Identifying Palmer amaranth
- Palmer amaranth has hairless stems. Redroot pigweed and smooth pigweed, on the other hand, have tiny, fuzzy hairs on the stems. On newer stem growth, these hairs often feel and appear similar to peach fuzz. However, as redroot pigweed plants grow, their hairs become less evident on the woody stems. So, find some young growth toward the top of the plant or the ends of branches to determine if the plant indeed does have hairless stems.
- If the plant has hairless stems, you can further confirm it’s identity as Palmer amaranth by examining the leaves. On Palmer amaranth, the petioles are often longer than the leaf blade itself. The petiole is the thin stalk that connects the leaf blade to the stem.
3. If the plant has produced seed heads and flowers (called influorescences), you can use them to readily distinguish Palmer. Palmer’s influorescences get quite long compared to those of other pigweeds. Redroot and smooth pigweed influorescences are small and clumped.
4. Sometimes, Palmer amaranth leaves have a single small hair at the tip of the their leaves.
5. Palmer amaranth leaves look quite similar to leaves of redroot and smooth pigweed. However, they can be distinguished from waterhemp by their shape. Palmer leaves are more rounded, while waterhemp leaves are relatively longer and slim.
Herbicide resistant populations:
- Group 2 + 9
- Group 2
- Group 3
- Group 5
- Group 9
- Group 14
- Group 27
- Group 9 + Group 14
- Group 5 + Group 27
- Group 5 + Group 9
Locations of resistant populations:
Alabama, Arizona, Arkansas, California, Delaware, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Minnesota, Mississippi, Missouri, Nebraska, New Jersey, New Mexico, North Carolina, Ohio, Pennsylvania, South Carolina, Tennessee, Texas, Wisconsin, Virginia