1. Grindelia squarrosa (Pursh) Dun. (syn.: G. serrulata Rydb.) (N-Am.) – A very rare and always ephemeral alien. First recorded near a railway track in coastal dunes in Adinkerke in 1920 (close to a military base and probably introduced by American troops). Furthermore observed as a grain alien on the unloading quay of the Samga grain mill at the Amerikadok in the port of Antwerpen in 2005 and 2007.
Grindelia squarrosa is an increasing weed in parts of eastern Europe, including Romania (Sîrbu & Oprea 2008) and Ukraine (see Kharkhota 1976 and others).
Selected literature:
Kharkhota G.I. (1976) Nove mistseznakhodzhennya Grindelia squarrosa (Pursch) Dunal u Donbasi. (New occurrence of Grindelia squarrosa (Pursch) Dunal in Donbas). Ukr. Bot. Zhurn. 33(5): 545-546.
Sîrbu C. & Oprea A. (2008) Two alien species in the spreading process in Romania: Reynoutria x bohemica Chrtek & Chrtková and Grindelia squarrosa (Pursh) Dunal. Cercetări Agronomice Moldova XLI(2) (134): 41-50. [available online at: http://www.uaiasi.ro/CERCET_AGROMOLD/CA2-08-05.pdf]
Vladimirov V. & Petrova A.S. (2012) Grindelia squarrosa: a new alien species for the Bulgarian flora. Phytol. Balcan. 18(3): 315-318. [available online at: http://www.bio.bas.bg/~phytolbalcan/PDF/18_3/18_3_07_Vladimirov_&_Petrova.pdf]