Helianthus maximiliani

Helianthus maximiliani is a wide-ranging perennial herb found in prairies, fields, and waste areas, such as moist roadsides, ditches, and other disturbed areas. It occurs throughout much of temperate North America from Ontario west to British Columbia, Canada, and south to Georgia and New Mexico in the United States and northern Mexico, though it is only considered to be native in the midcontinental prairie regions (Manitoba to Alberta, Canada, south to Texas and New Mexico, United States, and Chihuahua, Coahuila, and Nuevo León, Mexico). There are over 1000 occurrences, which potentially face threats from development, conversion to agriculture or pasture, invasive species, and other threats in some places. Little is known about trends, but with a large range extent and large number of occurrences, abundant habitat, and broad habitat preferences, this species is considered secure.

Helianthus maximiliani occurs throughout much of temperate North America from Ontario west to British Columbia, Canada, and south to Georgia and New Mexico in the United States and northern Mexico (FNA 2006, Heil and O'Kane 2025, Weakley and the Southeastern Flora Team 2025). It is considered to be native in the midcontinental prairie regions (Manitoba to Alberta, Canada, south to Texas and eastern New Mexico, United States, and Chihuahua, Coahuila, and Nuevo León, Mexico), expanding eastward along railroads and highways (FNA 2006, Weakley and the Southeastern Flora Team 2025). It is also introduced in Ontario and Quebec (FNA 2006). Reports for California, Idaho, and Washington (FNA 2006) may be erroneous or based on cultivated material (see Calflora 2025, Idaho Department of Fish and Game 2025, Weinmann et al. 2025). Native range extent was estimated to be over 4 million square kilometers using herbarium specimens and photo-based observations documented between 1994 and 2025 (GBIF 2025, iNaturalist 2025, RARECAT 2025, SEINet 2025).

By applying a 1 km separation distance to herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1994 and 2025, it is estimated that there are over 1000 occurrences rangewide (GBIF 2025, iNaturalist 2025, NatureServe 2025, RARECAT 2025, SEINet 2025).

Although threats are not widely documented, this species is potentially threatened by development, conversion to agriculture or pasture, invasive species, and other threats in some places. However, their overall impact is likely negligible given the species' broad range and large number of occurrences.