Viburnum xrhytidophylloides Suringar (Hybr.) (V. lantana x rhytidophyllum) – A very rare escape from cultivation. A single plant grows in spontaneous woodland near Kortrijk (Kennedybos), along with both parents. Known as an escape in the domain of the National Botanic Garden in Meise (several young plants in two locations, both more than 500 m away from the nearest cultivated plants; Ronse 2011). Also recorded self-sown in the Arboretum in Bokrijk. Other claims (see http://waarnemingen.be) require confirmation.
Palmer (1988) suggested that British records were, at least in part, produced in the wild. However, this fertile hybrid is frequently cultivated and spontaneous (bird-sown) plants more likely originate from cultivated shrubs.
Viburnum xrhytidophylloides is perfectly intermediate between both parents. Its leaves are less rugose and tomentose than those of V. rhytidophyllum. Moreover, it is only semi-evergreen and its leaves are at most three times as long as wide.
Wild records of this hybrid seem to be scarce but it is possibly overlooked although both parents definitely are much more frequent, in cultivation as well as in the wild.
Selected literature:
Mercel F. (1975) Taxonomic analysis of the hybrid between Viburnum lantana L. and V. rhytidophyllum Hemsl. (in Czech). Folia Dendrol. 2: 43-54.
Mercel F. (1978) Výsledky fenologického pozorovania Viburnum lantana L., Viburnum rhytidophyllum Hemsl. a ich Kríženca v podmienkach Arboréta Mlynaňy. (Results of phenological observation of the species Virburnum lantana L., Viburnum rhytidophyllum Hemsl and their hybrid under the conditions of the Arboretum Mlynaňy.). Folia Dendrol. 4: 91-107.
Palmer J.R. (1988) A hybrid Viburnum in West Kent. BSBI News 50: 35. [available online at: http://archive.bsbi.org.uk/BSBINews50.pdf]
Ronse A. (2011) 'Botanic garden escapes' from the living collections at the Botanic Garden. In: Hoste I. (ed.), The spontaneous flora of the National Botanic Garden of Belgium. Scripta Botanica Belgica 47: 219 p.
Vincent M.A. & Cusick A.W. (1998) New Records of Alien Species in the Ohio Vascular Flora. Ohio J. Sc. 98(2): 10-17. [available online at: https://kb.osu.edu/dspace/bitstream/handle/1811/23775/v098n2_010.pdf?sequence=1]