1. Gaillardia x grandiflora Van Houtte (= G. aristata Pursh x G. pulchella Foug.) (hort.) – A rare but locally naturalised escape from cultivation. The invasion history of Gaillardia x grandiflora in Belgium is rather well-documented. It was first collected in coastal dunes near St.-Idesbald in 1953 (close to residences and obviously escaping from nearby gardens). In 1955 it was already firmly established between St.-Idesbald and Koksijde (sandy road verges, ruderalized seadunes,…). Subsequently further spreading eastwards along the Belgian coast: Oostduinkerke (locally very abundant), Nieuwpoort,… (Verloove 2002). More recently also recorded in Middelkerke (Verloove 2006).
Gaillardia x grandiflora grows is dry, sun-exposed habitats. Initially is was chiefly confined to vacant lots in residential areas (often ruderalized and of a lesser concern) but in the past decades Gaillardia x grandiflora has penetrated in several nature reserves (for instance in Ter Yde and Groenendijk in Oostduinkerke, Warandeduinen in Middelkerke, etc.) and is regarded as an invasive alien. It now occurs in calcareous grasslands and is locally eradicated.
The populations from the Belgian seadunes were first ascribed to the annual Gaillardia pulchella. However, they are obviously perennial and more closely related to G. aristata. Plants in cultivation are usually intermediates and belong to Gaillardia x grandiflora.
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Selected literature:
Stoutamire W.P. (1960) The history of cultivated gaillardias. Baileya 8: 12-17.
Strother J.L. (2006) Gaillardia. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 21. Oxford University Press, New York-Oxford: 421-426.
Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.
Verloove F. (2006) Gaillardia x grandiflora. In: Van Landuyt W., Hoste I., Vanhecke L., Van den Bremt P., Vercruysse W. & De Beer D., Atlas van de flora van Vlaanderen en het Brussels gewest. Instituut voor Natuur- en Bosonderzoek, Nationale Plantentuin van België en Flo.Wer: 418.