Dig deeper at SERNEC, a consortium of southeastern herbaria.

Read more about Rattlesnake-master at Vascular Plants of North Carolina.

The distinction between the two varieties, seemingly clear in NC and elsewhere in states bordering the Atlantic, seems to become less straightforward farther west..., per Weakley's Flora (2022)

SYNONYMOUS WITH PLANTS NATIONAL DATABASE:
Eryngium yuccifolium var. synchaetum   FAMILY Apiaceae

SYNONYMOUS WITH VASCULAR FLORA OF THE CAROLINAS (Radford, Ahles, & Bell, 1968) 140-04-003b:

Eryngium yuccifolium var. synchaetum   FAMILY Apiaceae

SYNONYMOUS WITH Manual of the Southeastern Flora (Small, 1933, 1938)

Eryngium synchaetum

COMMON NAME:
Southern Rattlesnake-master

NameThatPlant has no pictures at this time. You might try this link: Flora of the Southeastern United States

WEAKLEY'S FLORA OF THE SOUTHEASTERN US (4/24/22):
Eryngium yuccifolium var. synchaetum   FAMILY Apiaceae

SYNONYMOUS WITH PLANTS NATIONAL DATABASE:
Eryngium yuccifolium var. synchaetum   FAMILY Apiaceae

SYNONYMOUS WITH VASCULAR FLORA OF THE CAROLINAS (Radford, Ahles, & Bell, 1968) 140-04-003b:
Eryngium yuccifolium var. synchaetum   FAMILY Apiaceae

SYNONYMOUS WITH Manual of the Southeastern Flora (Small, 1933, 1938)
Eryngium synchaetum