Carelessweed (Amaranthus palmeri S. Watson)
Also known as dioecious amaranth, Palmer amaranth, Palmer's amaranth, Palmer's pigweed.
↑Range - Expand
| Legend | Color |
| Native | |
| Expanded | |
| Native or Not Present | |
| Native or Expanded | |
| Expanded or Not Present | |
| Native or Expanded or Not Present |
This tentative map is based on our own research. It may have limited data on Canada and/or Mexico, and there is some subjectivity in our assignment of plants as introduced vs. expanded. Read more in this blog post.
Although this plant occurs somewhere in each of these regions, it may only occur in a small part of some or all of them.
This species is also native to Mexico, and has expanded slightly eastward from its native range there; we have yet to build this portion of its range. We mark the new parts of this species' range in the US as Expanded because this is a weedy plant that spreads on its own, and because the regions where it is most dominant are adjacent to its native range, and the pattern introductions in the east are mostly separated from each other by shorter distances. Its range also may be fuller than county-level range maps suggest, due to the difficulty of identifying plants of the Amaranthus genus and the fact that this genus is often viewed generically as weeds and not given much attention on a more detailed level. This species has also been reported in Ontario, but we have yet to build this portion of its range map.
↑Faunal Associations
This species often occurs in cropland, where it absorbs excess soil nitrogen, which it concentrates in its foliage in the form of nitrates. These can be toxic to livestock, which will often browse it in spite of toxic levels of nitrates. This problem becomes more severe in the face of overfertilization, a problem that is widespread in commercial agriculture.
↑Control
This species has been introduced far outside its range and established in the wild in South America, Europe, North and East Africa, and South and East Asia. As this species has high invasive potential it is important to take care not to spread it to any areas outside its native range.
It is difficult to control as it has evolved resistance to a long list of herbicides, including glyphosate, 2,4-D, dicamba, ALS, atrazine, mesotrione, Huskie, Laudis, Impact, Armezon, and fomesafon. This resistance has arisen due to the intense selection pressure created by the use of these herbicides to control it in cropland where it is common.
Herbicide resistance typically evolves in isolated populations, but can be easily spread if seed is spread around by agricultural equipment. It is thus important to prevent such spread. In regions where this plant is common, however, such preventive measures may be ineffective because this plant is wind-pollinated.
↑Links & External Resources
• Amaranthus palmeri (Carelessweed) | USDA PLANTS Database (About This Site)
• Amaranthus palmeri | Go Botany (About This Site)
• Amaranthus palmeri (Palmer amaranth) | CABI Invasive Species Compendium (About This Site)
• Amaranthus palmeri | Biota of North America Project (BONAP) (About This Site)
• Amaranthus palmeri | NatureServe Explorer (About This Site)
• Amaranthus palmeri | Flora of North America (About This Site)
• Carelessweed | Maryland Biodiversity Project (About This Site)
• Amaranthus palmeri S.Watson | Plants of the World Online (POWO) (About This Site)
• Amaranthus palmeri S. Wats. (Careless-weed, Palmer's Amaranth) | Digital Atlas of the Virginia Flora (About This Site)
