply toothed young leaves of CITRUS SWIZZLE are soft yellow on 11th April 2022 at Sculpture by the Lakes, Dorset; each leaf has a slightly paler margin. Image Monique Gudgeon.

'Seoul Gold'

Leaves with an irregular yellow margin, maturing to cream, in Korea by 1993 and introduced to the United States by the Spring Meadow Nursery.

'Sunny'

A selection from Spring Meadow Nursery (USA) in 2021, with deep yellow, extra-large flowers. The trade name refers to the way the flowers spin round as they drop intact to the ground.

'Suwan Gold'

A brighter plant than ‘Seoul Gold’, developed using mass in vitro propagation in South Korea in 1994 and introduced to the United States by the Spring Meadow Nursery in 2002. The colour fades less in full sun (EurekaMag.com 2022).

The name of the Korean city where this clone originated is customarily transliterated as ‘Suwon’, but the plant seems to have been originally distributed in America as ‘Suwan Gold’.

'Variegata'

An old clone with leaves stippled white (Dirr 2009). It is represented at the UK National Collection at Sculpture by the Lakes in Dorset by cuttings taken from a plant grown under this name in the former collection at Pershore College (M. Gudgeon pers. comm.)