Distribution
Species in the genus Helianthus are native to North America, but have very different distributions, varying from restricted (e.g., H. argophyllus and H. ludens) to widespread (e.g., H. annuus and H. tuberosus). In the U.S., some species are restricted to one or two states, such as H.carnosus in Florida, H. praecox in Texas, H. gracilentus and H. californicus in California, H. arizonensis in Arizona and New Mexico, and H. schweinitzii in North and South Carolina. Others, including H. annuus, H. tuberosus, and H. maximiliani, are found in most states of the U.S. A number of Helianthus species are regarded as threatened or endangered within certain states of the U.S.: H. angustifolius, H. carnosus, H. eggertii, H. giganteus, H. glaucophyllus, H. laevigatus, H. micro-cephalus, H. mollis, H. niveus, H. occidentalis, H. paradoxus, H. Schweinitzii, H. silphioides, and H. strumosus (USDA, 2006). Wild forms of H. tuberosus, on the other hand, are common and potentially invasive, especially in the eastern half of the U.S., being regarded as weeds in some situations. Escapes from cultivation (or plantings as food for wildlife) are also a common weed problem in Central and Eastern Europe, where it is often considered to be an invasive species (Balogh, 2001; Konvalinkova, 2003; Rehorek, 1997).
Jerusalem artichoke has predominantly been cultivated in North America and Northern Europe as a minor crop. The recent literature, however, includes reports of cultivation in China, Korea, Egypt, Australia, and New Zealand (e.g., Judd, 2003; Lee et al., 1985; Ragab et al., 2003).
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